CN101932190B - Measuring equipment and amplifying circuit, impedance component and multi-layer printed circuit board thereof - Google Patents

Abstract

The invention relates to measuring equipment and an amplifying circuit, impedance components and a multi-layer printed circuit board thereof. The measuring equipment comprises a multi-layer printed circuit board 220, a first resistor R21 and a second resistor R22, wherein the multi-layer printed circuit board 220 is provided with an element layer 221, an insulating layer 224, an insulating layer 225 and a shielding layer 223; the element layer 221 is provided with a first bonding pad 231, a second bonding pad 232 and a third bonding pad 233 which are used for arranging the first resistor R21 and the second resistor R22; and a middle layer 222 is arranged in the multi-layer printed circuit board 220, and parasitic capacitances C23, C24 and C25 introduced by the bonding pads 231 and 232 can be reduced or eliminated by changing the sizes of the first bonding pad 231, the second bonding pad 232 and the middle layer 222, the thickness as well as the dielectric constants of the insulating layers 224 and 225, so that the frequency characteristic of the circuit is improved. The measuring equipment and the amplifying circuit, the impedance components and the multi-layer printed circuit board thereof have the characteristics of stable property, simple design and easy realization.

Description

A kind of measuring equipment and amplifying circuit thereof, impedance compoment and multilayer board

Technical field

A kind of measuring equipment of the present invention and amplifying circuit, impedance compoment and multilayer board relate to amplifying circuit, resistor network or the multilayer board field of electric variable measurement equipment and employing thereof.

Background technology

Along with popularizing and development of surface mount process (SMT), the manufacture craft level of current measuring equipment is greatly improved, and the structure of measuring equipment is compact and small and exquisite more.But simultaneously, this technology has also been brought the problem of parasitic capacitance for measuring equipment, and particularly in order to eliminate electromagnetic interference, and under the situation that screen (stratum) is set on the printed circuit board (PCB), it is more serious that this problem just seems.Its reason is, can form parasitic capacitance between pad on the element layer of printed circuit board (PCB) and the screen, and these parasitic capacitances can influence the performance of measuring equipment.

As everyone knows, the parasitic capacitance on the printed circuit board (PCB) tends to make the amplitude-frequency characteristic variation of measuring equipment, and accuracy of measurement or measuring range descend.Therefore, how to eliminate or offset influence that parasitic capacitance produces and become the difficult problem that electric signal measurement institute must solution.

Specify SMT technology below and produce the principle of parasitic capacitance and the computational methods of parasitic capacitance.

Parasitic capacitance on the printed circuit board (PCB) is normally formed by two mutual insulatings and adjacent conductor; Such as; Referring to Fig. 1, on double-sided printed-circuit board 4, when element layer 1 has two adjacent conductive pads 6,7 with element layer 1, dielectric layer 2 and bottom 3; And when bottom 3 is the screen 5 that is made up of conductor, connect common port; Will form parasitic capacitance C1 between pad 6 and the pad 7, can form parasitic capacitance C2 between pad 6 and the screen 5, can form parasitic capacitance C3 between pad 7 and the screen 5.

See figures.1.and.2 in the lump, the pad on the printed circuit board (PCB) 46 is corresponded to line terminal 21, pad 7 corresponds to line terminal 22; Screen 5 corresponds to line terminal 23; Can obtain the equivalent electric circuit 24 of printed circuit board (PCB) 4, can find out, connect parasitic capacitance C1 between line terminal 21 and the line terminal 22 from circuit 24; Connect parasitic capacitance C2 between line terminal 21 and the line terminal 23, connect parasitic capacitance C3 between line terminal 22 and the line terminal 23.

Those skilled in the art just can calculate the capacitance of parasitic capacitance C1, C2 and C3 in the circuit 24 respectively according to known parasitic capacitance computing formula 1.

$C=\frac{{\mathrm{\ϵ}}_r\mathrm{\ϵ\; S}}{d}$ -----------parasitic capacitance computing formula 1

Wherein,

C is the capacitance of parasitic capacitance;

ε _rRelative dielectric constant for the dielectric that constitutes dielectric layer;

ε is a permittivity of vacuum;

S be two conductor pole plates over against area;

D is the thickness of dielectric layer.

Cooperate concrete instance to specify the influence that parasitic capacitance produces measuring equipment below.

Parasitic capacitance can exert an influence to multiple measuring equipment.Such as, multimeters such as A.C. voltmeter, ammeter, universal instrument, oscilloscope, signal generator, logic analyzer exert an influence, or also comprise other composite measurement instruments are exerted an influence.

Oscilloscope is one of the most common universal measurement equipment; Be commonly used to see the waveform of looking into and analyze measured signal; Measure each item index of said waveform, parasitic capacitance can exert an influence to described oscilloscope, such as; Parasitic capacitance tends to oscillographic frequency response characteristic is exerted an influence, as makes oscillographic bandwidth narrow down, make oscillographic frequency response curve unsmooth.

Referring to Fig. 3; Common oscilloscope all has attenuator circuit 31, and attenuator circuit 31 is exactly to be subject to one of parts of effect of parasitic capacitance most, and the bandwidth of this circuit tends to determine whole oscillographic bandwidth range; Oscillographic attenuator circuit 31 is a resistor network that is formed by resistance R 1 and resistance R 2 normally; Have input 32, output 33 and common port 34, wherein resistance R 1 is connected between the input 32 and output 33 of circuit, and resistance R 2 is connected between output 33 and the common port 34.The input 32 of oscillographic attenuator circuit 31, output 33 are connected in series between oscillographic signal input part and the sampled measurements parts; Described oscillographic signal input part is used for connecting measured signal, and described sampled measurements parts are used for measuring and showing measured signal.Described attenuator circuit 31 is used for the measured signal that is inserted by oscillographic signal input part is decayed, and makes its amplitude satisfy the measurement range ability of the sampled measurements circuit of back.

With reference to figure 4; When adopting surface mount process that resistance R 1 is installed with resistance R 2; Normally resistance R 1 and resistance R 2 are installed on the printed circuit board (PCB) 44 with dielectric layer 41, element layer 42 and screen 43; One first pad 45, second pad 46 and one the 3rd pad 47 are set on the element layer 42 of printed circuit board (PCB) 44, resistance R 1 is installed between first pad 45 and second pad 46, resistance R 2 is installed between second pad 46 and the 3rd pad 47.The via hole 48 that between element layer 42 and screen 43, also has a conduction, this via hole 48 are used to be electrically connected screen 43 and described the 3rd pad 47, make screen 43 and pad 47 equipotentials.

In conjunction with reference to figure 3,4; In the prior art, element layer 42 is normally formed by Copper Foil with screen 43, and wherein screen 43 is connected with common port 34 usually; Cooperate to cover the radome on the element layer 42, in order to of the influence of shield electromagnetic interference signal to attenuator circuit 31.

In the application that has, also can adopt more the printed circuit board (PCB) of multilayer that attenuator circuit 31 is installed, such as adopting 6 layer printed circuit boards.Under the situation that adopts 6 layer printed circuit boards, can also have a plurality of line layers between the element layer 42 of printed circuit board (PCB) 44 and the screen 43, all separate between each line layer and element layer 42, the screen 43 with dielectric layer.What need special instruction is as required, below screen 43, also can be provided with other line layer.

In the prior art, the raw material that constitute the dielectric layer 41 of printed circuit board (PCB) 44 can have multiple choices, and adopt different raw-material dielectric layers also can have different relative dielectric constants.

In this example, can form between first pad 45 and second pad 46 can form between parasitic capacitance C11, second pad 46 and the 3rd pad 47 can form between parasitic capacitance C13, second pad 46 and the screen 43 between parasitic capacitance C12, first pad 45 and the screen 43 and can form parasitic capacitance C14.

Because first pad 45 and second pad 46; Smaller between second pad 46 and the 3rd pad 47 over against area; The capacitance of parasitic capacitance C11, C12 compares parasitic capacitance C13 or parasitic capacitance C14 is little a lot, and the electric capacity theoretical value of parasitic capacitance C11, C12 generally is merely 10 ^-19～10 ^-20Therefore the pF magnitude, can neglect parasitic capacitance C11, the C12 influence to circuit.

After neglecting parasitic capacitance C11, C12, can obtain being installed in the equivalent electric circuit 51 of the attenuator circuit 31 on the printed circuit board (PCB) 44, with reference to Fig. 5.

In equivalent electric circuit 51, in conjunction with reference to Fig. 4 and Fig. 5, input 52 corresponding first pads 45, output 53 corresponding second pads 46, link 58 corresponding the 3rd pads 47, screen 43 respective signal common ports 54.Because; On printed circuit board (PCB) 44, screen 43 is electrically connected with described the 3rd pad 47 through a conductive via 48 as equipotential members, and conductive via 48 makes the 3rd pad 47 and screen 43 equipotentials; Therefore, there is not parasitic capacitance between the 3rd pad 47 and the screen 43.

Can find out that from equivalent electric circuit 51 capacitor C 13 is to be based upon between input 52 and the common port 54, can the partial pressure properties by resistance R 1, R2 not exerted an influence; And capacitor C 14 is to be connected in parallel with resistance R 2; Can influence the partial pressure properties of resistance R 1, R2, according to known amplitude-frequency characteristic computing formula, referring to following formula 2; Can draw out the frequency response characteristic 61 of the output voltage signal Uo of equivalent electric circuit 51, with reference to figure 6.

$\frac{\mathrm{Uo}\left(\mathrm{J\ω}\right)}{\mathrm{Ui}\left(\mathrm{J\ω}\right)}=K\·\frac{1}{1+\mathrm{J\ω}{C}_{14}R}$ -----------Shi 2

In the formula 2, $K=\frac{R_2}{R_1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009101486247E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2},R=\frac{R_1\&CenterDot;R_2}{R_1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009101486247E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2},$ ω is an angular frequency

Among Fig. 6, ${\mathrm{\&omega;}}_1=\frac{1}{R\&CenterDot;C_{14}},$ $R=\frac{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009101486247E00041.png,H2009101486247E00102.png"\; state="\{\{state\}\}">R</figure-callout>}}_1\&CenterDot;R_2}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009101486247E00041.png,H2009101486247E00102.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009101486247E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}.$

In conjunction with reference to Fig. 3, Fig. 5 and Fig. 6, because the influence of parasitic capacitance C14, when the frequency of the input signal Ui of the input 52 of equivalent electric circuit 51 is higher than break frequency ω ₁After, the amplitude of the output voltage signal Uo of the output 53 of equivalent electric circuit 51 reduces with the increase of the frequency of the input signal Ui of input 52 fast.Can see that thus parasitic capacitance C14 has produced influence to the bandwidth of the attenuator circuit 31 that is made up of resistance R 1 and R2, and the bandwidth of attenuator circuit 31 has been narrowed down.The bandwidth of attenuator circuit 31 narrows down and tends to influence whole oscillographic frequency characteristic, makes whole oscillographic bandwidth also narrow down.

Universal instrument also is the most frequently used electric variable measurement instrument; Be commonly used to measure parameters such as direct current or alternating voltage, electric current and resistance; The universal instrument that has can also be used to the performance of devices such as measuring diode, triode; What have can also be used to measuring physical quantitys such as temperature, pressure, and what have also can be used for measuring frequency and time index.Above-mentioned parasitic capacitance also can exert an influence to the frequency characteristic of the ac signal measurement of universal instrument, its bandwidth is narrowed down, or make its amplitude-versus-frequency curve become unsmooth.

Referring to Fig. 7, the range amplifying circuit 71 of universal instrument also is to be subject to one of circuit of effect of parasitic capacitance most.The range amplifying circuit 71 of universal instrument is a reverse amplification circuit that is connected into by resistor network R11, range resistance R 12 and operational amplifier 72 normally; Wherein, Resistor network R11 is connected between the reverse input end 74 of input 73 and operational amplifier 72 of amplifying circuit 71, and range resistance R 12 is connected between the output 75 of reverse input end 74 and amplifying circuit 71 of operational amplifier 72.The positive input 76 of described operational amplifier 72 connects common port 77; In practical application; Range resistance R 12 often can be made up of a plurality of resistance parallel with one another and selector switch, and described selector switch can be selected different resistance is inserted between the output 75 of the reverse input end 74 of operational amplifier 72 and amplifying circuit 71, thus; Can change the measurement range of range amplifying circuit 71 through the resistance of control break range resistance R 12.

In practical application, because the resistance of resistor network R11 is bigger, such as; In order accurately to measure and raising input impedance; Usually will select the precision resistance about 1Mohm for use, in order to solve the lower-powered problem of precision resistance, it is two resistance R 13 and resistance R 14 of series connection each other that resistor network R11 often will disassemble; Reducing the power consumption that each resistance R 13 and R14 are carried, or also comprise other reason.But, be two resistance R 13 and resistance R 14 of series connection each other in case resistor network R11 is disassembled, also just introduced the problem of parasitic capacitance for circuit.

In conjunction with reference to figure 7 and Fig. 8; Adopting surface mount process that resistance R 13 and resistance R 14 are installed in the 84 last times of printed circuit board (PCB) with dielectric layer 81, element layer 82 and a screen 83 that is connected with common port 77; Can on the element layer 82 of printed circuit board (PCB) 84, be provided with one first pad 85, second pad 86 and one the 3rd pad 87; Be used to make resistance R 13 to be installed between first pad 85 and second pad 86, resistance R 14 is installed between second pad 86 and the 3rd pad 87.

In the present example, can form between first pad 85 and second pad 86 can form between parasitic capacitance C21, second pad 86 and the 3rd pad 87 can form between parasitic capacitance C23, second pad 86 and the screen 83 between parasitic capacitance C22, first pad 85 and the screen 83 and can form parasitic capacitance C24.

In the present example; Because the 3rd pad 87 also is used for the reverse input end 74 of concatenation operation amplifier 72; The positive input 76 of operational amplifier 72 connects common port 77; The characteristic of the negative-feedback circuit that operational amplifier 72 is formed (empty short empty disconnected characteristic) makes and does not have parasitic capacitance between the two by the 3rd pad 87 and common port 77 equipotentials.

In the present example, because the area of the opposite face between first pad 85 and second pad, 86, the second pads 86 and the 3rd pad 87 is smaller, parasitic capacitance C21, C22 can be left in the basket.

After neglecting parasitic capacitance C21, C22; Can obtain being installed in the equivalent electric circuit 91 of the range amplifying circuit 71 on the printed circuit board (PCB) 84; In the lump with reference to Fig. 8 and Fig. 9, in equivalent electric circuit 91, input 73 corresponding first pads 85; Intermediate connection point 92 corresponding second pads 86 of resistance R 13 and resistance R 14, corresponding the 3rd pad 87 of the pin of concatenation operation amplifier 72 reverse input ends 74 of resistance R 14.

In the present embodiment, parasitic capacitance C23, the C24 of first pad 85 and 86 introducings of second pad are about 1pF.When resistance R 13=R144=500k Ω; Parasitic capacitance C24 makes that the amplitude-frequency response 101 of equivalent electric circuit 91 of universal instrument range amplifying circuit 71 is that the depression (signal attenuation) greater than-3dB (being equivalent to-30% error) appears in the position of 318kHz in frequency; With reference to Figure 10, so just make the frequency characteristic of universal instrument become unsmooth.

In the prior art, for general universal instrument ac voltage measurement function, usually requiring the bandwidth at-3dB place is 1MHz; Obviously, because the existence of parasitic capacitance C24, with reference to figure 9; The performance index of described universal instrument descend greatly, can't satisfy the above-mentioned market demand.For this reason, something must be done to, to eliminate the influence of parasitic capacitance C24 to the universal instrument frequency response, makes the frequency characteristic of universal instrument become level and smooth.

The parasitic capacitance that reduces or eliminate on the printed circuit board (PCB) has multiple to the method for the influence of channel frequency characteristic.

Such as, can know that according to the principle that parasitic capacitance produces the parasitic capacitance that produces on the printed circuit board (PCB) often all is associated with resistance.So, can reduce or eliminate parasitic capacitance on the printed circuit board (PCB) through reducing resistance value to the influence of channel frequency characteristic.But this method is feasible in some circuit design only.Such as, when resistance value has determined some parameter characteristics of circuit, during like DC characteristic, just can not arbitrarily change the size of resistance.Such as in order to improve oscillographic voltage measurement scope, the resistance of its input attenuation network must use the resistance of big resistance again, so that reduce to measure electric current, reduces when measuring the influence to circuit-under-test.In this case, it is just unworkable to reduce the method for resistance value.

The method of removing screen also can reduce parasitic capacitance.But this method can't be applied to the measuring circuit very responsive to electromagnetic interference, in these circuit; It is requisite often on printed circuit board (PCB), to increase the circuit screen; Such as oscillographic front-end circuit, the AC measurment circuit of probe circuit, universal instrument, certain measuring circuit that also comprises some other to electromagnetic interference ten minutes sensitivity are after its reason mainly is to remove the circuit shielding; Circuit is easy to disturbed by the external electromagnetic place, and certainty of measurement can descend greatly.Although also can the circuit of measuring equipment be placed sometimes in the shielding box that metallic plate or metal derby make; Replacement is provided with screen on printed substrate, but so, not only can obviously increase the cost of manufacture of equipment; The volume of increase equipment, and can make the assembling process of circuit complicated more.

In the prior art, in order to reduce or to eliminate parasitic capacitance on the printed circuit board (PCB) to the influence of channel frequency response, the most frequently used method is the method that in circuit, increases in order to the building-out capacitor of the influence of offsetting parasitic capacitance.

With reference to Figure 11, such as, in equivalent electric circuit 51,, and this building-out capacitor C111 is satisfied through an external building-out capacitor C111 between input 52 and output 53 $C111=\frac{R2}{R1}\&CenterDot;C14,$ Just can eliminate the influence of parasitic capacitance C14 to circuit.

Utilizing external building-out capacitor C111 can eliminate or reduce parasitic capacitance C14 is a known technology to the influence of circuit; Its operation principle is; In the circuit, resistance R 1, R2 and capacitor C 111 and capacitor C 14 have been formed an electric bridge, when the capacitance that makes capacitor C 111 satisfies $C111=\frac{R2}{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009101486247E00041.png,H2009101486247E00102.png"\; state="\{\{state\}\}">R</figure-callout>}1}\&CenterDot;C14$ The time, the electric current in 60 to two capacitor C 111 of tie point between two resistance R 1 and the resistance R 2 and the circuit of the tie point 59 between the C14 is zero, and at this moment, described electric bridge reaches balance, and parasitic capacitance C14 no longer influences the partial pressure properties of resistance R 1, R2.

Theoretically, utilize the method for external building-out capacitor C111 can play the effect of the parasitic capacitance C14 in the compensation equivalent electric circuit 51, and then improve the frequency response characteristic of equivalent electric circuit 51.But it is very big to implement difficulty, and its reason is:

1, can reach 20% variation because variation of temperature can make the dielectric constant of the dielectric layer of above-mentioned printed substrate produce maximum, this causes confirming exactly the size of building-out capacitor.Thereby, when making, there is the people that building-out capacitor is designed to tunable capacitor, but does so in this way to the parasitic capacitance compensation method, all brought difficulty for the application of equipment, production in enormous quantities.In order to solve the influence of temperature, also have the stable material of choose dielectric constant to make printed circuit board (PCB), but there is the high perhaps shortcoming of processing difficulties of cost again in this method to printed substrate.

2, the capacitance of common capacity cell be discontinuous and nominal data and real data between have tolerance, be difficult to find a building-out capacitor that just in time accurately equates with parasitic capacitance sometimes.

3, the capacity cell of electric capacity itself also has temperature characterisitic by way of compensation, and its temperature characterisitic often is difficult to be complementary with the temperature characterisitic of the parasitic capacitance of printed circuit board (PCB).

Summary of the invention

The present invention is in order to solve the problem that prior art exists, and the present invention has disclosed a kind of measuring equipment and amplifying circuit, impedance compoment and multilayer board.

A kind of multilayer board,

Comprise an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described first pad is used to be connected one first resistance with second pad,

Described second pad also is used to be connected one second resistance with the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have the intermediate conductive layer that an electricity suspends, and,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described first pad; Have at least a part of upright projection to fall in the described intermediate conductive layer, the upright projection of described second pad all falls in the described intermediate conductive layer.

In a kind of multilayer board of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of multilayer board of the present invention; Described equipotential members also can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

In a kind of multilayer board of the present invention; Can form first parasitic capacitance between described first pad and the described intermediate conductive layer; Can form second parasitic capacitance between described intermediate conductive layer and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

A kind of impedance compoment,

Comprise a multilayer board and a resistor network,

Described multilayer board comprises an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have the intermediate conductive layer that an electricity suspends, and,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described first pad; Have at least a part of upright projection to fall in the described intermediate conductive layer, the upright projection of described second pad all falls in the described intermediate conductive layer.

In a kind of impedance compoment of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of impedance compoment of the present invention; Described equipotential members can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.In a kind of impedance compoment of the present invention; Can form first parasitic capacitance between described first pad and the described intermediate conductive layer; Can form second parasitic capacitance between described intermediate conductive layer and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

A kind of amplifying circuit,

Comprise a multilayer board, a operational amplifier and a resistor network that is connected with described operational amplifier with positive input and reverse input end,

Described multilayer board comprises an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have the intermediate conductive layer that an electricity suspends, and,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described first pad; Have at least a part of upright projection to fall in the described intermediate conductive layer, the upright projection of described second pad all falls in the described intermediate conductive layer.

A kind of measuring equipment,

Comprise a multilayer board, a resistor network and a common port,

Described multilayer board comprises an element layer and a screen that is used to be connected described common port, and described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have the intermediate conductive layer that an electricity suspends, and,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described first pad; Have at least a part of upright projection to fall in the described intermediate conductive layer, the upright projection of described second pad all falls in the described intermediate conductive layer.

In measuring equipment of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In measuring equipment of the present invention; Described equipotential members can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad connects an input of described operational amplifier, and another input of described operational amplifier connects described common port.

In measuring equipment of the present invention; Can form first parasitic capacitance between described first pad and the described intermediate conductive layer; Can form second parasitic capacitance between described intermediate conductive layer and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

The present invention is in order to solve the problem that prior art exists, and the present invention has disclosed another measuring equipment and amplifying circuit, impedance compoment and multilayer board.

A kind of multilayer board,

Comprise an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described first pad is used to be connected one first resistance with second pad,

Described second pad also is used to be connected one second resistance with the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described first pad is connected through conductor with described intermediate conductive layer; In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

In a kind of multilayer board of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of multilayer board of the present invention; Described equipotential members can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

In a kind of multilayer board of the present invention; Can form first parasitic capacitance between described second pad and the described intermediate conductive layer; Can form second parasitic capacitance between described second pad and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

A kind of impedance compoment,

Comprise a multilayer board, resistor network,

Described multilayer board comprises an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

In a kind of impedance compoment of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of impedance compoment of the present invention; Described equipotential members also can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

In a kind of impedance compoment of the present invention; Can form first parasitic capacitance between described second pad and the described intermediate conductive layer; Can form second parasitic capacitance between described second pad and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

A kind of amplifying circuit,

Comprise a multilayer board, operational amplifier with positive input and reverse input end and a resistor network that is connected with described operational amplifier,

Described multilayer board comprises an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

A kind of measuring equipment,

Comprise a multilayer board, a resistor network, a common port,

Described multilayer board comprises an element layer and a screen that is used to be connected described common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

In a kind of measuring equipment of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of measuring equipment of the present invention; Described equipotential members also can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

In a kind of measuring equipment of the present invention; Can form first parasitic capacitance between described second pad and the described intermediate conductive layer; Can form second parasitic capacitance between described second pad and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

The present invention is in order to solve the problem that prior art exists, and the present invention has disclosed another measuring equipment and amplifying circuit, impedance compoment and multilayer board.

A kind of multilayer board,

Comprise an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described first pad is used to be connected one first resistance with second pad,

Described second pad also is used to be connected one second resistance with the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described second pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer, have at least a part of upright projection to fall in the described screen, in the upright projection of described first pad, have at least a part of upright projection to fall in the described intermediate conductive layer.

In a kind of multilayer board of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of multilayer board of the present invention; Described equipotential members also can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

In a kind of multilayer board of the present invention; Can form first parasitic capacitance between described first pad and the described intermediate conductive layer; Can form second parasitic capacitance between described intermediate conductive layer and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

A kind of impedance compoment,

Comprise a multilayer board, resistor network,

Described multilayer board comprises an element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described second pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer, have at least a part of upright projection to fall in the described screen, in the upright projection of described first pad, have at least a part of upright projection to fall in the described intermediate conductive layer.

In a kind of impedance compoment of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of impedance compoment of the present invention; Described equipotential members also can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

In a kind of impedance compoment of the present invention; Can form first parasitic capacitance between described first pad and the described intermediate conductive layer; Can form second parasitic capacitance between described intermediate conductive layer and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

A kind of amplifying circuit,

Comprise a multilayer board, operational amplifier with positive input and reverse input end and a resistor network that is connected with described operational amplifier,

Described multilayer board comprises

An element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described second pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer, have at least a part of upright projection to fall in the described screen, in the upright projection of described first pad, have at least a part of upright projection to fall in the described intermediate conductive layer.

A kind of measuring equipment,

Comprise a multilayer board, a resistor network, a common port,

Described multilayer board comprises

An element layer and a screen that is used to be connected described common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

Between described element layer and screen, also have an intermediate conductive layer, and,

Described second pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer, have at least a part of upright projection to fall in the described screen, in the upright projection of described first pad, have at least a part of upright projection to fall in the described intermediate conductive layer.

In a kind of measuring equipment of the present invention, described equipotential members can be to be made up of a conductor that connects described the 3rd pad and described screen.

In a kind of measuring equipment of the present invention; Described equipotential members can be to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.In a kind of measuring equipment of the present invention; Can form first parasitic capacitance between described first pad and the described intermediate conductive layer; Can form second parasitic capacitance between described intermediate conductive layer and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance can equal the ratio of described second resistance and described first resistance.

Measuring equipment of the present invention, amplifying circuit, impedance compoment or multilayer board; Utilization is arranged on the described intermediate conductive layer between described element layer and the screen; Not only need not to increase additional devices and just can improve or eliminate described parasitic capacitance, and have that temperature compensation characteristic is good, working stability, high reliability features.

Description of drawings

Fig. 1 is the structural representation of printed circuit board (PCB) 4 of the prior art.

Fig. 2 is the key diagram of the equivalent electric circuit 24 of printed circuit board (PCB) 4.

Fig. 3 is the key diagram of oscillographic attenuator circuit 31 of the prior art.

Fig. 4 is the structural representation that is used to install the printed circuit board (PCB) 44 of attenuator circuit 31.

Fig. 5 is mounted in the key diagram of the equivalent electric circuit 51 of the attenuator circuit 31 on the printed circuit board (PCB) 44.

Fig. 6 is the amplitude-frequency characteristic sketch map of equivalent electric circuit 51.

Fig. 7 is the key diagram of the range amplifying circuit 71 of universal instrument of the prior art.

Fig. 8 is the structural representation that is used to install the printed circuit board (PCB) 84 of range amplifying circuit 71.

Fig. 9 is mounted in the key diagram of the equivalent electric circuit 91 of the range amplifying circuit 71 on the printed circuit board (PCB) 84.

Figure 10 is the amplitude-frequency characteristic sketch map of equivalent electric circuit 91.

Figure 11 is the key diagram of the method for counteracting parasitic capacitance used in the prior art.

Figure 12 is the structure key diagram of the universal instrument 200 among first embodiment that selects for use of the present invention.

Figure 13 is the key diagram of reverse amplification circuit 203.

Figure 14 is the structural representation of the multilayer board 220 selected for use of first embodiment.

Figure 15 is the upright projection structural representation of multilayer board 220.

Figure 16 is mounted in the key diagram of the equivalent electric circuit 240 of the reverse amplification circuit 203 on the multilayer board 220.

Figure 17 is the key diagram of the further equivalent electric circuit 250 of equivalent electric circuit 240.

Figure 18 is the amplitude-frequency characteristic sketch map of equivalent electric circuit 250.

Figure 19 is the structure key diagram of the six-layer printed circuit board K that selects for use of first embodiment.

Figure 20 is the structural representation of the multilayer board 320 selected for use of first embodiment.

Figure 21 is mounted in the key diagram of the equivalent electric circuit 350 of the amplifying circuit 203 on the printed circuit board (PCB) 320.

Figure 22 is the structural representation of the multilayer board 420 selected for use of first embodiment.

Figure 23 is mounted in the key diagram of the equivalent electric circuit 450 of the amplifying circuit 203 on the printed circuit board (PCB) 420.

Figure 24 is the structural representation of the multilayer board 520 selected for use of first embodiment.

Figure 25 is mounted in the key diagram of the equivalent electric circuit 550 of the amplifying circuit 203 on the printed circuit board (PCB) 520.

Figure 26 is the key diagram of the amplifying circuit 601 of the oscilloscope 600 selected for use of second embodiment.

Figure 27 is the structural representation of the multilayer board 620 selected for use of second embodiment.

Figure 28 is the structural change key diagram of amplifying circuit 601.

Figure 29 is the structural representation of the multilayer board 630 selected for use of second embodiment.

Figure 30 is the structural representation of the multilayer board 640 selected for use of second embodiment.

Figure 31 is the structural representation of the multilayer board 650 selected for use of the second real-time example.

Embodiment

For a kind of measuring equipment of the present invention and parts thereof, the specific embodiment that the present invention selected for use of giving an example below further are described.

First embodiment:

With reference to Figure 12, in the present embodiment, measuring equipment of the present invention is a digital multimeter 200, and digital multimeter 200 comprises an input terminal 202, range amplifying circuit 201, an A/D converter 204 and a microprocessor 205.Input terminal 202 is used to connect outside measured signal; Range amplifying circuit 201 is used for the signal processing and amplifying is carried out in the measured signal from input terminal 202; A/D converter 204 is used for the signal of range amplifying circuit 201 outputs is carried out analog-to-digital conversion, and microprocessor 205 is used for the digital signal of A/D converter 204 outputs is carried out data processing.

As illustrating, in the present embodiment, can also include other circuit between input terminal 202 and the range amplifying circuit 201, like overvoltage and current foldback circuit, attenuator circuit etc.Also can include other circuit between range amplifying circuit 201 and the A/D converter 204, such as filter circuit, direct current is removed circuit or is also comprised ac-dc converter circuit etc.

In the present embodiment; Described microprocessor 205 can be to be constituted, also can be to be made up of CPU and FPGA or CPLD class programming device by CPU; Also can be to be made up of CPU and DSP, CPU be made up of instrument dedicated cpu or DSP, also can be made up of single-chip microcomputer.Certainly, for different application, microprocessor 205 also can be to be made up of computer, as being made up of personal computer.

In the present embodiment; Digital multimeter 200 is to be used to measure the multiple signal of telecommunication; Like direct voltage, electric current, alternating voltage electric current, resistance, or also comprise the universal instrument of devices such as can measuring electric capacity, diode, triode, for different application; Digital multimeter 200 can also comprise more measurement function, or reduces some measurement functions.

In the present embodiment, the range amplifying circuit 201 of digital multimeter 200 is to be made up of a reverse amplification circuit 203, please with reference to Figure 13.

Reverse amplification circuit 203 comprises an input 211, operational amplifier A 1, resistor network 219, range resistance R 23, an output 212 and a common port 244.Resistor network 219 is series between the reverse input end 216 of input 211 and operational amplifier A 1, and resistor network 219 is made up of with resistance R 22 resistance R 21 of series connection.Range resistance R 23 is connected between the output 214 of reverse input end 216 and operational amplifier A 1 of operational amplifier A 1; The positive input 215 of operational amplifier A 1 connects common port 244, and the output 214 of operational amplifier A 1 is connected to the output 212 of reverse amplification circuit 203.When an input signal Uin is linked into the input 211 of reverse amplification circuit 203, after reverse amplification circuit 203 is enlarged into output signal U out with input signal Uin, by its output 212 outputs.

With reference to Figure 14, in the present embodiment, also has a multilayer board 220.Multilayer board 220 is three layer printed circuit boards, comprises an element layer 221, a screen 223 and the intermediate layer 222 between element layer 221 and screen 223.

In the present embodiment; Element layer 221, intermediate layer 222 and screen 223 are made up of copper-foil conducting electricity; Be provided with an insulating barrier 224 between element layer 221 and the intermediate layer 222; Be provided with an insulating barrier 225 between intermediate layer 222 and the screen 223, insulating barrier 224 is made up of the dielectric material with insulating barrier 225.

In the present embodiment, the element layer 221 of multilayer board 220 comprises one first pad 231, second pad 232 and one the 3rd pad 233.Pad the 231,232, the 233rd, the Copper Foil pad.

In conjunction with reference to Figure 13 and Figure 14; In the present embodiment; First pad 231 of the input 211 corresponding multilayer boards 220 of reverse amplification circuit 203; The 3rd pad 233 of the reverse input end 216 corresponding multilayer boards 220 of operational amplifier A 1, the screen 223 of common port 244 corresponding multilayer boards 220, screen 223 are used for preventing that reverse amplification circuit 203 is disturbed by external electromagnetic field.Two pins of the resistance R 21 in the resistor network 219 of reverse amplification circuit 203 are installed on first pad 231 and second pad 232 with welding manner, and two pins of resistance R 22 are installed on second pad 232 and the 3rd pad 233 with welding manner.

In the present embodiment, intermediate layer 222 is arranged on the below of first pad 231 and second pad 232, and through with described element layer 221 and screen 223 electric insulations, forms the conductive layer of an electricity suspension.

Please with reference to Figure 15, in the present embodiment, the area in the intermediate layer 222 of multilayer board 220 is greater than the area of first pad 231 and second pad 232, and the upright projection of first pad 231 and second pad 232 all falls in the intermediate layer 222.The area of screen 223 is more than or equal to the area in intermediate layer 222, and the upright projection in intermediate layer 222 all falls in the screen 223.

Please combine again with reference to Figure 13 and Figure 14; In the multilayer board 220 of present embodiment; Can produce a parasitic capacitance C21 between first pad 231 and second pad 232, can produce a parasitic capacitance C22 between second pad 232 and the 3rd pad 233, can produce a parasitic capacitance C23 between first pad 231 and the intermediate layer 222; A parasitic capacitance C24 can be produced between second pad 232 and the intermediate layer 222, a parasitic capacitance C25 can be produced between intermediate layer 222 and the screen 223.Here need to prove; In the present embodiment; Because the reverse input end 216 of the 3rd pad 233 corresponding concatenation operation amplifier A1 is according to the positive input 215 and the reverse input end 216 equipotential known properties of operational amplifier A 1; The operational amplifier A 1 actual effect of playing an equipotential members, it makes the current potential of the 3rd pad 233 identical with the current potential of screen 223., there is not parasitic capacitance between the 3rd pad 233 and the screen 223 just because of the current potential of the 3rd pad 233 is identical with the current potential of screen 223 yet.

Please in the lump with reference to Figure 14, Figure 15 and Figure 16, owing to have parasitic capacitance C21, C22, C23, C24, C25, the reverse amplification circuit 203 that is installed on the multilayer board 220 can equivalence be equivalent electric circuit 240.In equivalent electric circuit 240; Node 241 is connected with input 211; Node 241 corresponds to first pad 231 in the multilayer board 220; Node 242 corresponds to second pad 232 in the multilayer board 220, and node 243 corresponds to the 3rd pad 233 in the multilayer board 220, and common port 244 corresponds to screen 223.

In multilayer board 220; Because less between first pad 231 and second pad 232, between second pad 232 and the 3rd pad 233 over against area; Parasitic capacitance C21, C22 are less with respect to parasitic capacitance C23, C24, C25, and its influence can be ignored.After neglecting parasitic capacitance C21, C22, can obtain the further equivalent electric circuit 250 of equivalent electric circuit 240, with reference to Figure 17.

Can know resistance R 21, resistance R 22, parasitic capacitance C23, C24, a C25 bridge circuit of actual formation (electric bridge) by equivalent electric circuit 250.In described bridge circuit, when only in parasitic capacitance C24, having electric current to flow through, parasitic capacitance C23, C24, C25 just can exert an influence to the frequency characteristic of the resistor network 219 be made up of resistance R 21 and R22.Can know according to the bridge balance principle, at this moment,, make like control parasitic capacitance C23, C25 $\frac{C23}{C25}=\frac{R22}{\mathrm{<figure-callout\; id="21"\; label="R"\; filenames="H2009101486247E00012.png"\; state="\{\{state\}\}">R</figure-callout>}21},$ Then can make the electric current on the parasitic capacitance C24 that flows through is zero.Thereby eliminate parasitic capacitance C23, C24 and C25 influence to the frequency characteristic of resistor network 219.

In the present embodiment, in conjunction with reference to Figure 14 and Figure 17, is S over against area when what suppose first pad 231 and intermediate layer 222 ₁, the thickness of dielectric is D in the insulating barrier 224 ₁, the relative dielectric constant of dielectric is ε in the insulating barrier 224 _R1, then the capacitance of parasitic capacitance C23 can basis $C23=\frac{{\mathrm{\&epsiv;}}_{r1}\mathrm{\&epsiv;}{S}_1}{D_1}$ Confirm; If intermediate layer 222 is S with screen 223 over against area ₂, the thickness of dielectric is D in the insulating barrier 225 ₂, the relative dielectric constant of dielectric is ε in the insulating barrier 225 _R2, then the capacitance of parasitic capacitance C25 can basis $C25=\frac{{\mathrm{\&epsiv;}}_{r2}\mathrm{\&epsiv;}{S}_2}{D_2}$ Confirm.This shows, through controlling over against area S ₁, S ₂, or through controlling the thickness D of insulating barrier 224,225 ₁, D ₂,, or through changing the relative dielectric constant ε of material adjustment insulating barrier 224,225 _R2, ε _R1, all can change the size of parasitic capacitance C23 and C25, when parasitic capacitance C23 and C25 are satisfied $\frac{C23}{C25}=\frac{R22}{R21},$ The electric current that then can make the parasitic capacitance C24 that flows through is zero, thereby eliminates parasitic capacitance C23, C24 and the C25 influence to the frequency characteristic of resistor network 219.

In the present embodiment, because the insulating barrier 224,225 of multilayer board 220 adopts identical materials to make, therefore, in the present embodiment, be through changing over against area S ₁, S ₂Size and the thickness D of insulating barrier 224,225 ₁, D ₂Parasitic capacitance C23 and C25 are satisfied $\frac{C23}{C25}=\frac{R22}{\mathrm{<figure-callout\; id="21"\; label="R"\; filenames="H2009101486247E00012.png"\; state="\{\{state\}\}">R</figure-callout>}21}.$

After utilizing said method to eliminate parasitic capacitance C23, C24 and C25 influence to the frequency characteristic of resistor network 219; The amplitude-versus-frequency curve 270 of reverse amplification circuit 203 becomes comparatively level and smooth; With reference to Figure 18, the bandwidth of reverse amplification circuit 203 can reach 1MHZ.

One as present embodiment illustrates, and the multilayer board 220 in the present embodiment can also be to adopt the multilayer board more than three layers to constitute.For example, this printed circuit board (PCB) 220 can adopt six-layer printed circuit board K to constitute, with reference to Figure 19.The ground floor K1 of six-layer printed circuit board K is set to element layer, and the 3rd layer of K3 of six-layer printed circuit board K is set to the position at place, intermediate layer, and the layer 6 K6 of this six-layer printed circuit board is set to screen.At this moment, the thickness of insulating layer between ground floor K1 and the 3rd layer of K3 is the thickness that has comprised insulating barrier 224a and insulating barrier 224b.Thickness of insulating layer between the 3rd layer of K3 and the layer 6 has comprised the thickness of insulating barrier 225a, insulating barrier 225b and insulating barrier 225c.In originally illustrating; Be arranged on the conductive layer that the 3rd layer of intermediate layer on the K3 suspends for electricity; With ground floor K1, layer 6 K6, and be arranged on line layer between ground floor K1 and the 3rd layer of K3, be arranged on any line layer electric insulation between the 3rd layer of K3 and the layer 6 K6.

Illustrate as another, this first embodiment also can select multilayer board 320 for use, please combine with reference to Figure 13, Figure 14 and Figure 20,

Be different from multilayer board 220; In multilayer board 320; The upright projection in intermediate layer 222 all falls in the screen 223; The upright projection of first pad 231 has only part to fall in the intermediate layer 222, and remainder drops in the screen 223, and the upright projection of second pad 232 all falls in the intermediate layer 222.

In originally illustrating since the upright projection of first pad 231 only some falls in the intermediate layer 222, remainder drops in the screen 223, therefore, parasitic capacitance C36 in addition between first pad 231 and the screen 223.After neglecting parasitic capacitance C21 and parasitic capacitance C22, can obtain to be installed in the equivalent electric circuit 350 of the reverse amplification circuit 203 on the multilayer board 320, with reference to Figure 21.

Can be known that by equivalent electric circuit 350 parasitic capacitance C36 equivalence is connected between the input 211 and common port 244 of reverse amplification circuit 203, it can not exert an influence to the frequency characteristic of resistor network 219 and amplifying circuit 203.

Illustrate as another, this first embodiment also can select multilayer board 420 for use, please combine with reference to Figure 13, Figure 14 and Figure 22,

Be different from multilayer board 220; In multilayer board 420; The upright projection in intermediate layer 222 all falls in the screen 223; The part of the upright projection of second pad 232 falls in the intermediate layer 222, and remainder drops in the screen 223, and first pad 231 is through conductive via 428 electrical connection intermediate layers 222.In originally illustrating, conductive via 428 is equivalent to an equipotential members, and it makes the current potential of first pad 231 identical with the current potential in intermediate layer 222., there is not parasitic capacitance between first pad 231 and the intermediate layer 222 just because of the current potential of first pad 231 is identical with the current potential in intermediate layer 222 yet.

In the present embodiment; Because only some falls in the intermediate layer 222 upright projection of second pad 232, remainder drops in the screen 223, therefore; Can have a parasitic capacitance C26 between second pad 232 and the screen 223; After neglecting parasitic capacitance C21 and parasitic capacitance C22, can obtain being installed in the equivalent electric circuit 450 that multilayer is installed in the amplifying circuit 203 on the printed circuit board (PCB) 420, with reference to Figure 23.

Can know that by equivalent electric circuit 450 resistance R 21, resistance R 22, parasitic capacitance C24, C26 constitute a bridge circuit.Through parasitic capacitance C24 and C26 are satisfied $\frac{C24}{C26}=\frac{R22}{\mathrm{<figure-callout\; id="21"\; label="R"\; filenames="H2009101486247E00012.png"\; state="\{\{state\}\}">R</figure-callout>}21},$ Then can be so that electric current is zero on the branch road 455, thus parasitic capacitance C24, C26 influence eliminated to resistor network 219.

In originally illustrating,, therefore can the frequency characteristic of resistor network 219 and reverse amplification circuit 203 not exerted an influence because parasitic capacitance C25 equivalence is connected between input 211 and the common port 244.

Illustrate as another, this first embodiment also can select multilayer board 520 for use, please combine with reference to Figure 13, Figure 14 and Figure 24,

Be different from multilayer board 220, in multilayer board 520, second pad 232 is through conductive via 528 electrical connection intermediate layers 222.At this moment, after neglecting parasitic capacitance C21 and parasitic capacitance C22, can obtain being installed in the equivalent electric circuit 550 of the amplifying circuit 203 on the multilayer board 520, with reference to Figure 25.

Can know that by equivalent electric circuit 550 resistance R 21, resistance R 22, parasitic capacitance C23 and parasitic capacitance C25 constitute a bridge circuit.Capacitance through control parasitic capacitance C23 and parasitic capacitance C25 makes $\frac{C23}{C25}=\frac{R22}{\mathrm{<figure-callout\; id="21"\; label="R"\; filenames="H2009101486247E00012.png"\; state="\{\{state\}\}">R</figure-callout>}21},$ Then can make on the branch road 555 electric current is zero, thereby eliminates parasitic capacitance C23, C25 exerts an influence to the frequency characteristic of resistor network 219 and reverse amplification circuit 203.

As explanation further; In originally illustrating; With reference to Figure 24 and Figure 25; Parasitic capacitance C23 also can not only comprise because pad 231 with respect to the parasitic capacitance that screen 223 produces, can also comprise the electric capacity that other reason causes, parasitic capacitance that exists such as the element of resistance R 21 itself or resistance R 21 are with respect to the parasitic capacitance of screen 223 generations.At this moment,, also can adjust the capacitance of parasitic capacitance C23 and parasitic capacitance C25, make through controlling thickness, the dielectric constant over against area, insulating barrier 224 and insulating barrier 225 in first pad 231 and intermediate layer 222 $\frac{C23}{C25}=\frac{R22}{\mathrm{<figure-callout\; id="21"\; label="R"\; filenames="H2009101486247E00012.png"\; state="\{\{state\}\}">R</figure-callout>}21},$ Making on the branch road 555 electric current is zero, thereby eliminates parasitic capacitance C23, C25 exerts an influence to the frequency characteristic of resistor network 219 and reverse amplification circuit 203.

Second embodiment:

In the present embodiment, measuring equipment of the present invention is an oscilloscope 600, and please with reference to Figure 26, oscilloscope 600 comprises an amplifying circuit 601, and amplifying circuit 601 is connected in series in the input circuit of oscilloscope 600 through input 611, output 612.In this amplifying circuit, has a resistor network 602 and an operational amplifier A 61 that is connected in series between input 611 and the output 612.Wherein, Resistor network 602 is attenuation networks that connected to form by resistance R 61 and resistance R 62; The measured signal that is mainly used in inserting decays, and resistance R 61 1 ends and input 611 link, and the positive input 614 of the other end and amplifier A61 links; One end of resistance R 62 connects the positive input 614 of amplifier A61, and the other end connects common port 613.In the present embodiment; The output 616 of operational amplifier A 61 connects the output 612 of this amplifying circuit 601; The output 616 of operational amplifier A 61 is connected with reverse input end 615; Make operational amplifier A 61 connect into drive circuit or be called buffer circuit, be used to subordinate's circuit drive current is provided.

With reference to Figure 27, in the present embodiment, also has a multilayer board 620.Multilayer board 620 is one three layer printed circuit board, comprises an element layer 621, a screen 623 and the intermediate layer 622 between element layer 621 and screen 623.

In the present embodiment; Element layer 621, intermediate layer 622 and screen 623 are made up of conductor; Be provided with insulating barrier 624 between element layer 621 and the intermediate layer 622, be provided with insulating barrier 625 between intermediate layer 622 and the screen 623, insulating barrier 624 constitutes by insulating material with insulating barrier 625.

In the present embodiment, the element layer 621 of multilayer board 620 has first pad 631, second pad 632 and the 3rd pad 633.Pad 631,632,633 is the Copper Foil pad.

Please combine with reference to Figure 26 and Figure 27, in the present embodiment, the resistance R 61 of forming resistor network 602 is installed on the multilayer board 620 with resistance R 62.Two pins of resistance R 61 are installed on this first pad 631 and second pad 632, and two pins of resistance R 62 are installed on this second pad 632 and the 3rd pad 633.The 3rd pad 633 is electrically connected with screen 623 through conductive via 629, and conductive via 629 makes the 3rd pad 633 and screen 623 equipotentials.

In the present embodiment, intermediate layer 622 is the conductive layers that electricity suspends, and is positioned at the below of this first pad 631 and second pad 632.The conductive layer that so-called electricity suspends is meant that intermediate layer 622 is directly not arrive the conductive layer that connects any voltage or telecommunications.

In the present embodiment, input 614, the three pads 633 of input 611, the second pads 632 corresponding operational amplifier A 61 of first pad, 631 corresponding amplifying circuits 601 and the screen 623 corresponding common ports 613 of multilayer board 620.Screen 623 is used to prevent the interference of external electromagnetic field.

In the present embodiment, the area in the intermediate layer 622 of multilayer board 620 is greater than the area of first pad 631 and second pad 632, and the upright projection of first pad 631 and second pad 632 all falls in the intermediate layer 622.The area of screen 623 is more than or equal to the area in intermediate layer 622, and the upright projection in intermediate layer 622 all falls in the screen 623.

In the present embodiment; Can produce a parasitic capacitance C61 between first pad 631 and second pad 632; Can produce a parasitic capacitance C62 between second pad 632 and the 3rd pad 633; Can produce a parasitic capacitance C63 between first pad 631 and the intermediate layer 622, can produce a parasitic capacitance C64 between second pad 632 and the intermediate layer 622, can produce a parasitic capacitance C65 between intermediate layer 622 and the screen 623.

Based on the principle identical with first embodiment of the invention; In the present embodiment; Can neglect parasitic capacitance C61 and C62 influence to circuit, and, through adjust first pad 631 in the upright projection area on the intermediate layer 622, intermediate layer 622 the upright projection area on screen 623 or also comprise dielectric thickness or dielectric constant through adjustment insulating barrier 624 and insulating barrier 625; Change the capacitance of parasitic capacitance C63 and C65, can make $\frac{C63}{C65}=\frac{R62}{\mathrm{<figure-callout\; id="61"\; label="R"\; filenames="H2009101486247E00023.png"\; state="\{\{state\}\}">R</figure-callout>}61}.$ When $\frac{C63}{C65}=\frac{R62}{\mathrm{<figure-callout\; id="61"\; label="R"\; filenames="H2009101486247E00023.png"\; state="\{\{state\}\}">R</figure-callout>}61}$ The time; The electric current that can make the parasitic capacitance C64 that flows through is zero; Capacitor C 63 and C65 equivalent series be connected between input 611 and the common port 613, thereby eliminated parasitic capacitance C63, C64, C65 influence the frequency characteristic of resistor network 602 and whole amplifying circuit 601.

Illustrate as another of present embodiment, please in the lump with reference to Figure 27 and Figure 28, this is the connected mode of amplifying circuit 601 for example with the difference of described second embodiment.In originally illustrating; In amplifying circuit 601; One end of the resistance R 61 in the resistor network 602 connects the output 616 of amplifier A61; The other end of resistance R 61 connects the reverse input end 615 of amplifier A61, and an end of resistance R 62 connects the reverse input end 615 of amplifier A61, and the other end connects common port 613.The positive input 614 of amplifier A61 is connected to the input 611 of amplifying circuit 601.

Originally illustrate and still adopt multilayer board 620; On multilayer board 620; Input 615, the three pads 633 and screen 623 corresponding common ports 613 of output 616, the second pads 632 corresponding operational amplifier A 61 of first pad, 631 corresponding operational amplifier A 61.

In originally illustrating,, make through changing the capacitance of parasitic capacitance C63 and C65 $\frac{C63}{C65}=\frac{R62}{\mathrm{<figure-callout\; id="61"\; label="R"\; filenames="H2009101486247E00023.png"\; state="\{\{state\}\}">R</figure-callout>}61},$ Can make electric current on the parasitic capacitance C64 that flows through is zero, and final parasitic capacitance C63 and C65 are based upon on the output 612 of amplifying circuit 601.In the present embodiment, through making $\frac{C63}{C65}=\frac{R62}{\mathrm{<figure-callout\; id="61"\; label="R"\; filenames="H2009101486247E00023.png"\; state="\{\{state\}\}">R</figure-callout>}61},$ Can improve the level and smooth degree of amplifying circuit 601 amplitude-frequency characteristics, but be helpless to improve its bandwidth, in some certain applications environment.

Illustrate as another, described second embodiment also can select multilayer board 630 for use, please combine with reference to Figure 26, Figure 27 and Figure 29,

Be different from multilayer board 620, first pad 631 of multilayer board 630 and the upright projection of second pad 632 partly fall in the intermediate layer 622, and the upright projection in intermediate layer 622 all falls in the screen 623.Particularly, the upright projection part of first pad 631 falls in the intermediate layer 622, and another part falls in the screen 623, and the upright projection of second pad 632 all falls in the screen 623.

In originally illustrating; A part of upright projection of cause first pad 631 drops in the screen 623; Thereby produced parasitic capacitance C66, but because, parasitic capacitance C66 is connected between input 611 and the common port 613; So parasitic capacitance C66 can not exert an influence to the frequency characteristic of resistor network 602.

Illustrate as another, please combine with reference to Figure 26, Figure 27 and Figure 30, the oscilloscope 600 among this second embodiment also can be selected multilayer board 640 for use.

Be different from multilayer board 620, the part of the upright projection of second pad 632 of multilayer board 640 falls in the intermediate layer 622, and another part falls in the screen 623.First pad 631 is electrically connected with intermediate layer 622 through a conductive via 628.

In originally illustrating, parasitic capacitance C65 equivalence is connected between input 611 and the common port 613, can the frequency characteristic of resistor network 602 not exerted an influence.In originally illustrating,, make through adjustment parasitic capacitance C64 and C67 $\frac{C64}{C67}=\frac{R62}{\mathrm{<figure-callout\; id="61"\; label="R"\; filenames="H2009101486247E00023.png"\; state="\{\{state\}\}">R</figure-callout>}61},$ Also can make parasitic capacitance C64 and C67 equivalence for being connected between input 611 and the common port 613, can not influence the frequency characteristic of resistor network 602 or amplifying circuit 601.

In originally illustrating, the upright projection of this first pad 631 also can be that part falls into or all falls into or do not fall in the middle of the intermediate layer 622.

Illustrate as another, please combine with reference to Figure 26, Figure 27 and Figure 31, the oscilloscope 600 among this second embodiment also can be selected multilayer board 650 for use.

Be different from multilayer board 620, this second pad 632 of multilayer board 650 is electrically connected with intermediate layer 622 through a conductive via 627.In originally illustrating,, make through adjustment parasitic capacitance C63 and C65 $\frac{C63}{C65}=\frac{R62}{\mathrm{<figure-callout\; id="61"\; label="R"\; filenames="H2009101486247E00023.png"\; state="\{\{state\}\}">R</figure-callout>}61},$ Also can make parasitic capacitance C63 and C65 equivalence for being connected between input 611 and the common port 613, can not influence the frequency characteristic of resistor network 602 or amplifying circuit 601.

As further specifying, in originally illustrating, the upright projection of first pad 631 also can be that part falls in the middle of the intermediate layer 622, and the upright projection of second pad 632 also can be that part falls into intermediate layer 622.

As further specifying; At the multilayer board described in this enforcement 620,630,640 or 650, the resistance R 61 and the resistance R 62 of last installation are to be made up of the pure resistance element, but; For different application, resistance R 61 also can be to be made up of other components and parts that comprise impedance with resistance R 62.

As further specifying; Multilayer board 620,630,640 or 650 described in this enforcement not only can be used for installing the resistor network 602 in the amplifying circuit 601; The whole amplifying circuit 601 that comprises amplifier A61 be can also be used to install, or other circuit or parts in the oscilloscope 600 can also be used to installing.

The method that present embodiment disclosed; Not only can be used to eliminate, weaken or improve the parasitic capacitance that produces owing to the pad reason on the printed substrate; Thereby improve bandwidth or other frequency characteristics of resistor network 602 or whole amplifying circuit 601; But also can be used for eliminating, weaken or improve owing to other reasons, like the parasitic capacitance of components and parts reason or the introducing of wiring reason.The method that those skilled in the art are disclosed according to the present invention can easier realize the present invention repeating no more here equally.

At above-mentioned each embodiment with in further illustrating, disclosed and how to have utilized the described intermediate conductive layer that is arranged between described element layer and the screen, improve or eliminate described parasitic capacitance.Utilize disclosed method, not only need not to increase additional devices and just can realize improving or eliminating the purpose of described parasitic capacitance, and have that temperature compensation characteristic is good, working stability, high reliability features.

The above; Be merely embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; Can expect easily changing or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention all should be as the criterion with the protection range of claim.

Claims (13)

1. a multilayer board comprises

An element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described first pad is used to be connected one first resistance with second pad,

Described second pad also is used to be connected one second resistance with the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

It is characterized in that:

Between described element layer and screen, also have an intermediate conductive layer, and described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

2. multilayer board according to claim 1 is characterized in that:

Described equipotential members is to be made up of a conductor that connects described the 3rd pad and described screen.

3. multilayer board according to claim 1 is characterized in that:

Described equipotential members is to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

4. according to claim 1,2 or 3 described multilayer boards, it is characterized in that:

Form first parasitic capacitance between described second pad and the described intermediate conductive layer; Form second parasitic capacitance between described second pad and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance equals the ratio of described second resistance and described first resistance.

5. an impedance compoment comprises

A multilayer board, resistor network,

Described multilayer board comprises

An element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

It is characterized in that:

Between described element layer and screen, also have an intermediate conductive layer, and described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

6. impedance compoment according to claim 5 is characterized in that:

Described equipotential members is to be made up of a conductor that connects described the 3rd pad and described screen.

7. impedance compoment according to claim 5 is characterized in that:

Described equipotential members is to be made up of an operational amplifier with positive input and reverse input end; Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

8. according to claim 5,6 or 7 described impedance compoments, it is characterized in that:

Form first parasitic capacitance between described second pad and the described intermediate conductive layer; Form second parasitic capacitance between described second pad and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance equals the ratio of described second resistance and described first resistance.

9. an amplifying circuit comprises

A multilayer board, operational amplifier with positive input and reverse input end and a resistor network that is connected with described operational amplifier,

Described multilayer board comprises

An element layer and a screen that is used to be connected common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

It is characterized in that:

Between described element layer and screen, also have an intermediate conductive layer,

And described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

10. a measuring equipment comprises

A multilayer board, a resistor network, a common port,

Described multilayer board comprises an element layer and a screen that is used to be connected described common port,

Described element layer has one first pad, second pad and one the 3rd pad,

Described resistor network comprises one first resistance and one second resistance,

Described first resistance is connected on described first pad and second pad,

Described second resistance is connected on described second pad and the 3rd pad,

Described the 3rd pad also is used to connect one makes described the 3rd pad and the equipotential equipotential members of described screen,

It is characterized in that:

Between described element layer and screen, also have an intermediate conductive layer, and described first pad is connected through conductor with described intermediate conductive layer,

In the upright projection of described intermediate conductive layer; Have at least a part of upright projection to fall in the described screen; In the upright projection of described second pad, a part of upright projection falls in the described intermediate conductive layer, and a part of upright projection falls in the described screen.

11. measuring equipment according to claim 10 is characterized in that:

Described equipotential members is to be made up of a conductor that connects described the 3rd pad and described screen.

12. measuring equipment according to claim 10 is characterized in that:

Described equipotential members is to be made up of an operational amplifier with positive input and reverse input end,

Described the 3rd pad is used to connect an input of described operational amplifier, and another input of described operational amplifier is used to connect described common port.

13., it is characterized in that according to claim 10,11 or 12 described measuring equipments:

Form first parasitic capacitance between described second pad and the described intermediate conductive layer; Form second parasitic capacitance between described second pad and the described screen, the ratio of described first parasitic capacitance and described second parasitic capacitance equals the ratio of described second resistance and described first resistance.

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