CN100468271C - Accurate pure AC voltage/current convertor with low noise - Google Patents
Accurate pure AC voltage/current convertor with low noise Download PDFInfo
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- CN100468271C CN100468271C CNB2006101142734A CN200610114273A CN100468271C CN 100468271 C CN100468271 C CN 100468271C CN B2006101142734 A CNB2006101142734 A CN B2006101142734A CN 200610114273 A CN200610114273 A CN 200610114273A CN 100468271 C CN100468271 C CN 100468271C
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Abstract
A pure AC voltage-current inverter of precise low noise type is prepared as carrying out stopping treatment on input voltage by stopping circuit then coupling said voltage to positive and negative inverters, generating two precise output currents with reversed polarities by symmetric constant current circuit and using them as bias currents of two said inverters being used to covert input AC voltage to be AC current, superposing AC current with constant bias current to obtain general output current, superposing output currents of two said inverters to counterbalance constant current component for obtaining pure AC output current.
Description
Technical field
The present invention relates to the voltage-power pack of pure interchange output, lay particular emphasis on signal quality characteristic such as noise, DC maladjustment, interchange bandwidth and AC impedance, belong to converting electrical signal or processing technology field (IPC G05F/H03F), and non-power or power technique fields.
Background technology
At resonance type micromechanical Sensitive Apparatus and dependence test instrument field,, need sometimes-kind of high performance ac current source, for the cross-correlation detection circuit provides high-quality reference signal for realizing the detection of weak periodic signal.The critical nature of this ac current source is output noise, output imbalance, motional impedance and exchanges frequency response.Consideration proposes following index than common situation: output current 0.1mA
P-p~ 10mA
P-p, surrender voltage 〉=5V
P-p, low-frequency range (0.1～10Hz) noise≤0.2nA
Rms, output imbalance≤0.1 μ A, motional impedance 〉=50k Ω, frequency of operation 5kHz ~ 5MHz.And this current source should be a current source (realize difficulty far above the suspension load current source) over the ground, and its output should be pure alternating current (realizing that difficulty is far above pulsating direct current electric current source).In addition, in the realization of the electromagnetic exciting principle of micro mechanical device, also to use the high-quality ac current source sometimes.
As the ac current source of signal source, can adopt the alternating-current voltage source driving voltage-power pack of individual features and realize.The AC signal source technology of voltage form is quite ripe, so key is voltage-power pack (hereinafter to be referred as V/I).V/I is the mimic channel that the voltage signal of input is transformed to current signal, i.e. voltage-controlled current source (VCCS) in the circuit network theory.
The V/I of the common pure alternating current of output comprises Howland current pump and the differential sampling feedback formula of output current current source.But be subjected to the restriction of operational amplifier GBW index, these schemes are difficult to obtain good high frequency characteristics.If improve high frequency performance and adopt broadband or video algorithms amplifier, can influence DC performance again.Because the comprehensive DC performance of broadband operational amplifier can't be equal to the precision operational-amplifier of bandwidth relative narrower eventually.
The V/I of tool advantage is exactly the single-transistor amplifier that is made of a field effect transistor (FET) aspect high frequency characteristics, comprises cascode configuration and common base configuration.This class circuit has good noisiness simultaneously, and circuit structure is extremely simple.Because the common base configuration high frequency characteristics is better, output impedance is higher, therefore select common base configuration single-transistor amplifier as technical foundation of the present invention.
Because the h of FET
OsThe restriction of parameter, the output impedance of single-transistor amplifier are still to dislike not enough sometimes.Increase degeneration resistors and constitute series current negative feedback single-transistor amplifier, can effectively strengthen output impedance, can also improve the linear bandwidth that also further improves simultaneously.Be exactly well-known Cascode (cascode-common-base circuit) in addition, as the part in the empty frame of Fig. 2 circuit.This circuit has the high input impedance charcteristic of the high output impedance characteristic and the cascode configuration of common base configuration concurrently, and has effectively suppressed the input Miller capacitance effect.Developed some other on this basis again and improved circuit, as Eduard
" Cascode of adjustment (RGC) " that proposes Deng people's such as people " high amplitude of oscillation high impedance MOS Cascode " and Howard C.Yang " active negative feedback cascode-cobasis current source " is as the part in the empty frame of Fig. 3 circuit.Cascode or RGC all can equivalences be " the compound FET " that an output impedance strengthens, and adopts FET in the original circuit of this " compound FET " replacement can significantly improve the output impedance characteristic of original circuit.
In addition, the discreteness of transistor characteristic parameter and drift are all very big, and be incorrect if the working point is provided with, and also can produce bigger non-linear.Increase constitutes the active feedback transistor V/I of basic model based on the active negative feedback network of operational amplifier, can effectively address these problems, referring to Fig. 1.Negative feedback has improved static accuracy greatly, and has improved the low frequency output impedance of circuit.
Single-transistor V/I still is that active feedback transistor V/I belongs to direct current V/I, and promptly output can only be often to be worth DC current or pulsating direct current electric current.For obtaining pure alternating current, must adopt two V/I, both output currents are superposeed, to offset DC component.The DC component of offsetting back " remnants " for assurance is enough little, i.e. output imbalance is enough low, and two V/I must have enough DC precision.Single-transistor V/I can't satisfy this requirement, therefore can only adopt active feedback transistor V/I.But active feedback transistor V/I is subjected to the restriction of operational amplifier GBW index equally, is difficult to obtain good high frequency characteristics.Key issue is, as long as the closed loop of direct current signal and AC signal overlaps in the circuit, just is difficult to effectively take into account DC performance and exchange performance.
U.S. Pat 5,815,012 1996.08.02 H02M 011/00 has proposed a kind of fully integrated high frequency V/I scheme, has high frequency characteristics and output impedance preferably.Yet this scheme has adopted active negative feedback, and the coincidence of the closed loop of direct current signal and AC signal, therefore still can not take into account DC performance to greatest extent and exchange performance.And this scheme has adopted current mirroring circuit, is difficult to adopt discrete component to be realized, must take monolithic integrated usually, promptly adopts asic technology, disposable input height, and a lot of occasions do not have such condition.
In a word, though existing various monotechnics all has advantage in a certain respect, all can't satisfy desired performance index comprehensively.Key is DC precision and the contradiction that exchanges between the bandwidth.
Summary of the invention
Technology of the present invention is dealt with problems and is: for solving above-mentioned DC precision and the contradiction that exchanges between the bandwidth, a kind of accurate low noise pure AC voltage-power pack is provided, make the part of decision DC precision relatively independent with the part that decision exchanges bandwidth, promptly determine the part of DC precision not hinder the AC energy, the part that decision exchanges bandwidth does not hinder DC performance yet, thereby realizes " DC performance with exchange performance take into account "; Taked some squelch measures in addition, reached finally that desired output noise is low, output imbalance is little and motional impedance with exchange performance index such as frequency response.
Technical solution of the present invention: accurate low noise pure AC voltage-power pack, be made up of block isolating circuit, symmetrical constant-current circuit, direct transform device and negative transducer, block isolating circuit carries out every straight processing back generation two-way ac voltage signal and exports respectively being coupled to the ac voltage input of direct transform device and the ac voltage input of negative transducer to input voltage signal; The symmetry constant-current circuit produces that one tunnel positive polarity often is worth electric current and one tunnel negative polarity often is worth electric current, positive polarity often is worth that electric current and negative polarity often are worth the size of current coupling and direction is opposite, positive polarity often is worth direction of current for flowing out output terminal, for the direct transform device provides required normal value bias current, negative polarity often is worth direction of current for flowing into output terminal, for negative transducer provides required normal value bias current; The direct transform device will be an alternating current from one road ac voltage signal linear transformation of block isolating circuit, obtain total output current after superposeing with normal value bias current, and total output current is pulsating direct current, and is positive polarity, and promptly direction of current is for flowing out output terminal; Negative transducer will be an alternating current from another road ac voltage signal linear transformation of block isolating circuit, obtain total output current after superposeing with normal value bias current, and total output current is pulsating direct current, and is negative polarity, and promptly direction of current is for flowing into output terminal; The output current of direct transform device and the output current of negative transducer be in the stack of the output terminal of described voltage-power pack, two accurate couplings and opposite polarity normal value current component is cancelled each other, thus obtain pure ac output current; Described direct transform device (3) is identical with negative transducer (4) structure, form by the single-transistor common base configuration amplifier that mainly constitutes by transistor and resistance, and adopt low noise constant reference voltage source to provide gate bias voltage, thereby obtain good dynamic output impedance, a-c cycle response and noisiness for transistor.
The present invention's advantage compared with prior art: guarantee DC precision with dark negative-feedback principle of operational amplifier and low noise precision operational-amplifier, and guarantee that with active feedback transistor V/I principle it does not hinder the AC energy; Guarantee to exchange bandwidth with common base configuration single-transistor V/I, but guarantee that with constant pressure and flow bias mode and AC coupling mode it does not influence the circuit DC precision.Promptly realize DC precision and exchanged taking into account of bandwidth.In addition, with single-transistor circuit and noise filtering technique common guarantee noiseproof feature.Experiment shows, adopts above-mentioned technology, and circuit of the present invention can be realized quite high output noise, output imbalance, motional impedance and exchange performance index such as frequency response with general-purpose device.
Description of drawings
Fig. 1 is the active feedback transistor V/I of basic model of explanation background technology;
Fig. 2 strengthens active feedback transistor V/I for the series impedance that the present invention adopts;
Fig. 3 strengthens active feedback transistor V/I for the RGC impedance that the present invention proposes;
Fig. 4 is a theory diagram of the present invention;
The basic embodiment schematic diagram that Fig. 5 proposes for the present invention;
The employing electric capacity that Fig. 6 proposes for the present invention is every the circuit diagram of the embodiment of straight principle;
Fig. 7 is the circuit diagram of the embodiment of first kind of transformer isolation principle of employing of the present invention's proposition;
Fig. 8 is the circuit diagram of the embodiment of second kind of transformer isolation principle of employing of the present invention's proposition;
The circuit diagram of the second kind of transformer isolation principle of employing that Fig. 9 proposes for the present invention and the embodiment of series impedance enhancement techniques;
The circuit diagram of the second kind of transformer isolation principle of employing that Figure 10 proposes for the present invention and the exemplary embodiments of series impedance enhancement techniques and RGC impedance enhancement techniques.
Embodiment
As shown in Figure 4, the present invention is made up of block isolating circuit 1, symmetrical constant-current circuit 2, direct transform device 3 and negative transducer 4, and 1 pair of input voltage signal of block isolating circuit carries out every straight processing back generation two-way ac voltage signal and export respectively being coupled to the ac voltage input of direct transform device 3 and the ac voltage input of negative transducer 4; Symmetry constant-current circuit 2 generations one tunnel positive polarity often is worth electric current and one tunnel negative polarity often is worth electric current, positive polarity often is worth that electric current and negative polarity often are worth the size of current coupling and direction is opposite, positive polarity often is worth direction of current for flowing out output terminal, for direct transform device 3 provides required normal value bias current, negative polarity often is worth direction of current for flowing into output terminal, for negative transducer 4 provides required normal value bias current; Direct transform device 3 will be an alternating current from one road ac voltage signal linear transformation of block isolating circuit 1, with obtain total output current after the stack of normal value bias current, total output current is pulsating direct current, and be positive polarity, be that direction of current is to flow out output terminal, negative transducer 4 will be an alternating current from another road ac voltage signal linear transformation of block isolating circuit 1, with obtain total output current after the stack of normal value bias current, total output current is pulsating direct current, and be negative polarity, be that direction of current is to flow into output terminal, the output current of the output current of direct transform device 3 and negative transducer 4 is in the output terminal stack of described voltage-power pack, two accurate couplings and opposite polarity normal value current component is cancelled each other, thus pure ac output current obtained.
As shown in Figure 5, direct transform device 3 is mainly realized voltage-current transformation by the single-transistor common base configuration amplifier that transistor Q31 and resistor R 31 constitute, transistor Q31 adopts P channel fet (or superelevation β value PNP transistor), the output cathode electric current, electric current flows out drain electrode, promptly so-called voltage-controlled " current source "; Negative transducer 4 is realized voltage-current transformation by the single-transistor common base configuration amplifier that transistor Q41 and resistor R 41 constitute, transistor Q41 adopts N channel fet (or superelevation β value NPN transistor), the output negative pole electric current, electric current flows into drain electrode, promptly so-called voltage-controlled " electric current remittance ".Manage to make two sub-transducer output DC component equal and opposite in directions, and the AC compounent phase place is identical, and both output currents are directly sued for peace, then DC component is offset, and the AC compounent stack obtains pure ac output current.For making transistor Q31 and transistor Q41 have correct voltage power supply point, adopt reference voltage source V31 and negative reference voltage source V41 to provide constant gate bias voltage respectively for the two.
In view of direct transform device 3 and negative transducer 4 structural symmetry, principle are identical, below be that example is analyzed only with negative transducer 4.The small-signal transfer characteristics of the single-transistor common base configuration amplifier in the negative transducer is i
Out=v
In/ (R
41+ 1/g
M41).G wherein
M41The forward direction mutual conductance of expression transistor Q41, i.e. y
FsEven adopt constant biasing to solve the precision problem of DC component, still there are three problems in this circuit: the error of the amplitude output signal that the FET parameter discrete causes; The temperature of the amplitude output signal that FET parameters of temperature coefficient causes is floated; The signal waveform distortion that the FET nonlinear characteristic causes.Preliminary solution is the resistance R that suitably increases feedback resistor R41
41, make 1/g
M41Reduce relatively.Further, can float by the sum of errors temperature of demarcation and software temperature compensation solution signal amplitude.Institute requires not harsh usually for the reference waveform signal degree of distortion at application, strengthening R
41The basis on, the suitable AC compounent i of oxide-semiconductor control transistors Q41 drain-source current
AC, make its peak I
ACMuch smaller than its DC component I
DC, promptly be enough to effectively control nonlinear distortion.Suggestion value: R
41〉=10/g
M41, I
AC≤ 0.1 ~ 0.3I
DC
Certainly, if R
41Increase, for reaching same i
ACAmplitude, v
InAmplitude also must corresponding increase.For small-signal MOSFET or JFET, conservative estimation g
M41=3mS, and get R
41=15/g
M41=5k Ω.If output current peak I
AC＜1mA, then corresponding v
InPeak value is no more than 5V, still can accept under prior art.But if I
ACFurther increase then required v
InAmplitude will be difficult for realizing.At this moment, the block isolating circuit before the suggestion translation circuit adopts the transformer isolation principle, and adopts step-up transformer.
For guaranteeing that direct transform device 3 and negative transducer 4 output DC components accurately mate, be respectively both by normal value constant current source 21 and negative normal value constant current source 22 bias current is provided.Normal value constant current source 21 provides normal value bias current for direct transform device 3, and output current is a positive polarity, and direction of current is for flowing out output terminal, i.e. so-called " current source "; Negative normal value constant current source 22 provides bias current for negative transducer 4, and output current is a negative polarity, and direction of current is for flowing into output terminal, i.e. so-called " electric current remittance ".The advantage of constant biasing is thoroughly to have eliminated the parameter discrete of FET and the adverse effect of drift, guarantees the stable of working point electric current.Simultaneously, transistor is selected the small-signal MOSFET or the JFET of correct bias for use, grid current is reduced to minimum, and input signal carried out every directly, the normal value component that can guarantee direct transform device and negative transducer output current accurately equals normal value bias current separately, thereby realizes " part that decision exchanges bandwidth does not hinder DC performance ".
Normal value constant current source 21 and negative normal value constant current source 22 are the active feedback transistor V/I with normal value reference input voltage, guarantee DC precision with the dark negative feedback by operational amplifier.Two normal value reference voltages are produced with reference to constant current source I20 and two coupling precision resistor R21 and R22 that are connected on its both sides respectively by same normal value.Sort circuit has outstanding power-supply fluctuation rejection, and the symmetry that often is worth reference voltage is irrelevant with the reference constant current source only by two precision resistor decisions, so be fit to very much the occasion of this needs symmetric reference voltage.
The employing of operational amplifier will inevitably influence the interchange performance of active feedback transistor V/I.Among the present invention active feedback transistor V/I only normal threshold voltage is transformed to normal value electric current, so its exchange transfer characteristics to circuit performance without any influence.But it exchanges output impedance r
oThen different.By Fig. 5, because of there is alternating voltage v in transistor Q41 source electrode
s=i
AC/ g
M41So flowing through the negative alternating current of the drain electrode of the transistor Q22 of value constant current source often is v
s/ r
oSo r
oMust in whole working band, keep stable to guarantee the amplitude flatness of circuit.And active feedback transistor V/I exactly has such characteristics: the high-frequency transfer (HFT) characteristic is subjected to the restriction of operational amplifier, but as long as suitable selector model and working point, and adopt Cascode or RGC " compound FET " to replace simple FET, referring to Fig. 2 and Fig. 3, then can effectively improve its high frequency output impedance, the requirement of " part of decision DC precision does not hinder the AC energy " according to the invention just.
On the basis of basic embodiment, pure AC voltage-power pack of the present invention is that needs are discussed on some parts or ins and outs or has multiple embodiment.
Because of direct transform device 3 and negative transducer 4 have all adopted suspension level structure, block isolating circuit 1 is necessary.Block isolating circuit 1 can adopt electric capacity every straight principle or transformer isolation principle.Electric capacity is simple every straight schematic circuit, has the advantage of volume, cost and operating frequency range aspect, and these three aspects are the deficiency of transformer isolation principle just also; The advantage of transformer isolation is can not only the isolated DC component, realize that level suspends, and have and isolate low frequency and broadband noise, inhibition common mode interference, realize function such as impedance matching, above also mentioning simultaneously and adopting step-up transformer is significant for the amplitude of improvement precision, temperature stability and nonlinear distortion etc.
Adopt electric capacity as shown in Figure 6, adopt two-stage electric capacity directly can effectively suppress the dc shift and the low-frequency noise of input voltage every C10 and C11 every the basic embodiment of straight principle.
Transformer then can adopt single secondary coil every straight principle, as shown in Figure 7, or two-pack sideline circle, as shown in Figure 8.The advantage of single secondary coil is that transformer device structure is simple, is convenient to type selecting or customization.The advantage of two-pack sideline circle is to make the noise of gate bias voltage that the single-transistor amplifier is become the common mode composition, thereby has effectively suppressed the output current noise that produces because of it.Therefore, exigent occasions such as noise, range stability and waveform distortion advise adopting second kind of transformer isolation principle in that frequency span is limited.
For further improving the output impedance of circuit, 4 on the AC signal path among Fig. 8 can be replaced with previously described Cascode or RGC " compound FET " respectively at crucial transistor Q21, Q22, Q31, Q41, promptly obtain as Fig. 9 and circuit shown in Figure 10.Corresponding relation is as shown in the table.
For constant current source I20 among each figure and the constant current source I30 among Figure 10, precision, temperature float with motional impedance etc. be not emphasis, key is noiseproof feature.Therefore, the constant current source that can adopt the short circuit of depletion type JFET grid source to constitute.But the JFET discreteness is too big, and device screening work is difficult to avoid usually, thus also can select current regulator diode for use, as 2DH series.In fact, if power quality is fine, voltage source precision and stability are also enough, can adopt the low noise resistor to replace the semiconductor constant current device fully.
Capacitor C25 and capacitor C26 are all compensation condenser, get 5pF ~ 100pF usually, and effect is a stability of guaranteeing negative feedback loop.In case of necessity, also can adopt more high capacity, for example 0.01 μ F forms 10ms even bigger RC time constant with resistor R 27 and resistor R 28 respectively, this moment, the effect of these two capacitors no longer was a stabiloity compensation, but effectively suppressed high frequency, intermediate frequency and even than the noise of low-frequency range.But this measure meeting is the time response of " passivation " circuit further, makes the interchange output impedance of active feedback V/I almost completely depend on the y of FET
OsParameter.At this moment, adopt Fig. 2 or Cascode or RGC " compound FET " shown in Figure 3 to replace simple FET, just seem particularly necessary.When less demanding, also can omit this two capacitors, but this obviously still belong to interest field of the present invention, and can not can be regarded as new circuit structure.
Resistor R 27 and resistor R 28 produce compensation or the LPF effect except that cooperating with capacitor C25 and capacitor C26, also respectively as the local current feedback resistance of transistor Q21 and transistor Q22, further strengthen the output impedance of active feedback V/I.When performance requirement is not high, also can omit this two resistors, with the simplification circuit, but this obviously still belongs to interest field of the present invention, and can not can be regarded as new circuit structure.
Capacitor C21, C22, C23, C24 all belong to the noise filtering capacitor.If the noisiness of used reference voltage source and resistor is all enough good, perhaps noiseproof feature is less demanding, also can omit, and with the simplification circuit, but this obviously still belongs to interest field of the present invention, and can not can be regarded as new circuit structure.
Resistor R 25 and resistor R 26 all are operational amplifier input bias current balance resistances, can omit usually, then should omit for the operational amplifier of certain model, but this obviously still belong to interest field of the present invention, and can not can be regarded as new circuit structure.
Transistor Q21, Q22, Q31, Q41 can select MOSFET or JFET for use, the whole FET that replaces of " compound FET " circuit that also available Cascode, RGC or other performance strengthen, so long as adopt the simple FET that replaces wherein of public circuit form, just can not can be regarded as new circuit structure, and still belong to interest field of the present invention.
Be the performance of real performance circuit of the present invention, the model of Primary Component must be selected meticulously.
Obviously, circuit of the present invention can adopt discrete device to realize, also can carry out monolithic integrated (possibly of partition capacitance device can't be integrated).If select discrete MOSFET for use, existing commercially available MOSFET device is mostly at power or switch application, thereby some characteristic relevant with the linear signal processing is desirable not to the utmost, thus should select miniwatt MOSFET as far as possible, and note the I in the device handbook
GSS, r
DS, f
T, C
Iss, C
Oss, C
RssEtc. parameter.If select discrete JFET for use, commercially available JFET is generally depletion type, and MOSFET is generally enhancement mode, should note the difference of the two required bias voltage.
Relevant speciality technician should understand the corresponding relation between FET and the bipolar transistor (BJT).FET among the present invention also can correspondingly replace with BJT, is about to N-MOSFET or N-JFET and replaces with NPN transistor, and P-MOSFET or P-JFET replace with the PNP transistor.The G of FET, D, S electrode be B, C, the E electrode of corresponding BJT respectively.For reducing the dc error that the BJT base current causes, its current gain (β value) height of should trying one's best.Can also adopt the compound circuit (Darlington circuit) of a plurality of BJT in case of necessity, to obtain higher β value.
For guaranteeing linearity, stability and the noiseproof feature of circuit, capacitor C21, C22, C23, C24, C25, C26 all should adopt the model that stability is high, loss tangent is low, adsorption effect is low, electric leakage is low, as high-performance organic film (polystyrene or teflon) capacitor, NPO/COG sheet monolithic capacitor or other high-quality signal capacitor for filter.
Precision resistor R21 and R22 have determined the matching of normal value constant current source 21 and negative normal value constant current source 22 output currents, thus should select high precision, low-temperature coefficient, low noise model for use, as precision coiling or metal film resistor.In fact, the precision of the absolute value of these two resistors is unimportant, and key is the matching degree of the two.When circuit layout designs, should make the two approaching as far as possible, approaching to guarantee the two temperature.If adopt the monolithic Integrated Solution to realize, then should give full play to the advantage that integrated circuit is realized device matching easily, improve the matching degree of the two.
Because of the DC performance of circuit depends on normal value constant current source 21 and negative normal value constant current source 22, the absolute value of reference voltage source V31 and negative reference voltage source V41 has error slightly, or certain temperature drift is arranged, and all can not influence the DC performance of circuit.The key index of reference voltage source V31 and negative reference voltage source V41 is noiseproof feature.So should select the low noise model, can take the filtering noise reduction measure in case of necessity.
Micromechanics Sensitive Apparatus field is the higher but frequency span relative narrower (as centre frequency ± 10%) of frequency of operation often, and lays particular stress on output noise and output impedance.This moment, typical embodiment was second kind of transformer isolation principle of selection, and adopted necessary impedance enhancement techniques, the i.e. described Fig. 9 of preamble or Figure 10 circuit.
Claims (10)
1, accurate low noise pure AC voltage-power pack, it is characterized in that: be made up of block isolating circuit (1), symmetrical constant-current circuit (2), direct transform device (3) and negative transducer (4), block isolating circuit (1) carries out every straight processing back generation two-way ac voltage signal and exports respectively being coupled to the ac voltage input of direct transform device (3) and the ac voltage input of negative transducer (4) to input voltage signal; Symmetry constant-current circuit (2) generation one tunnel positive polarity often is worth electric current and one tunnel negative polarity often is worth electric current, positive polarity often is worth that electric current and negative polarity often are worth the size of current coupling and direction is opposite, positive polarity often is worth direction of current for flowing out output terminal, for direct transform device (3) provides required normal value bias current, negative polarity often is worth direction of current for flowing into output terminal, for negative transducer (4) provides required normal value bias current; Direct transform device (3) will be an alternating current from one road ac voltage signal linear transformation of block isolating circuit (1), obtain total output current after superposeing with normal value bias current, and total output current is pulsating direct current, and is positive polarity, and promptly direction of current is for flowing out output terminal; Negative transducer (4) will be an alternating current from another road ac voltage signal linear transformation of block isolating circuit (1), with obtain total output current after the stack of normal value bias current, total output current is pulsating direct current, and is negative polarity, and promptly direction of current is for flowing into output terminal; The output current of the output current of direct transform device (3) and negative transducer (4) is in the stack of the output terminal of described voltage-power pack, two accurate couplings and opposite polarity normal value current component is cancelled each other, thus obtain pure ac output current; Described direct transform device (3) is identical with negative transducer (4) structure, forms by the single-transistor common base configuration amplifier that mainly is made of transistor and resistance, and adopts low noise constant reference voltage source to provide gate bias voltage for transistor.
2, accurate low noise pure AC voltage-power pack according to claim 1 is characterized in that: described block isolating circuit (1) adopt electric capacity every straight structure or transformer every straight structure.
3, accurate low noise pure AC voltage-power pack according to claim 2, it is characterized in that: described transformer adopts single secondary coil every straight structure, or two-pack sideline circle; Adopt two-pack sideline circle, the end a pair of of the same name of two secondary coils can be coupled respectively to the ac voltage input of direct transform device (3) and the ac voltage input of negative transducer (4), and another is coupled respectively to the transistor gate of direct transform device (3) and the transistor gate of negative transducer (4) to end of the same name.
4, accurate low noise pure AC voltage-power pack according to claim 1, it is characterized in that: described symmetrical constant-current circuit (2) is by suspension constant current source (I20), normal value constant current source (21) and negative normal value constant current source (22) are formed, normal value constant current source (21) and negative normal value constant current source (22) are the DC voltage-power pack with normal value input voltage, two normal value input voltages are taken from first precision resistor (R21) and second precision resistor (R22) two ends of the coupling that is connected on suspension constant current source (I20) both sides respectively, thereby guarantee the accurate coupling of two normal value input voltages, and effectively suppress the influence of power-supply fluctuation, two DC voltage-power pack structural symmetry and parameter matching, thus guarantee that finally two-way often is worth the accurate coupling of output current.
5, accurate low noise pure AC voltage-power pack according to claim 4, it is characterized in that: two accurate voltage-power packs in the described symmetrical constant-current circuit (2) all adopt the active feedback transistor voltage of operational amplifier-power pack principle, make the good dynamic output impedance of its DC precision that has the dark negative-feedback circuit excellence of operational amplifier concurrently and single-transistor common base configuration amplifying circuit, a-c cycle response and noisiness.
6, accurate low noise pure AC voltage-power pack according to claim 5 is characterized in that: the transistor in the active feedback transistor voltage-power pack in the described symmetrical constant-current circuit (2) all can be by the whole replacement of Cascode circuit.
7, accurate low noise pure AC voltage-power pack according to claim 4 is characterized in that: can be between suspension constant current source (I20) two ends in the described symmetrical constant-current circuit (2) and ground and first precision resistor (R21) two ends and each organic film condenser in parallel of second precision resistor (R22) two ends or NPO monolithic capacitor.
8, accurate low noise pure AC voltage-power pack according to claim 1, it is characterized in that: the first transistor (Q31) in the described direct transform device (3) adopts P type J-FET or P type MOSFET, and have the constant reference voltage of low noise source (V31), (Q31) provides gate bias voltage for the first transistor; Transistor seconds (Q41) in the negative transducer (4) adopts N type J-FET or N type MOSFET, and has the constant negative reference voltage of low noise source (V41), and (Q41) provides gate bias voltage for transistor seconds.
9, accurate low noise pure AC voltage-power pack according to claim 8 is characterized in that: described the first transistor (Q31) and transistor seconds (Q41) all can be by the whole replacements of Cascode circuit.
10, accurate low noise pure AC voltage-power pack according to claim 8 is characterized in that: can be at each organic film condenser in parallel or NPO monolithic capacitor between the output of described reference voltage source (V31) and negative reference voltage source (V41) and the ground.
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| GB201105400D0 (en) * | 2011-03-30 | 2011-05-11 | Power Electronic Measurements Ltd | Apparatus for current measurement |
| CN104199501A (en) * | 2014-08-25 | 2014-12-10 | 长沙瑞达星微电子有限公司 | High-output impedance current source circuit |
| CN107453611B (en) * | 2017-08-14 | 2023-09-15 | 浙江大学 | DC power supply noise conditioning circuit based on constant current source |
| CN111007913B (en) * | 2019-12-05 | 2021-11-30 | 北京东方计量测试研究所 | Circuit and method for improving stability of current source |
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| 新颖的CMOS差动式电压－电流变换器及其应用. 钱聪，李迎春.国外电子元器件. 1998 |
| 新颖的CMOS差动式电压－电流变换器及其应用. 钱聪，李迎春.国外电子元器件. 1998 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US10408191B2 (en) | 2016-03-21 | 2019-09-10 | General Electric Company | Wind pitch adjustment system |
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