TWI261414B - An improved analogue selector - Google Patents

Abstract

The present invention relates to analogue selectors, also known as analogue multiplexers, for audio equipment input source selection. The present invention provides an analogue input selector for selecting one of a number of analogue source devices. The selector comprises a plurality of input connections for coupling to the input sources, each said input connection being connected to a gain controller having at least zero and one or more non-zero gains, said input connection not including a semiconductor switch. Preferably the gain controllers are implemented using MOSFETs which are held at a voltage which is independent of the signal voltage.

Description

1261414 玫,发明说明: [Technology Employee City to which the invention belongs] Field of the Invention The present invention relates to an analog selector, also known as an analog multiplexer, 5 especially but not only implemented in an integrated circuit, For example, high-fidelity (hi-fi) is amplified into an audio device. BACKGROUND OF THE INVENTION Analog input selectors have a variety of applications including, for example, use in audio 10 entertainment devices, such as home high-fidelity audio equipment, in-vehicle entertainment equipment, and hand-held equipment, which provide a choice of audio sources under normal conditions. , for example, a heart player, a tape card, or a radio. These devices typically connect an audio input signal to one or more outputs: for example: headphones, amplifiers, (tape) recorders, and digitizers. This is typically implemented using an input selector library, one for each output. As device miniaturization increases, such analog selectors are typically implemented in integrated circuits (ICs) using MOSFET switching techniques. The MOSFET is used, for example, because it has a low leakage current compared to other types of transistor switching techniques. Figure 1 shows a typical circuit 20 configuration for an analog input selector with a design gain. Because different signal levels are provided by different types of analog sources, the use of designable or variable wheeling options, for example, 5 card cards can be long: for a few milli-Krms, and from the sound-----" Line, the output provides a typical 2Vms. There is a 1 selector switch for each input source, and the cm〇s gain selector switch is configured according to the selected 1261414, the “original signal level” . Therefore, regardless of its input, the output signal level of the selector should be similar. The problem with this configuration is that the use of the cm〇s type of switch in the IC will be substantially as distorted by the signal level as illustrated in Figure 2. This is: 〇S switch's electric shouting depends on the voltage from the pole to the gate and from the source to 2 a. The material voltage is not constant in the selection of the 11 switch, because; and the voltage and source voltage rise with the signal. And drop, and ask the pole voltage is related to the fixed power supply voltage. H丨... The solution to this problem is to increase the size of the selected (four) switch, so as to reduce the input impedance of the impedance in the circuit board. And ^Niu low-span and pole/source voltage, and thus reduce the relative effect of any modulation of this CMOS switch. However, larger switches require more - material, which increases cost and increases unwanted The parasitic capacitance, which for example causes the power supply to degrade. 15 Other solutions suggested for this problem are at M. Sato, K.

Suzuki, Τ·Suzuki and Κ·Akutsu, "A Volume and Tone Control IC for h Bu Fi Audio", IEEE J Solid-State Circuits, Vol 16, No. 6, Dec 1981. p682-688. This document shows the use of very high sheet resistance materials for the gate electrodes. Then, the local gate is electrically connected to the channel at a frequency of "number" to maintain a substantially strange gate channel voltage. However, this requires an unusual manufacturing step, which increases the cost and the processing is not It is easy to implement. It also causes delays when switching from one channel to another, and therefore does not adopt this concept. Another solution is in T L. Bro〇ks et al. "a 1261414

Cascaded Sigma-Delta Pipeline A/D Converter with 1.25MHz Signal Bandwidth^ in IEEE Journal of Solid-State

Circuits, Vol.32, Νο·12, Dec 1997, especially on page 1901-2. It uses a charged die structure to effectively increase the gate voltage across the supply voltage depending on the previously sampled signal level 5 in an attempt to maintain a source/thinance voltage differential that is substantially constant to the gate. However, this structure results in the need for an idle time t pulse 'which itself can be a source of distortion and switching transients added to the signal. The extra reproducibility of the circuit also increases the chip area and therefore increases the cost. This involves raising the voltage higher than the normal supply voltage by means of a charge pump, which creates a risk of reliability for any circuit that switches and drives the switch. SUMMARY OF THE INVENTION Summary of the Invention In general, it is an object of the present invention to provide an analog selector that will be used in the basin by holding the secret or secret terminal as determined or with (4) a non-social voltage such as grounding « In the case of a transistor switch, the gate of the transistor of 〇sfet 15 is kept constant for the voltage of the source or gate to the drain. , meaning that the voltage does not change with the signal voltage. ° Ai Jingjing is achieved by replacing the connection between each input connection (10) for each input connection. This is used to select the switch between the gain stages of the selected input channel. This is used for the m〇sfet switch of the gain stage of the selected wheel input channel. Operates with a turn-on (.n) and two other voltages associated with the power supply to provide the source and the gate-to-gate voltage of the real 5, f疋. By removing the floating voltage select switch, substantially removing Distortion caused by the source-to-gate and drain-to-gate voltages, and the switching resistance of the switch 12 1261414. For illustrative purposes, the drain, source, and gate are used for simplicity and clarity. Description, but intended to include a corresponding structure having a similar function in a non-FET switch. For example, the term 'source and gate 5' is intended to include: collecting in a double-carrier junction transistor , an emitter and a base structure, and a similar structure having the same function in other types of semiconductor devices. In particular, an analog selector as in the first aspect of the patent application is provided in the viewpoint of the present invention. The analog connection stage input stage does not require a selector switch for each input, and therefore removes an important source of distortion. This switching function is now implemented by the input gain stage or controller. However, large selections are typically used. Switch to reduce distortion depending on the signal level, and further increase the physical size by 15 by the layout precaution to allow them to withstand the directly applied ESD and latching stress, which is removed by this configuration. The valuable 1C material can be saved. These gain stages or controllers preferably include one or more semiconductor switches each having a source or drain connected to the selector ground. This configuration provides the source to the gate of the switch. The pole voltage and the drain voltage to 20 gate voltage are used as the substantial grounding relative to the supply voltage rather than the signal voltage. Since a small switching structure can be used, this configuration uses a relatively small amount of 1C material because these switches are essentially The signal current is not carried and is not directly exposed to external ESD or latch stress. In an embodiment, the selector includes, for example An input and an output for an amplifier of an operational amplifier (op 1261414 amp), and each gain stage or controller further includes: an impedance chain connected between the output of the amplifier and each input connection, the switches are connected between the chains Between the amplifier inputs and the amplifier inputs, each of the gain stages may include a dedicated amplifier such that the entire input amplifier stage of each of the channels is repeated and switched in as needed. Typically implemented as a series of discrete impedance I, such as a resistor, along which, for example, a chain connected between discrete impedances, different combinations of impedances can be drawn at different points. This allows for the use of, for example, a series of resistors. The impedance chain selection is increased by a factor of 10. These switches are connected between the resistor connection and the amplifier input. If these switches are both open (zero gain), the input signal is cut off. 15 In a deuterated configuration, one or more of the gain controllers may include: only /, the switch has an impedance connected between the switch and each input, and the connection is between the output of the switching amplifier Other impedance. This configuration provides two settings: zero (jing) and non- (conduct); and this is done, the choice of the input is ☆, and there is no adjustable non-zero gain. ... — Straight, used to short the > class to the reference voltage when gaining. This reduces the possibility of losing electricity (4). j U f phase & clothing 乂 包括 includes the connection between the impedance chain and the reference band 3 =. The rose device preferably has a connection to the reference voltage::in: for: when the integrated circuit is executed, the short circuit is installed outside the switch, and the social device is connected to the device „connected to = 20 1261414 voltage. These selector switches do not substantially pass the signal current and can be physically small. The short-circuit switch resistance is not required to be large because they are not in the direct signal path. In either case, the NMOS or PMOS is turned on. 5 is sufficient to occupy a small amount of 1C material. A second aspect of the present invention is to provide a multiplex programmable gain amplifier that includes a plurality of input connections for connection to a plurality of input sources. Each input connection is connected to a programmable A gain stage having at least zero and one or more non-zero gains. Each programmable gain stage preferably has one or more semiconductor 10 switches, each having a non-gate input connected to the ground of the selector. The program gain stage preferably has an impedance chain connected between the amplifier output and each input connection. These switches are connected between the chain and the amplifier input. Other implementations and advantages of the present invention The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are illustrated by way of example only, and not by way of limitation. FIG. Known structure; Figures 2a-2d show schematic views of a CMOS device, and conductive features for various operations of the device; Figure 3 shows a structure for an analog selector in accordance with an embodiment of the present invention; Figure 4 shows the structure according to another embodiment; Figure 5 shows the enhancement of the structure of Figure 4; Figure 6 shows another enhancement of the structure of Figure 5; and 10 1261414 "° indicates the reference voltage source Buffer circuit. [Implementation of winter style] The detailed description of the preferred embodiment is shown in Fig. 1, which shows a known analog selector or multiplexer structure. Several selectors l〇i, l〇 Ii is typically incorporated into an audio device or the like to connect signals from, for example, a CD player to a microphone; several types of input sources 1 to a number of rounds. Each selector 10 includes a plurality of input connections 11 for connection to Input source 1. Each input source 1 Also connected to other selectors 10 to allow for multiplexing between the input source and output of the audio device. 10 Each connection 10 has a select or input switch 12a-12c with a separate input connection 11a-llc on one side. Connected to a respective input source ia-ic. The other side of each input switch 12a-12c is connected to a resistor chain or string 13 comprising a plurality of discrete resistors 13a-13n connected in series. The other end of the chain 13 is connected to The output of the operational amplifier (op amp) 15 (Vo), which also provides the output 15 from the selector circuit 1. A plurality of gain switches 143-141^ are tapped from the resistor chain 13, each from the resistor 13a- The connection between the two resistors in 13n. The other end of these switches 14 is coupled to the inverting input (I) of operational amplifier 15. By varying the on/off state of the gain switches 14, the signal gain provided by the operational amplifier 15 is varied by the negative feedback configuration provided by the resistor/switch 20 network. Therefore, for a high level input source 1, the gain of the operational amplifier can be reduced so that the normalized output signal level (Vo) can be provided by the selector 10 regardless of the level of the input source, typically only such Switch 14a - close. For example, 1261414 If switch 14b is off, then the gain is:

Vout/Vin = -(R13 c+R 13 d+... +R13 n)/(Rs+R 12 c+R 13 a+R 13 b) Vout=Output signal voltage amplitude at node (Vo) Vm= The input signal voltage amplitude generated by the same signal voltage source (lc) is 5 Rs = the same signal source impedance (lc and 2c) R12c, R14b = the on-resistance of the MOSFET switch (12c and 14b) R13a, R13b = each resistor Ri3a, The resistor of R13b can theoretically turn off one or more of these switches and short the segments of the pen resistor key 13 to provide an additional gain setting. However, it is actually simple to keep the operation by selecting only one off at a time. Figure 2a shows a CMOS transfer gate device comprising a PMOS portion and an NMOS portion, and is typically used in the switch implementation (12, 14) of the selector 1 described above. The device (12, 14) includes a source S and a drain D, 15 connected to other circuit elements in the selector 10, and PMOS and NMOS gates Gp and Gn to control the device _^PM〇s and Conductive of the NM0S part. When the PMOS gate Gp is high (+ve supply, vdd) and the NMOS gate Gn is low (-ve supply, ground), then the nm〇S and PMOS portions of the device are off (off) . When the PMOS gate is at a low potential and the NMOS gate 20 is at a high potential, both portions are turned on. In addition, when :: and the pole D and the source S are grounded (or less than the pmos threshold voltage Vtp above the ground potential) 'this PMOS portion is cut off (0, and when; and the pole and source are At vdd (or less than this +ve power supply from the NMOS threshold voltage Vtn), the NMOS portion is cut. These characteristics are shown in Figure 12 1261414 in Figure 2b. This drain-source conduction changes with the drain and source voltages. In other words, the conduction characteristics of this device vary with the voltage at the drain and source. Please refer to Figure 1 again. The selection of the switching device 12a-12c 5 and the voltage and source voltages change with the input signal, which causes the gain of the circuit to change as the input signal goes higher and lower (as in the above example, R12c is relative to Rs+R13a). +R13b changes), that is, causes voltage gain modulation depending on the signal. This causes distortion of the output signal. Figure 2c shows the characteristics of the CMOS transmission gate used in portable audio equipment, its power supply voltage (Vdd) Typically lower than non-portable devices to protect battery life It can be seen that this device is actually cut off for certain levels of the input voltage, causing more distortion. This problem can be mitigated to some extent by adding some steps to the manufacturing process, which allows for selection. The threshold voltage of the transistor is reduced from a normal 15 800 mV to, for example, 300 mV. This CMOS switch including this low threshold transistor will have some of the improved features as shown in Figure 2d. However, when temperature and normal manufacturing are exceeded Tolerance, this transistor can start conducting or at least a large amount of leakage when Vin (at node 11a, llb...) = Vdd or ground. If a large audio signal is applied to an unselected input, 20 or if accidentally or Deliberately shorting the input to ground or power, or even when the device is attached or removed to an external terminal, this can cause the interfering signal to overlap to the audible penetration of the selected audio signal. This effect does not occur for purely mechanical switches, which is unacceptable to many users. 13 1261414 Figure 3 shows an analogy according to a first embodiment of the invention The selectors 2 are each connected to a number of input sources la-lc via input connections 21a-21c. Each input connection 2la-21c is coupled to a respective gain controller 22 core 22c. Each of the control controls 22a-22c includes each An impedance key having, for example, a 5 dry discrete impedance 23a-23n of the resistor. The gain switches 243-241 are tapped from an impedance chain between the resistors 23a-23n and the inverting input (I) of the operational amplifier 25. The output (Vo) of the operational amplifier 25 is connected to each of the gain controllers 22 (at a 黾 resistance of 23 η) to form a negative feedback loop for input signal amplification. By controlling these gain switches 24, a different number of resistors 23 can be switched into the 1〇 feedback loop and the signal input path to control the input signal gain. This gain is determined as described above with respect to the circuit of Figure 1. By turning all of the gain switches 24 of the gain controller 22 open, this signal from the corresponding input source 1 cannot be transferred to the operational amplifier 25 and is therefore not amplified (zero benefit). By having only one gain controller (22c) 15 with a closed (g〇sed) gain switch (preferably only one of 24ca-24cn), only the corresponding input source 1 (: is transmitted to be used for amplification) The operational amplifier 25. Therefore, the gain switch 24 also functions as an input selector. The plurality of gain controllers 22 are each connected to a respective input source 1 to implement a wheel selection function and a gain control function, and The process of removing the selector or input switch (12) used in the configuration of Figure 1 is removed. This removes the gain depending on the signal level, and thus the associated wheel-out signal distortion. 24 is the inverting wheel (1) connected to the high-impedance op amp. We do not transmit any signal current (except for the negligible amount required to drive the small-input capacitor (1) pf of the large 12 (10). Moreover, since the = switch is connected to the ground, the source voltage and the immersion voltage of each CM 〇 are determined, and are related to the supply voltage and not related to the signal level, so the on-resistance is independent of the signal. Therefore, the CMOS switch Ό, 屯 resistance chain 23 can be used together to occupy a small amount of 1C material. In fact, when the transistor is turned on, the source and the gate voltage are known and valued, so that the CMOS switch can be replaced by the Lancome fine switch, and the omitted transistor and its redundant drive circuit and internal connection are further saved. area. Moreover, if these switches are all NM〇s, the input signal can vibrate the supply voltage exceeding ·1〇, and the parasitic drain _ substrate diode of the PMOS (currently omitted) is not biased. Press to avoid the circuit may be locked or damaged when turned on or off, and allow for large spike input signals. The input switch in Figure 1 usually needs to pass the input signal, which has a voltage from the near positive supply voltage to the near negative supply voltage, so the open- 15 off must be a CMOS switch, ie, parallel nm 〇 ^ pm s. However, the gain selection switch and the short-circuit switch of this embodiment have fixed drain and source voltages, so only NMOS or PMOS is required for each switch, and the number of electric_crystals can be halved, and the switches are removed. The need for complementary drive signals, thus reducing the area and cost. -0 Other advantages can be seen by returning to Figure 1, which is an external connection or pin that is directly connected to the integrated circuit. This means they can be exposed directly to external stresses such as ESD pulses or accidentally applied current pulses. These inputs typically must withstand at least 2 kV pulses and ±200 mA of injection current without locking or permanent damage. Some stresses 15 1261414 can be absorbed by the protective diode from the input to the power supply but because the input diffusion is directly connected to the pin, approximately half of the stress typically must be absorbed in the switch. Thus, the input switch transistor 12 is larger than normal (eg, from metal contact to input diffusion to the transistor gate) and will be surrounded by the guard ring 5 or other structure to turn the parasitic current back directly to the supply. The foot is not drawn by the internal circuitry. It also requires a suitably low-impedance metal connection to carry a continuous 200mA error current. Therefore, these switches will occupy a considerable area of the stone. In contrast, the first switch 24ca in Figure 3 is isolated from the external input 21c by a resistor 23ca that is typically at least 10 lkohms. In fact, all of the stress will now be absorbed by the input protection diode (not shown) and flow through the resistor 23ca at a current of less than 1 milliamp (mA) into the diffusion of the switch 24a, thus protecting the switch 24ca. The ring only requires minimal special protection. This further reduces the amount of 1C material and cost required. 15 The physical dimensions of these additional resistor banks are typically limited by the matching tolerances obtained from the photo and other steps of the manufacturing process, which are rapidly improved over time when general sizing, however, this is subject to the entity The size of the device of the stress is limited by the maximum current density that can be tolerated in the case of overstress, and there is no significant improvement in the reduction of the process. Therefore, the material of the 1C of the gain controller 22 required to perform the present embodiment 20 continues to decrease as the manufacturing process improves, while the size of the equivalent selection switch in the prior art will remain substantially the same. Another advantage of this embodiment is that the impedance level of the resistors attached to each channel can be independently designed. For example, a channel design can have a high impedance 16 1261414 = to accommodate a relatively high impedance signal source, while another channel, a low impedance level can be improved to improve the signal. And different channels can be no = number or type red. If the "or multiple channels" are connected to a dedicated source of known signal levels, the channel can have a fixed 曰 and /, with two electrical followers 23 and one switch 24. The mouth depends on how many rounds are required, and several selectors 20i-20ii can be connected in parallel as shown. ,

The non-inverting input (+) of the operational amplifier ϋ 25 is typically biased by a good handle-to-handle bias I 1 半 between the positive and negative power supplies of the operational amplifier 25. This maximizes the available peak-to-spike voltage amplitude at the op amp output before over-loading. The negative power supply in this low voltage integrated circuit is grounded under proper conditions, so this bias is half the Vdd/2 of the supply voltage, and Vdd is a positive supply voltage of, for example, 3·3 ν.

If such a single-supply design is used, the voltage at the selected input must also be Vdd/2, and the input signal le is typically a static ground voltage. Therefore, the capacitor 2c shown in Fig. 3 is required to connect this input signal. This DC bias on selected input 21c is then obtained via resistor chain 23c without any additional bias resistors. In a static manner, the voltage across the unselected input 21b via the respective resistor chain 23b or the like is also Vdd/2. Therefore, the capacitor 沘 will be pre-charged, and the capacitor does not need to be charged when the g input is switched from one channel to another. This helps avoid large voltage transients when switching inputs, which can be heard as undesired "waves" and "calls". (Note that the circuit in Figure 1 will require additional switches from unselected channels to Vdd/2, preferably via intermediate resistors (>lkohm) via 17 1261414 to avoid shorting and excessive loading of the input signal source) . Figure 4 shows another embodiment similar to the embodiment of Figure 3, but additionally having means 36 for shorting each impedance chain 33 to a reference voltage. For the sake of clarity, only some of the common elements of Figures 3 and 4 are shown in Figure 4. Figure 4 is a potential problem with the previous embodiment of Figure 3, with the output from the operational amplifier being connected to the unselected input via separate resistor strings. For example, if the resistor string has a total resistance of 60 kohm and the source impedance is 600 〇 11111, then the selected input signal will appear at node 21b and only attenuate 6 〇〇〇/60.6 ohms to 40 dB. If the signal is also used in parallel ramps via 2〇ii (for example, for recording-signals while listening to the other), the crosstalk is unacceptable. 15 20 The typical pressure of the pen pressure is also the reference to the middle of the pre-example and the power supply bias, while maintaining the correct static pressure on the unselected AC connection. The circuit is provided for each unused gain controller and is used for all unused inputs or all gain controls except the selected input-down lean controller (32C). Device. Each short circuit 6C includes a connection 38a-38c to a respective impedance chain 33a-33c, preferably a midpoint of 3^. Switches 37a-37c are connected to respective connections 38a-38c and are turned to * test (4). The short circuit switch's claws are at each short circuit / 36bU_(dGsed), which is connected to the "unselected" booster (32a, 32b). The evaluation of the daily control configuration between the various selectors 20i, 20Π input "channel" 18 1261414 the possibility of crosstalk. If the source/impedance associated with this unused impedance chain 33 is high, then the left end of this input connection or chain η will have a small signal amplitude superimposed thereon. This can be presented at the input of the other selector 20u of the selected source 1 thus causing crosstalk. This short circuit 36 operates to remove the signal superimposed on the unused chain 33 by short circuit to prevent crosstalk. If switch 37b has zero impedance, the output signal of the node bird will be fully suppressed by 70. However, a small switch will typically still have an impedance of, for example, 1 kohm at this node. If this point is along the midpoint of the 60k〇hm string and the source impedance is 600〇hm, then this signal will decay at 381;) by approximately 10 lkohm/30k〇hm = 30dB, and will return to 31b when it reaches 31b Attenuation 600 ohm / 30kohm = 34dB. This is still only a total of 64 commits. A further enhancement of the present embodiment is shown in FIG. 5, which shows the JJ 30 according to FIG. 4, but wherein the short-circuiting device 36 includes a plurality of short-circuiting switches 37i, J7ii, 37iii, which reduces the short-circuit circuits. 36's overall impedance while 15 further reduces crosstalk. For example, if the connections 38i, 38ii, 38iii have taps spaced 15kohm apart, the total attenuation is approximately: (lkohm/15kohm)*(lkohm/15kohm)*(lkohm/15kohm)*(600〇hm/15kohm)=23.5+ 23.5+23.5+28dB=98.5dB, which is the level that can be connected to 20, which can be compared with other unavoidable parasitic coupling effects between device pins or pCB connections. Figure 6 shows another enhanced version of this short circuit 36" which reduces crosstalk. This short circuit switch 37iii, which is closest to the operational amplifier output (V〇), consumes a considerable amount of current. For example, for an output like the above 1Vrms The audio signal 19 1961414 and the 15kohmi air resistance are segments, which will consume 66yArms signal current. If Vr comes; the original impedance is 1〇^, the resulting 66^vrms component will be applied to all Vr Terminals, including other switches and grounds in this and other selector stages. This signal is only 83dB lower than the K1Vrms level. If the signal selected by the selected 5 is applied to the ground of the op amp of the other selector block 20ii, even At 1% gain, this crosstalk signal is doubled (because k positive input-to-output gain = 2 in this structure) produces an unacceptable crosstalk of 774^. This crosstalk is added when more selector blocks are added. It will be even larger. Similar crosstalk can be caused by 10 like chopping of other channel selector blocks appearing on the shorting switch. To allow metal lines on the wafer, it is exemplified by 1μιη觅3 For so Ohm/mm, which is difficult to obtain source impedances less than a few hms without uneconomical over-extended metal. The configuration of Figures 6 and 7 reduces possible crosstalk. Figure 7 shows the supply for Mai Khao The buffer circuit of the private voltage *!*, the output impedance of the open loop (〇pen4ooP) of the op amp 15 with the buffer reference voltage %, is usually reduced to a few tens of ohms by the large negative feedback to the node X. The right-hand short-circuit switch or the short-circuit switch 37iii closest to the operational amplifier 35 in each of the impedance keys % is wired back to the node by a metal connection on the wafer having a private resistance of yy. The other short-circuiting switches and preferably the operational amplifier (35) are connected to ground 20, and are connected back to node X via a separate metal rail (having a resistor represented by resistor XX). These dependencies on the signal current will pass through the short-circuit switch and via separate connection resistors (χχ and yy) which may be tens of ohms to node X%. This resistance will produce considerable voltage ripple, but at node X. The voltage will change to Ai, because its impedance is usually, for example, O.lohm instead of tens of Euros 20 1261414. Depends on: gain selector impedance, crosstalk specification, number of channels, distance from point X to switch, and separate short-circuit switches from separate channel selectors. - The above crosstalk effect is avoided by star-connecting the individual metal rails back to the appropriate point (X). This provides a reference buffer with less than a few ohms of wheel-out impedance without having to surround the wafer because such a line connection requires a very wide metal (a large area will be used). This right-hand side short-circuit switch 37111 carries most of the The current (due to the lVrms at the op amp output) is the current that is connected to the metal line impedance, which is the most common signal crosstalk for the reference section. By connecting the connections back to the decoupling This effect is reduced by the reference buffer output. These other switches can tolerate higher impedance return channels without causing considerable crosstalk by less than a large amount of current. Also, depending on the circuit layout and parasitic mode, It is advantageous to connect the reference voltage terminals of the 15 hand side switch (37bi', etc.) back to the star point X independently. This is to avoid the "leftmost" part of each resistor chain, and the part will be disturbed from an unused one. The channel is input to another person who does not use the channel, such as the second one of the channels in the selector block of ^ not $ · can detect the crosstalk. As discussed above The selector switch, since the % voltage is one-half of the source of the electric 20, so there is no need for the complete c M 〇s pass-through for the short-circuit switch, and - fine MOS (or PMOS, but for the same size, the Radisson 8 typically has A lower resistance is sufficient. The semiconductor switches mentioned in the above description are assumed to be MOSFETs. These components are available in the standard low-cost wide-ranging cm(10) hoarding 21 1261414 bulk circuit technology, which is easy to drive. And a low leakage current is provided. However, other semiconductor devices such as a reinforced JFET or MESFET can be used. A dual carrier transistor can also be used in a similar structure. The selector described above is preferably used in an audio device, for example : High 5 fax amplifiers or stereos in cars for selecting from multiple audio input sources. However, other applications, such as multi-channel precision measurement techniques, may also be considered. The present invention also provides a method of operating a selector, In order to select a specific input source, and to set the appropriate gain factor for that source. 10 By using the input source selected here The source is selected by turning off all of the switches on the gain controller. In addition, the appropriate gain factor is applied by closing the appropriate gate on the gain controller associated with the selected input source. The selected input source. The present invention has been described above with reference to the embodiments, and the modifications and changes thereof are intended to be included in the scope. I: Simple description of the drawings 3 Figure 1 shows the known analog selectors. Structures; Figures 2a-2d show schematic diagrams of CMOS devices, and conductive features for various operational aspects of the device; 20 Figure 3 shows the structure for an analog selector in accordance with an embodiment of the present invention; The structure according to another embodiment; Fig. 5 shows the enhancement of the structure of Fig. 4; Fig. 6 shows another enhancement of the structure of Fig. 5; and Fig. 7 shows the snubber circuit for the reference voltage source. 22 1261414 [The main component representative symbol table of the drawing] la, lb, lc... input source 2a, 2b, 2c... capacitor lOi, 10ii... selector 11a, lib, 11c... input connection 12 , 14...devices 12a, 12b, 12c... input switch 13.. resistor chain 13a...l3n...resistor 14a··. 14η小·.Gain switch 15. Operational amplifier 201 .. Selector 2011.. Selector 21a, 21c.. Node 22b, 22c... Gain Controller 23ba...23kn···Discrete Impedance 23ca...23cn·.·Resistor 24ba·· .24cn · · · · · 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 24 ...impedance chain 33ca, 33ca... impedance 35... operational amplifiers 36b, 36c... short circuit 37a-c... switches 37bi', 37i, 37ii, 37iii... switches 38a-c... 38i, 38ii, 38iii...node D...bungee S...source

Gp ·. · Gate

Gn...gate

Vo...output voltage

Vr... reference voltage

Vtp...critical voltage X...node XX, yy...resistor

twenty three

Claims (1)

4261414 i Pickup, Patent Application Range: Application No. 92126541, Patent Application Revision No. 94〇721. 1· An analog input selector for selecting one of a plurality of analog source devices, including: 5 And an input connection connected to the input source, each of the input connections being connected to each gain control H having at least one zero and one or more non-zero gains, between the input connection and the gain controller Semiconductor switch. 2. If the input of the scope of the scope of the application is the same as the input selection H, each of which includes the connection (4), each of which has a source or a dipole connected to a voltage independent of the input signal. For example, the patent is the analog input selector of item 2, where the voltage unrelated to the input signal is the ground of the selector. 15 such as the input selector of the second patent scope of the patent, further includes an amplifier having an inductive output, and wherein each of the gain controllers further includes an impedance chain connection between the output of the device and the input of each of the inputs The I switch is between the chain and the input of the amplifier. 5. The analog selector of the third application of the patent scope includes an amplifier with 20 inputs and 14 outputs, and each of the gains The controller further includes an impedance chain connection between the output of the amplifier and each of the input connections. The correlation is between the chain and the input of the device. • For example, the input selector of the fourth item of the patent scope is It also includes: when the &Yi Ri inch is used to short-circuit each of the gain controllers to the reference voltage device. 24 ^1414 K Please refer to the fifth round of the patent range, such as the eight-wheel selector, including a is used to short-circuit each of the gain control devices to the reference voltage > • as in the scope of claim 6 or the like, the round-in device, wherein the short circuit; the inclusion includes: the connection between the impedance keys With the reference Between the opening of the 9. = patent application scope category 7 analog input selector clothing. The connection between the ® anti-chain and the reference 'the short-circuit voltage between the opening 10 15 20: the scope of the patent An analog input of the eighth item, wherein the magnified person has a second input connected to the reference electric dust. U: an analog input selector of claim 9 wherein the magnifying jesus has a connection to the reference The second input of the electric dust. 12. The analog input selector of claim 8 wherein the shorting device further comprises - or a plurality of second switches connected between the impedance chain and the reference voltage. An analog input selector as in claim 9 wherein the shorting device further comprises one or more second switches connected between the impedance chain and the reference voltage. The analog input selector, wherein the short circuit 'sets more or eves the second switch' is connected between the impedance key and the reference voltage. 1 5 · 申# patent scope of the first item Input selector, where the short circuit The device further includes one or more second switches connected to the impedance chain and the 25 J261414 Between reference voltages. 16. For example, the analog input selector of the patent scope No. 1, 12, 13, 14 or 15, wherein the switches are] ViOSFET. 17. For example, if the patent application is in the range of 2, 3, 4, 5, 6, 7, 8, 9, 1 , 1 , 12, 13, 14 or 15, the switch is an NMOS. switch. 18. An integrator circuit comprising a selector as in the patent claims 2, 3, 4, 5, 6, 7, 8, 9, 10, u, 12, 13 10 15 20 . Beer 15 or similar wheel 19. An audio equipment 'which includes the integrated circuit of the patent range (4) of the patent application 0 2〇 · an integrated circuit 'which includes the patent scopes 8, 9, 10, u, 12, 13 or 14 or more than the input of one to include, choose. Among them, the short-circuiting device further includes the third switch which is independent of the voltage of the short-circuiting device switch. 21·—A kind of audio equipment, including, for example, Shen Yilu. ^ Patent scope of the 2nd item of the integrated body sobbing as in the application of the scope of the 18th element of the integrated circuit, M0SFET. The temple switch is closed as 23. MOSFET as the second item of the patent application scope. /, Zhong 6 Hai and so on 24 · If the scope of the application for the scope of the 18th is the month, and the road, which is the stem P bow NM0S switch. τ is the temple open 26 ς / (Ι 2614ί14 \ 25. Such as the application of the scope of the 20th integrated circuit, wherein the switch is an NMOS switch. 26. A method of operating the selector, this selector includes for connecting at most Multiple input connections of input sources, each of which is connected to an individual gain controller having 5 at least one zero and one or more non-zero gains, the method comprising the steps of: An input source is selected by providing the individual gain controller with a non-zero gain and by providing other gain controllers each having a zero gain. 27