Analog control circuit for operational amplifier input signal selection
The analog control circuit with a comparator module and current mirrors addresses the limitations of traditional analog switches by seamlessly switching input pairs in operational amplifiers, reducing on-resistance and noise, and ensuring high precision and low power consumption for fast responses.
Patent Information
- Application Number
- CN202411293018.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-31
AI Technical Summary
Traditional analog switch-based input signal selection in operational amplifiers introduces on-resistance, increases system complexity and cost, requires a bias current, and introduces noise and switching delay, making it unsuitable for high precision, low power consumption, and fast response applications.
An analog control circuit using a comparator module with current mirrors to switch input pairs of transistors in operational amplifiers, mirroring current between branches to achieve seamless signal switching without the need for analog switches.
The solution reduces on-resistance, complexity, and noise, while maintaining high precision and low power consumption, enabling fast response times in operational amplifiers.
Smart Images
Figure CN119232093A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of analog circuit design, and in particular to an analog control circuit for selecting an input signal of an operational amplifier. Background Art
[0002] In analog electronic circuit design, operational amplifiers are extremely common components and are widely used in signal processing, filtering, amplification and other occasions. In traditional circuit design, the selection of different input signals is usually achieved by using logic-controlled analog switches. However, on the one hand, the analog switch will introduce on-resistance and require a very small bias current at the input of the operational amplifier. In order to reduce the on-resistance, the area of the analog switch is usually increased, which increases the complexity and cost of the system. On the other hand, since the analog switch itself requires an additional drive circuit, it will introduce additional noise and greater switching delay. Therefore, the traditional method of using analog switches is not suitable for application scenarios that require high precision, low power consumption and fast response. Summary of the invention
[0003] In order to solve the above problems, the present application provides an analog control circuit for selecting an input signal of an operational amplifier.
[0004] The embodiment of the present application provides an analog control circuit for selecting an input signal of an operational amplifier, comprising a comparator module connected between a positive power supply and a negative power supply and an input pair tube group of the operational amplifier, wherein: The comparator module comprises a first branch having a first signal input thereto and a second branch having a second signal input thereto, and the comparator module is used to compare the first signal and the second signal to control the on / off of the first branch and the on / off of the second branch; The input pair tube group includes a first input pair tube and a second input pair tube; A first current mirror is provided between the first branch and the first input pair of tubes, and the first current mirror is used to mirror the current of the first branch to the branch where the first input pair of tubes is located when the first branch is turned on and the second branch is turned off, so that the first input pair of tubes serves as the input pair of tubes of the operational amplifier; A second current mirror is arranged between the second branch and the second input pair of tubes. The second current mirror is used to mirror the current of the second branch to the branch where the second input pair of tubes is located when the second branch is turned on and the first branch is turned off, so that the second input pair of tubes serves as the input pair of tubes of the operational amplifier.
[0005] In some embodiments, the first branch includes a first input transistor and the second branch includes a second input transistor; The comparator module further comprises a first current source, wherein a positive electrode of the first current source is connected to the positive power supply, and a negative electrode of the first current source is connected to an emitter of the first input transistor and an emitter of the second input transistor respectively; The base of the first input transistor is used to input the first signal, the base of the second input transistor is used to input the second signal, and the first input transistor and the second input transistor constitute an input pair of transistors of the comparator; The collector of the first input transistor is used to provide a reference current for the first current mirror, and the collector of the second input transistor is used to provide a reference current for the second current mirror.
[0006] In some embodiments, the first current mirror includes a first mirror transistor and a first tail current transistor; The base of the first mirror transistor is short-circuited to the collector, the emitter is grounded, and the collector is connected to the collector of the first input transistor; The emitter of the first tail current transistor is grounded, the collector is connected to the branch where the first input pair of transistors is located, and provides tail current for the first input pair of transistors, and the base of the first tail current transistor is connected to the collector of the first input transistor; The second current mirror includes a second mirror transistor and a second tail current transistor; The base of the second mirror transistor is short-circuited to the collector, the emitter is grounded, and the collector is connected to the collector of the second input transistor; The emitter of the second tail current transistor is grounded, the collector is connected to the branch where the second input pair transistor is located, and the base of the second tail current transistor is connected to the collector of the second input transistor.
[0007] In some embodiments, the first input pair of tubes and the second input pair of tubes share a positive phase input tube, the first input pair of tubes further includes a first negative phase input tube, and the second input pair of tubes further includes a second negative phase input tube; The base of the first negative phase input tube is used to receive a first negative phase input signal of the operational amplifier, the base of the second negative phase input tube is used to receive a second negative phase input signal of the operational amplifier, and the base of the positive phase input tube is used to receive a positive phase input signal of the operational amplifier; After the collectors of the first negative phase input tube and the second negative phase input tube are connected in parallel, they are connected to the positive power supply through a first load resistor, and the collector of the positive phase input tube is connected to the positive power supply through a second load resistor; The emitter of the first negative phase input tube and the emitter of the positive phase input tube are connected in parallel and then connected to the collector of the first tail current transistor; The emitter of the second negative phase input tube and the emitter of the positive phase input tube are connected in parallel and then connected to the collector of the second tail current transistor.
[0008] In some embodiments, the comparator module further includes a third branch, the third branch includes a third input transistor, and a base of the third input transistor is connected to a bias voltage supply unit; The input pair tube group further includes a third input pair tube, the third input pair tube includes the positive phase input tube and a third negative phase input tube, and the base of the third negative phase input tube is connected to the output end of the operational amplifier; A third current mirror is connected between the third branch and the branch where the third input pair of tubes are located; The comparator module is also used to compare the first signal and the second signal to control the on and off of the third branch. The third current mirror is used to mirror the current of the third branch to the branch where the third input pair tube is located when the first branch and the second branch are cut off and the third branch is turned on.
[0009] In some embodiments, the third current mirror includes a third mirror transistor and a third tail current transistor; The base of the third mirror transistor is short-circuited to the collector, the emitter is grounded, and the collector is connected to the collector of the third input transistor; The emitter of the third tail current transistor is grounded, the collector is connected to the parallel node of the emitters of the positive phase input tube and the third negative phase input tube, and the base of the third tail current transistor is connected to the collector of the third input transistor.
[0010] In some embodiments, it further includes a first protection transistor and a second protection transistor, wherein the drain of the first protection transistor is connected to the emitter of the first input transistor, and the base and the collector are respectively connected to the negative electrode of the first current source; The drain of the second protection transistor is connected to the emitter of the second input transistor, and the base and collector are respectively connected to the negative electrode of the first current source.
[0011] In some embodiments, a current discharge module is further included, and the current discharge module is used to discharge the current in the first branch and the second branch when the first branch and the second branch are turned on at the same time.
[0012] In some embodiments, the current discharge module includes a first MOS transistor, a second MOS transistor, a first transition transistor with a base and a collector short-circuited, and a second transition transistor with a base and a collector short-circuited; The base of the first transition transistor is connected to the collector of the first input transistor, and the emitter is connected to the collector of the first mirror transistor; The base of the second transition transistor is connected to the collector of the second input transistor, and the emitter is connected to the collector of the second mirror transistor; The gate of the first MOS transistor is connected to the base of the second transition transistor, the source is connected to the negative power supply, and the drain is connected to the emitter of the first transition transistor; The gate of the second MOS transistor is connected to the base of the first transition transistor, the source is connected to the negative power supply, and the drain is connected to the emitter of the second transition transistor.
[0013] In some embodiments, the discharge module further includes a third MOS tube and a fourth MOS tube for discharging the current in the third branch; The gate of the third MOS transistor is connected to the base of the first transition transistor, the source is connected to the negative power supply, the drain is connected in parallel with the drain of the fourth MOS transistor, and then connected to the collector of the third input transistor; The gate of the fourth MOS transistor is connected to the base of the second transition transistor, and the source is connected to the negative power supply.
[0014] The technical solution of this application has at least the following advantages: By setting a comparator module including a first branch and a second branch, and mirroring the current in the first branch to the branch where the first input pair of tubes of the operational amplifier is located through a first current mirror, and mirroring the current in the second branch to the branch where the second input pair of tubes of the operational amplifier is located through a second current mirror, the first current mirror is used to mirror the current in the first branch to the branch where the first input pair of tubes is located when the first branch is turned on and the second branch is turned off, so that the first input pair of tubes serves as the input pair of tubes of the operational amplifier, and the second current mirror is used to mirror the current in the second branch to the branch where the second input pair of tubes is located when the second branch is turned on and the first branch is turned off, so that the second input pair of tubes serves as the input pair of tubes of the operational amplifier, thereby realizing the switching of the input pair of tubes of the operational amplifier by using the comparator module, that is, realizing the switching of the signal in the input stage of the operational amplifier. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0016] Figure 1 is a circuit diagram of an analog control circuit for selecting an operational amplifier input signal provided by an exemplary embodiment of the present application; Figure 2 It is a circuit diagram of another analog control circuit for selecting an operational amplifier input signal provided by an exemplary embodiment of the present application.
[0017] L1, first branch; L2, second branch; L3, third branch; G1, input pair pipe group. DETAILED DESCRIPTION
[0018] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0019] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0020] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0021] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0022] The present application provides an analog control circuit for selecting an input signal of an operational amplifier, which includes a comparator module connected between a positive power supply VCC and a negative power supply VEE, and an input pair transistor group G1 of the operational amplifier. The analog control circuit for selecting an input signal of the operational amplifier provided by the embodiments of the present application can be applicable to a variety of common logic levels, such as 1.2V, 1.8V, 3V, 5V, etc., and the value ranges of the positive power supply VCC and the negative voltage VEE are flexible. For example, when the logic level is 3.3V, the lower limit of the voltage of the positive voltage VCC satisfies VCC > 3.3V + 2VBE, and the upper limit depends on the device breakdown voltage. At the same time, the upper limit of the voltage of the negative power supply VEE satisfies V33 < GND - 2VBE, and the lower limit does not exceed the device breakdown voltage. Wherein, VBE is the voltage difference between the base and the emitter of a transistor. Taking a silicon transistor as an example, VBE is usually 0.6~0.7V at room temperature, and the specific value is subject to the actual use.
[0023] Wherein, referring to Figure 1 , the comparator module includes a first branch L1 input with a first signal YP and a second branch L2 input with a second signal YN, and the comparator module is used to compare the magnitudes of the first signal YP and the second signal YN, so as to control the on-off of the first branch L1 and the on-off of the second branch L2.
[0024] The input pair transistor group G1 includes a first input pair transistor and a second input pair transistor, and a first current mirror is arranged between the first branch L1 and the first input pair transistor. The first current mirror is used to mirror the current in the first branch L1 to the branch where the first input pair transistor is located when the first branch L1 is conducting and the second branch L2 is turned off, so that the first input pair transistor serves as the input pair transistor of the operational amplifier. At the same time, a second current mirror is arranged between the second branch L2 and the second input pair transistor. The second current mirror is used to mirror the current in the second branch L2 to the branch where the second input pair transistor is located when the second branch L2 is conducting and the first branch L1 is turned off, so that the second input pair transistor serves as the input pair transistor of the operational amplifier. By adopting the above technical solutions, the switching of the input pair transistors of the operational amplifier can be realized by using the comparator module, that is, the switching of the signals in the input stage of the operational amplifier is realized.
[0025] Further, referring to Figure 1In this embodiment, the first branch L1 includes a first input transistor Q1, and the second branch L2 includes a second input transistor Q2, and the first input transistor Q1 and the second input transistor Q2 are both PNP transistors. The comparator module also includes a first current source I1, the positive electrode of the first current source I1 is connected to the positive power supply VCC, and the negative electrode is respectively connected to the emitter of the first input transistor Q1 and the emitter of the second input transistor Q2, and is used to provide a tail current source for the first input transistor Q1 and the second input transistor Q2. The base of Q1 is used to input the first signal YP, and the base of Q2 is used to input the second signal YN. The first input transistor Q1 and the second input transistor Q2 constitute an input pair of comparators. The collector of the first input transistor Q1 is used to provide a reference current for the first current mirror I1, and the collector of the second input transistor Q2 is used to provide a reference current for the second current mirror I2.
[0026] Reference Figure 1 The first current mirror includes a first mirror transistor Q9 and a first tail current transistor Q12, and both the first mirror transistor Q9 and the first tail current transistor Q12 are NPN transistors. The base of the first mirror transistor Q9 is short-circuited to the collector through a resistor R7, the emitter is grounded through a resistor R2, and the collector is connected to the collector of the first input transistor Q1. The emitter of the first tail current transistor Q12 is grounded through a resistor R5, the collector is connected to the branch where the first input pair of transistors is located, and the tail current is provided to the first input pair of transistors. The base of the first tail current transistor Q12 is connected to the collector of the first input transistor Q1, so that the current in the first branch L1 is mirrored to the collector of the first tail current transistor Q12, and then provided to the branch where the first input pair of transistors is located.
[0027] Reference Figure 1 The second current mirror includes a second mirror transistor Q10 and a second tail current transistor Q11, and the second mirror transistor Q10 and the second tail current transistor Q11 are both NPN transistors. The base of the second mirror transistor Q10 is short-circuited to the collector through a resistor R8, the emitter is grounded through a resistor R3, and the collector is connected to the collector of the second input transistor Q2. The emitter of the second tail current transistor Q11 is grounded through a resistor R4, the collector is connected to the branch where the second input pair of transistors is located, and the tail current is provided to the second input pair of transistors. The base of the second tail current transistor Q11 is connected to the collector of the second input transistor Q2, so that the current in the second branch L2 is mirrored to the collector of the second tail current transistor Q11, and then provided to the branch where the second input pair of transistors is located.
[0028] Further, refer to Figure 1In this embodiment, the first input pair of tubes and the second input pair of tubes share a positive phase input tube Q7, the first input pair of tubes also includes a first negative phase input tube Q4, and the second input pair of tubes also includes a second negative phase input tube Q5, wherein the positive phase input tube Q7, the first negative phase input tube Q4 and the second negative phase input tube Q5 are all NPN type transistors.
[0029] The base of the first negative phase input tube Q4 is used to receive the first negative phase input signal V1 of the operational amplifier, the base of the second negative phase input tube Q5 is used to receive the second negative phase input signal V2 of the operational amplifier, and the positive phase input tube Q7 is used to receive the positive phase input signal VP of the operational amplifier.
[0030] After the collectors of the first negative phase input tube Q4 and the second negative phase input tube Q5 are connected in parallel, they are connected to the positive power supply VCC through the first load resistor R15, and the collector of the positive phase input tube Q7 is connected to the positive power supply VCC through the second load resistor R6. The emitter of the first negative phase input tube Q4 is connected in series with a resistor R11, the emitter of the second negative phase input tube Q5 is connected in parallel with a resistor R9, the emitter of the positive phase input tube Q7 is connected in parallel with a resistor R12 and a resistor R10, the other end of the resistor R11 and the other end of the resistor R12 are connected in parallel to the collector of the first tail current transistor Q12, and the other end of the resistor R9 and the other end of the resistor R10 are connected in parallel to the collector of the second tail current transistor Q11. Thus, the connection between the first current mirror and the branch where the first input pair of tubes are located, and the connection between the second current mirror and the branch where the second input pair of tubes are located are realized.
[0031] Further, see Figure 2 In some embodiments, in order to realize the high impedance state of the operational amplifier, the comparator module further includes a third branch L3, the third branch L3 includes a third input transistor Q3, the base of the third input transistor Q3 is connected to a bias voltage supply unit, and is used to provide a bias voltage VB for the third input transistor Q3. The input pair tube group G1 also includes a third input pair tube, the third input pair tube includes a positive phase input tube Q7 and an NPN type third negative phase input tube Q6, the input signal VN of the base of the third negative phase input tube Q6 is connected to the output end of the operational amplifier, and the collector is connected to the positive power supply VCC through the load resistor R15 after being connected in parallel with the collectors of the first negative phase input tube Q4 and the second negative phase input tube Q5.
[0032] A third current mirror is connected between the third branch L3 and the branch where the third input pair of transistors is located. At this time, the comparator module is also used to compare the first signal YP and the second signal YN to control the on and off of the third branch L3. The third current mirror is used to mirror the current of the third branch L3 to the branch where the third input pair of transistors is located when the first branch L1 and the second branch L2 are cut off and the third branch L3 is turned on, so that the third input pair of transistors serves as the input pair of transistors of the operational amplifier.
[0033] Furthermore, in the above circuit, the third input transistor Q3 is a PNP transistor, whose emitter is connected in parallel with the emitters of the first input transistor Q1 and the second input transistor Q3, and then connected to the negative electrode of the first current source I1, and the collector is used to provide a reference current for the third current mirror.
[0034] The bias voltage supply unit may include a second current source I2 and a diode-connected bipolar junction transistor in series, wherein each bipolar junction transistor may provide a voltage drop of 0.6V to 0.7V, and the number of bipolar junction transistors may be adjusted according to the size of the logic level, so that the bias voltage VB provided to the third input transistor Q3 is an intermediate value between a logic high level and a logic low level. In some embodiments, the bias voltage supply unit may include a series resistor in addition to the second current source I2 and the diode-connected bipolar junction transistor in series, so as to achieve accurate adjustment of the bias voltage VB.
[0035] In the embodiment of the present application, taking the logic level of 3.3V as an example, Figure 2 As shown, the bias voltage supply unit includes a second current source I2 and bipolar junction transistors Q18 and Q19 connected in series, both of which are NPN transistors with bases and collectors shorted, the collector of the bipolar junction transistor Q18 is grounded, the emitter is connected to the emitter of the bipolar junction transistor Q19, the collector of the bipolar junction transistor Q19 is connected to the negative electrode of the second current source I2, and the positive electrode of the second current source I2 is connected to the positive power supply VCC. The base of the third input transistor Q3 is connected between the negative electrode of the positive power supply VCC and the collector of the bipolar junction transistor Q19 to obtain the bias voltage VB.
[0036] Further, see Figure 2 The third current mirror includes a third mirror transistor Q8 and a third tail current transistor Q13. The base of the third mirror transistor Q8 is short-circuited to the collector, the emitter is grounded through a resistor R1, and the collector is connected to the collector of the third input transistor Q3. The emitter of the third tail current transistor Q13 is grounded through a resistor R6. The emitter of the third negative phase input tube Q6 is connected to a resistor R13, and the resistor R13 and the resistor R14 connected to the emitter of the positive phase input tube Q7 are connected in parallel to the collector of the third tail current transistor Q13. The base of the third tail current transistor Q13 is connected to the collector of the third input transistor Q3.
[0037] Furthermore, in order to reduce the overvoltage of some components in the circuit, the comparator module is also configured with a first protection transistor Q16 and a second protection transistor Q17. Figure 2The drain of the first protection transistor Q16 is connected to the emitter of the first input transistor Q1, and the base and collector are respectively connected to the negative electrode of the first current source I1. The drain of the second protection transistor Q17 is connected to the emitter of the second input transistor Q2, and the base and collector are respectively connected to the negative electrode of the first current source I1.
[0038] In the above circuit, when the input first signal YP is less than the second signal YN, the first input transistor Q1 is turned on, and the second input transistor Q2 and the third input transistor Q3 are turned off. At this time, the current of the first current source I1 flows entirely to the first branch L1, and is mirrored to the branch where the first tail current transistor Q12 is located through the first current mirror. At this time, the input pair of tubes of the operational amplifier is the first negative phase input tube Q4 and the positive phase input tube Q7, thereby realizing the input of the first negative phase input signal V1.
[0039] When the input first signal YP is greater than the second signal YN, the second input transistor Q2 is turned on, while the first input transistor Q1 and the third input transistor Q3 are turned off. At this time, the current of the first current source I1 flows entirely to the second branch L2, and is mirrored to the branch where the second tail current transistor Q11 is located through the second current mirror. At this time, the input pair of tubes of the operational amplifier is the second negative phase input tube Q5 and the positive phase input tube Q7, thereby realizing the input of the second negative phase input signal V2.
[0040] When the first signal YP and the second signal YN input to the comparator module are both at a high level, that is, YP=YN=1, the first input transistor Q1 and the second input transistor Q2 are turned off, and the third input transistor Q3 is turned on. At this time, the current of the first current source I1 flows entirely into the third branch L3, and is mirrored by the third current mirror to the branch where the third tail current transistor Q13 is located. At this time, the input pair of tubes of the operational amplifier is the positive phase input tube Q7 and the third negative phase input tube Q6. Since the input signal VN of the base of the third negative phase input tube Q6 is connected to the output end of the operational amplifier, the connection between the operational amplifier and other circuit loops is cut off, so that the entire operational amplifier acts as a unit gain buffer, and the positive phase input signal VP of the operational amplifier is locked in the current state, realizing the high impedance state of the operational amplifier.
[0041] Furthermore, in order to facilitate the discharge of current, the analog control circuit for selecting the operational amplifier input signal may also include a current discharge module, which is used to discharge the current in the first branch L1 and the second branch L2 when the first branch L1 and the second branch L2 are turned on at the same time. In addition, when the third branch L3 exists, the current discharge module is also used to discharge the current in the third branch L3 at the same time.
[0042] Reference Figure 2The current discharge module includes a first MOS tube M1, a second MOS tube M2, a first transition transistor Q14 with a base and a collector short-circuited, and a second transition transistor Q15 with a base and a collector short-circuited. Among them, the base of the first transition transistor Q14 is connected to the collector of the first input transistor Q1, and the emitter is connected to the collector of the first mirror transistor Q9. The base of the second transition transistor Q15 is connected to the collector of the second input transistor Q2, and the emitter is connected to the collector of the second mirror transistor Q10. The gate of the first MOS tube M1 is connected to the base of the second transition transistor Q15, the source is connected to the negative power supply VEE, and the drain is connected to the emitter of the first transition transistor Q14. The gate of the second MOS tube M2 is connected to the base of the first transition transistor Q14, the source is connected to the negative power supply VEE, and the drain is connected to the emitter of the second transition transistor Q15.
[0043] Furthermore, the current discharge module also includes a third MOS tube M3 and a fourth MOS tube M4, wherein the gate of the third MOS tube M3 is connected to the base of the first transition transistor Q14, the source is connected to the negative power supply VEE, and the drain is connected in parallel with the drain of the fourth MOS tube M4 and then connected to the collector of the third input transistor Q3. The gate of the fourth MOS tube M4 is connected to the base of the second transition transistor Q15, and the source is connected to the negative power supply VEE.
[0044] When the first signal YP and the second signal YN input to the comparator module are both at low level, that is, YP=YN=0, the first input transistor Q1 and the second input transistor Q2 divide the current of the first current source I1 equally, the third input transistor Q3 is turned off, and at the same time, the first mirror transistor Q9 and the second mirror transistor Q10 are turned off, and the first MOS transistor M1 and the second MOS transistor M2 bear the current of the first branch L1 and the second branch L2 respectively, thereby realizing the discharge of the current in the first branch L1 and the second branch L2, and at the same time, the third MOS transistor M3 and the fourth MOS transistor M4 also discharge the current in the third branch L3. Since there is no current on the first mirror transistor Q9, the second mirror transistor Q10 and the third mirror transistor Q8, there is no current in the first tail current transistor Q12, the second tail current transistor Q11 and the third tail current transistor Q13, thereby realizing the low leakage state of the operational amplifier.
[0045] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.
Claims
1. An analog control circuit for selecting an input signal of an operational amplifier, characterized in that: The invention comprises a comparator module connected between a positive power supply and a negative power supply and an input pair tube group of an operational amplifier, wherein: The comparator module comprises a first branch having a first signal input thereto and a second branch having a second signal input thereto, and the comparator module is used to compare the first signal and the second signal to control the on / off of the first branch and the on / off of the second branch; The input pair tube group includes a first input pair tube and a second input pair tube; A first current mirror is provided between the first branch and the first input pair of tubes, and the first current mirror is used to mirror the current of the first branch to the branch where the first input pair of tubes is located when the first branch is turned on and the second branch is turned off, so that the first input pair of tubes serves as the input pair of tubes of the operational amplifier; A second current mirror is arranged between the second branch and the second input pair of tubes. The second current mirror is used to mirror the current of the second branch to the branch where the second input pair of tubes is located when the second branch is turned on and the first branch is turned off, so that the second input pair of tubes serves as the input pair of tubes of the operational amplifier.
2. The analog control circuit for selecting an operational amplifier input signal according to claim 1, characterized in that: The first branch includes a first input transistor, and the second branch includes a second input transistor; The comparator module further comprises a first current source, wherein a positive electrode of the first current source is connected to the positive power supply, and a negative electrode of the first current source is connected to an emitter of the first input transistor and an emitter of the second input transistor respectively; The base of the first input transistor is used to input the first signal, the base of the second input transistor is used to input the second signal, and the first input transistor and the second input transistor constitute an input pair of transistors of the comparator; The collector of the first input transistor is used to provide a reference current for the first current mirror, and the collector of the second input transistor is used to provide a reference current for the second current mirror.
3. The analog control circuit for selecting an operational amplifier input signal according to claim 2, characterized in that: The first current mirror comprises a first mirror transistor and a first tail current transistor; The base of the first mirror transistor is short-circuited to the collector, the emitter is grounded, and the collector is connected to the collector of the first input transistor; The emitter of the first tail current transistor is grounded, the collector is connected to the branch where the first input pair of transistors is located, and provides tail current for the first input pair of transistors, and the base of the first tail current transistor is connected to the collector of the first input transistor; The second current mirror includes a second mirror transistor and a second tail current transistor; The base of the second mirror transistor is short-circuited to the collector, the emitter is grounded, and the collector is connected to the collector of the second input transistor; The emitter of the second tail current transistor is grounded, the collector is connected to the branch where the second input pair transistor is located, and the base of the second tail current transistor is connected to the collector of the second input transistor.
4. The analog control circuit for selecting an operational amplifier input signal according to claim 3, characterized in that: The first input pair of tubes and the second input pair of tubes share a positive phase input tube, the first input pair of tubes further includes a first negative phase input tube, and the second input pair of tubes further includes a second negative phase input tube; The base of the first negative phase input tube is used to receive a first negative phase input signal of the operational amplifier, the base of the second negative phase input tube is used to receive a second negative phase input signal of the operational amplifier, and the base of the positive phase input tube is used to receive a positive phase input signal of the operational amplifier; After the collectors of the first negative phase input tube and the second negative phase input tube are connected in parallel, they are connected to the positive power supply through a first load resistor, and the collector of the positive phase input tube is connected to the positive power supply through a second load resistor; The emitter of the first negative phase input tube and the emitter of the positive phase input tube are connected in parallel and then connected to the collector of the first tail current transistor; The emitter of the second negative phase input tube and the emitter of the positive phase input tube are connected in parallel and then connected to the collector of the second tail current transistor.
5. The analog control circuit for selecting an operational amplifier input signal according to claim 4, characterized in that: The comparator module further includes a third branch, the third branch includes a third input transistor, and the base of the third input transistor is connected to a bias voltage supply unit; The input pair tube group further includes a third input pair tube, the third input pair tube includes the positive phase input tube and a third negative phase input tube, and the base of the third negative phase input tube is connected to the output end of the operational amplifier; A third current mirror is connected between the third branch and the branch where the third input pair of tubes are located; The comparator module is also used to compare the first signal and the second signal to control the on and off of the third branch. The third current mirror is used to mirror the current of the third branch to the branch where the third input pair tube is located when the first branch and the second branch are cut off and the third branch is turned on.
6. The analog control circuit for selecting an operational amplifier input signal according to claim 5, characterized in that: The third current mirror comprises a third mirror transistor and a third tail current transistor; The base of the third mirror transistor is short-circuited to the collector, the emitter is grounded, and the collector is connected to the collector of the third input transistor; The emitter of the third tail current transistor is grounded, the collector is connected to the parallel node of the emitters of the positive phase input tube and the third negative phase input tube, and the base of the third tail current transistor is connected to the collector of the third input transistor.
7. The analog control circuit for selecting an operational amplifier input signal according to claim 2, characterized in that: It also includes a first protection transistor and a second protection transistor, wherein the drain of the first protection transistor is connected to the emitter of the first input transistor, and the base and the collector are respectively connected to the negative electrode of the first current source; The drain of the second protection transistor is connected to the emitter of the second input transistor, and the base and collector are respectively connected to the negative electrode of the first current source.
8. The analog control circuit for selecting an operational amplifier input signal according to any one of claims 1 to 7, characterized in that: It also includes a current discharge module, which is used to discharge the current in the first branch and the second branch when the first branch and the second branch are turned on at the same time.
9. The analog control circuit for selecting an operational amplifier input signal according to claim 8, characterized in that: The current discharge module includes a first MOS tube, a second MOS tube, a first transition transistor with a base and a collector short-circuited, and a second transition transistor with a base and a collector short-circuited; The base of the first transition transistor is connected to the collector of the first input transistor, and the emitter is connected to the collector of the first mirror transistor; The base of the second transition transistor is connected to the collector of the second input transistor, and the emitter is connected to the collector of the second mirror transistor; The gate of the first MOS transistor is connected to the base of the second transition transistor, the source is connected to the negative power supply, and the drain is connected to the emitter of the first transition transistor; The gate of the second MOS transistor is connected to the base of the first transition transistor, the source is connected to the negative power supply, and the drain is connected to the emitter of the second transition transistor.
10. The analog control circuit for selecting an operational amplifier input signal according to claim 9, characterized in that: The discharge module further includes a third MOS tube and a fourth MOS tube for discharging the current in the third branch; The gate of the third MOS transistor is connected to the base of the first transition transistor, the source is connected to the negative power supply, the drain is connected in parallel with the drain of the fourth MOS transistor, and then connected to the collector of the third input transistor; The gate of the fourth MOS transistor is connected to the base of the second transition transistor, and the source is connected to the negative power supply.