CN-122026821-A - Operational amplifier with base current eliminating structure

CN122026821ACN 122026821 ACN122026821 ACN 122026821ACN-122026821-A

Abstract

The invention provides an operational amplifier with a base current eliminating structure, which comprises an input stage, wherein the input stage is connected with an input common mode voltage through an input pair, the base electrode of the input pair is connected with the base current eliminating structure, the emitter electrode of the input pair is connected with negative power supply voltage through a bias branch, the collector electrode of the input pair is connected with a common mode feedback circuit, and the common mode feedback circuit is used for providing bias for the base current eliminating structure so as to eliminate the base current of the input pair through the base current eliminating structure. The invention solves the problem that the base current of the operational amplifier is too high under the bipolar technology, and large noise is generated under the condition of large internal resistance of the signal source.

Inventors

CUI DAJIAN
XI SHUIQING
JIA BOYI
LIU JIAYANG
GAO RUOYAO
Zhou Aishi
REN LI

Assignees

中国电子科技集团公司第四十四研究所

Dates

Publication Date: 20260512
Application Date: 20260203

Claims (10)

1. An operational amplifier with a base current cancellation structure, wherein the operational amplifier comprises an input stage, wherein the input stage is connected with an input common mode voltage through an input pair, the base of the input pair is connected with the base current cancellation structure, the emitter of the input pair is connected with a negative supply voltage through a bias branch, the collector of the input pair is connected with a common mode feedback circuit, and the common mode feedback circuit is used for providing bias for the base current cancellation structure so as to cancel the base current of the input pair through the base current cancellation structure.
2. The operational amplifier with the base current elimination structure according to claim 1, wherein the input pair tube comprises a zeroth NPN tube and a first NPN tube, bases of the zeroth NPN tube and the first NPN tube are connected with the input common mode voltage, a source electrode of the zeroth NPN tube is connected with a source electrode of the first NPN and is connected with the bias branch in parallel, and a drain electrode of the zeroth NPN tube and a drain electrode of the first NPN tube are respectively connected with the common mode feedback circuit.
3. The operational amplifier with a base current elimination structure according to claim 1 or 2, wherein the bias branch includes a ninth NPN transistor and a first resistor, a base of the ninth NPN transistor is connected to a negative bias voltage, a collector of the ninth NPN transistor is connected to an emitter of the input pair transistor, and an emitter of the ninth NPN transistor is connected to a negative supply voltage through the first resistor.
4. The operational amplifier with the base current elimination structure according to claim 3, wherein the base current elimination structure comprises a fourth PNP tube, a fifth PNP tube, a sixth PNP tube, a tenth PNP tube, an eleventh NPN tube, a twelfth PNP tube, a thirteenth NPN tube and a fourteenth PNP tube, wherein a collector of the fourth PNP tube is connected with a base of the zeroth NPN tube, the base is connected with a base of the fifth PNP tube, a collector of the fifth PNP tube is connected with a base of the first NPN tube, an emitter of the fourth PNP tube, the fifth PNP tube and an emitter of the sixth PNP tube are connected with each other and connected with a base of the thirteenth NPN tube, a base of the sixth PNP tube is connected with a collector of the eleventh NPN tube, a base of the eleventh NPN tube is connected with a negative bias voltage, an emitter of the eleventh NPN tube is connected with a negative power supply voltage through a fifth resistor, a collector of the twelfth PNP tube is connected with a collector of the thirteenth NPN tube is connected with a positive power supply voltage, and a negative power supply voltage is connected with a collector of the thirteenth power supply through a positive power supply.
5. The operational amplifier with a base current elimination structure according to claim 4, wherein the common mode feedback circuit includes a seventh PNP transistor, an eighth PNP transistor, a second PNP transistor, a third PNP transistor, a fifteenth PNP transistor, a sixteenth PNP transistor, a seventeenth NPN transistor, an eighteenth NPN transistor, a nineteenth NPN transistor, a twenty-first NPN transistor, a first capacitor, a second capacitor, a third capacitor, a second resistor, a third resistor, a fourth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, and a twelfth resistor; The base of the seventh PNP tube is connected with the base of the eighth PNP tube and is connected with the base of the twelfth PNP tube, one end of the ninth resistor and one end of the tenth resistor in parallel, the collector of the seventh PNP tube is connected with the collector of the eighth NPN tube, the collector of the eighth PNP tube is connected with the collector of the first NPN tube, the emitter of the seventh PNP tube is connected with the positive power supply voltage through the second resistor, the emitter of the eighth PNP tube is connected with the positive power supply voltage through the third resistor, the base of the second PNP tube is connected with the collector of the seventh PNP tube and is connected with the test end through the first capacitor, the emitter of the second PNP tube is connected with the collector of the fifteenth PNP tube and is connected with the base of the seventh NPN tube through the ninth resistor, the base of the eighth PNP tube is connected with the collector of the eighth NPN tube through the second capacitor and is connected with the positive power supply voltage through the second capacitor, the emitter of the sixteenth PNP tube and the sixteenth PNP tube is connected with the positive power supply voltage through the sixteenth resistor and the emitter of the sixteenth PNP tube, the base of the sixteenth PNP tube is connected with the positive power supply voltage through the sixteenth resistor and the base of the sixteenth resistor is connected with the positive power supply voltage through the sixteenth resistor respectively, the emitter of the seventeenth NPN tube is respectively connected with the collector and the base of the eighteenth NPN tube, the emitter of the eighteenth NPN tube is respectively connected with the base of the nineteenth NPN tube and the collector of the twenty-first NPN tube, the base of the twenty-first NPN tube is respectively connected with the emitter of the nineteenth NPN tube and the base of the twenty-first NPN tube, the emitter of the twenty-first NPN tube is connected with the negative power supply voltage through the third capacitor and the eleventh resistor which are connected in parallel, the emitter of the twenty-first NPN tube is connected with the negative power supply voltage through the twelfth resistor, and the collectors of the nineteenth NPN tube and the third PNP tube are interconnected to serve as the output end of the input stage.
6. The operational amplifier with base current cancellation structure according to claim 5, further comprising an output stage that generates an output of the operational amplifier based on an output terminal voltage of the input stage and a reference current.
7. The operational amplifier with a base current elimination structure according to claim 6, wherein the output stage comprises a twenty-second NPN tube, a twenty-third NPN tube, a twenty-fourth PNP tube, a twenty-fifth PNP tube, a twenty-sixteen PNP tube, a twenty-seventeenth PNP tube, a twenty-eighth PNP tube, a twenty-ninth PNP tube, a thirty-ninth NPN tube, a thirty-eleventh NPN tube, a thirty-second NPN tube, a thirty-thirteenth NPN tube, a thirty-fourth PNP tube, a thirty-fifth NPN tube, a thirty-sixteen PNP tube, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor, and a twenty-third resistor; The collector of the twenty-second NPN tube is respectively connected with the base of the twenty-third NPN tube and one end of the thirteenth resistor and is connected with the reference current, the other end of the thirteenth resistor and the emitter of the twenty-third NPN tube are connected with the negative power supply voltage, the base of the twenty-third NPN tube and the emitter of the twenty-third NPN tube are connected with the negative power supply voltage through the fourteenth resistor, the collector of the twenty-third NPN tube is respectively connected with the base of the twenty-ninth PNP tube, one end of the fifteenth resistor and the collector of the twenty-fourth PNP tube, the other end of the fifteenth resistor is connected with the positive power supply voltage, the emitter of the twenty-fourth PNP tube is connected with the positive power supply voltage through the sixteenth resistor, the base of the twenty-fourth PNP tube is respectively connected with the collector of the twenty-fifth PNP tube, An emitter of the twenty-ninth PNP transistor; the base electrode and the collector electrode of the twenty-fifth PNP tube are connected, and the base electrode of the second sixteen PNP tube is connected in parallel with the base electrode of the second seventeenth PNP tube; the emitter of the twenty-fifth PNP tube is connected with the positive power supply voltage through the seventeenth resistor; the emitter of the twenty-sixth PNP tube is connected with the positive power supply voltage through the eighteenth resistor; the collector of the twenty-sixth PNP tube is respectively connected with the collector and the base of the thirty-sixth NPN tube; the emitter of the twenty-seventh PNP tube is connected with the positive power supply voltage through the nineteenth resistor; the collector of the twenty-seventh PNP tube is respectively connected with the collector of the twenty-eighth PNP tube and the base of the thirty-third NPN tube; the base electrode of the twenty-eighth PNP tube is respectively connected with the base electrode of the thirty-eighth NPN tube and one end of the twenty-second resistor, and connected with the output end of the input stage in parallel; the collector electrode of the twenty-eighth PNP tube is connected with the negative power supply voltage; the collector electrode of the twenty-ninth PNP tube is connected with the negative power supply voltage; the emitter of the thirty-eighth NPN tube is connected with the negative power supply voltage through the twentieth resistor; the base electrode of the thirty-first NPN tube is connected with the base electrode of the thirty-first NPN tube; the emitter of the thirty-first NPN tube is connected with the negative power supply voltage through the twenty-first resistor; the collector of the thirty-first NPN tube is respectively connected with the emitter of the fruit and vegetable thirty-second NPN tube and the base of the thirty-fourth PNP tube; the collector electrode of the third NPN tube is connected with the positive power supply voltage; the collector of the thirty-fourth PNP tube is connected with the negative power supply voltage; the emitting electrodes of the thirty-fourth PNP tube are respectively connected with the test end, The base electrode of the thirty-fifth NPN tube and the base electrode of the thirty-fourth PNP tube are connected with the positive power supply voltage, the emitter electrode of the thirty-fifth NPN tube is respectively connected with the emitter electrode of the thirty-fifth PNP tube and the other end of the twenty-second resistor, the collector electrode of the thirty-third NPN tube is connected with the positive power supply voltage, the emitter electrode of the thirty-third NPN tube is respectively connected with one end of the twenty-third resistor and the emitter electrode of the thirty-fourth PNP tube, and the other end of the twenty-third resistor is used as the output end of the output stage.
8. The operational amplifier with base current cancellation structure according to claim 7, wherein the ninth NPN transistor is matched to the eleventh NPN transistor such that a bias current flowing through the tenth NPN transistor is the same as a bias current flowing through the zeroth NPN transistor.
9. The operational amplifier with a base current elimination structure according to claim 8, wherein the twelfth PNP transistor is matched with the seventh PNP transistor and the eighth PNP transistor such that a current flowing through the eleventh NPN transistor after common mode feedback is half a current flowing through the ninth NPN transistor.
10. The operational amplifier with base current elimination structure according to claim 9, wherein the base current elimination structure eliminates the input pair base current by configuring the base voltage of the tenth NPN transistor such that the base voltage of the tenth NPN transistor is equal to the input common mode voltage of the input pair.

Description

Operational amplifier with base current eliminating structure Technical Field The present invention relates to the field of analog integrated circuits, and more particularly, to an operational amplifier with a base current cancellation structure. Background The operational amplifier is used as a core functional module of an analog integrated circuit, and is widely applied to key electronic equipment such as a data acquisition system, a high-precision Analog Front End (AFE), radio frequency signal processing, a high-resolution ADC/DAC interface and the like by virtue of the characteristics of high gain, high input impedance and low output impedance. With the rapid development of the fields of 5G communication, precise instruments, medical images and the like, strict requirements are put on the instantaneity, the accuracy and the fidelity of signal processing, and the operational amplifier is further pushed to evolve towards the multi-performance fusion direction of high speed, high voltage swing rate and low noise. In the core performance index of the operational amplifier, the high-speed characteristic is mainly characterized by Bandwidth (Bandwidth) and Slew Rate (SR) quantization, wherein the Slew Rate directly determines the transient response capability of the amplifier to a large signal, and is a key parameter for processing a rapidly-changing pulse or high-frequency modulation signal. The high slew rate means that the output stage needs to have the capability of rapidly providing a large driving current, while the low noise characteristic requires to effectively inhibit the inherent noise and circuit interference of the device, ensure the accurate amplification of weak signals, and the synchronous improvement of the two performances becomes a core requirement for meeting the requirements of high-end application. Compared with the CMOS process, the bipolar process can provide the integrated circuit with the characteristics of larger transconductance, larger gain, low noise, low offset and the like, so that the common high-speed low-noise operational amplifier is mainly used for the bipolar process. In some application fields, the requirement on equivalent input noise of the operational amplifier is very high, the input noise voltage of the operational amplifier is required to be reduced, the low noise characteristic is realized, the collector current of the differential input pair tube is required to be increased, but the increase of the collector current can synchronously increase the input bias current of the operational amplifier, the excessive input bias current can flow through an external input resistor or a feedback resistor to generate additional voltage drop on the resistor, the voltage drop can be directly overlapped into an input signal to form an indelible static error, and under the condition of large internal resistance of a signal source, the increased bias current can generate large noise. Disclosure of Invention The invention provides an operational amplifier with a base current eliminating structure, which solves the problems of insufficient low-frequency gain, insufficient small signal bandwidth, insufficient slew rate and overlarge system imbalance of the existing high-speed low-noise operational amplifier. The invention provides an operational amplifier with a base current eliminating structure, which comprises an input stage, wherein the input stage is connected with an input common mode voltage through an input pair, the base electrode of the input pair is connected with the base current eliminating structure, the emitter electrode of the input pair is connected with negative power supply voltage through a bias branch, the collector electrode of the input pair is connected with a common mode feedback circuit, and the common mode feedback circuit is used for providing bias for the base current eliminating structure so as to eliminate the base current of the input pair through the base current eliminating structure. In an embodiment of the present invention, the input pair tube includes a zeroth NPN tube and a first NPN tube, bases of the zeroth NPN tube and the first NPN tube are connected to the input common mode voltage, a source of the zeroth NPN tube is connected to a source of the first NPN and is connected to the bias branch, and a drain of the zeroth NPN tube and a drain of the first NPN tube are respectively connected to the common mode feedback circuit. In an embodiment of the present invention, the bias branch includes a ninth NPN tube and a first resistor, a base of the ninth NPN tube is connected to a negative bias voltage, a collector of the ninth NPN tube is connected to an emitter of the input pair tube, and the emitter of the ninth NPN tube is connected to a negative supply voltage through the first resistor. In an embodiment of the invention, the base current eliminating structure comprises a fourth PNP tube, a fifth PNP tube, a sixth PNP tube, a tenth NPN tube, a