CN217363034U

CN217363034U - Low-offset chopping operational amplifier

Info

Publication number: CN217363034U
Application number: CN202221196647.2U
Authority: CN
Inventors: 黄立朝; 徐凯英; 丁宁; 章宇新
Original assignee: CETC 58 Research Institute
Current assignee: CETC 58 Research Institute
Priority date: 2022-05-18
Filing date: 2022-05-18
Publication date: 2022-09-02
Anticipated expiration: 2032-05-18

Abstract

The utility model relates to a low imbalance operational amplifier, including oscillator module, chopper switch module, gain module. The oscillator module is used for generating a basic clock signal, the clock signal is converted into two chopping signals with different frequencies after frequency division, an input signal is input into the operational amplifier after being modulated by the chopping signals, and the input offset voltage can be greatly reduced after the operational amplifier is cascaded, so that high-precision amplification is realized. The utility model discloses a low maladjustment chopper operational amplifier adopts the chopping modulation technique, and the maladjustment voltage is low to 50uV is put in fortune. Compared with the operational amplifiers of the same type, the offset of the amplifier is obviously reduced, the open-loop gain reaches 130dB, the high gain is realized, meanwhile, the extremely small offset drift is ensured, and the amplifier has a good application prospect when being used in miniature electronic equipment such as a sensor and the like.

Description

Low-offset chopping operational amplifier

Technical Field

The utility model relates to a high accuracy operational amplifier field especially indicates a low imbalance chopper operational amplifier.

Background

The CHOPPER operational AMPLIFIER (CHOPPER AMPLIFIER) is a low-noise and high-precision AMPLIFIER based on a CHOPPER modulation technology, is mainly applied to a sensor system and is used for amplifying a front-end sensor signal so as to enable the front-end sensor signal to be accurately identified by a rear-stage analog system. A sensor is an element that converts a physical quantity into an electrical signal, and is of many kinds, such as a temperature sensor (thermistor, thermocouple), a piezoelectric sensor (piezoelectric ceramic), a photoelectric sensor (photodiode), a hall device, and the like. Although the variety, shape, structure and physical mechanism of the sensor are numerous, it has a common feature: the response of the sensor to the input signal (i.e., the output signal of the sensor) is small in magnitude and generally cannot be used directly, especially in noisy environments. This makes low noise, low offset, high precision operational amplifiers essential in such systems.

SUMMERY OF THE UTILITY MODEL

In order to solve the above technical problem, the utility model discloses a low imbalance chopper operational amplifier contains following module: the chopping switch module comprises chopping switches CH1, CH2, CL1 and CL2, the oscillator module generates a basic clock signal, and the basic clock signal is divided by a frequency divider to generate two chopping frequencies f with different frequencies _CH \f _CL The input signal is modulated into an AC signal by the chopping switches CL1 and CH1 and sent to the gain module, and then the AC signal is demodulated by the output chopping switches CH2 and CL2 and passes through the low-pass filter, so that the accurately amplified input signal can be obtained.

In an embodiment of the present invention, the chopper switch is controlled by the switching signal generated by the oscillator, wherein the oscillator module employs a relaxation oscillator, the relaxation oscillator includes constant current sources I1 and I2, controllable switches switch1 and switch2, a high-side comparator and a low-side comparator and logic control, and a capacitor C, the constant current source I1 is disposed between vcc and the controllable switch1, the constant current source I2 is disposed between ground and the controllable switch2, one end of the capacitor C is grounded, the other end is disposed between the controllable switches switch1 and switch2, the high-side comparator and the low-side comparator, and the logic control part is connected to the output end of the high-side comparator and the low-side comparator.

In an embodiment of the present invention, the gain module is composed of cascaded operational amplifiers, the gain module adopts a triple operational amplifier structure, the first stage is a gain stage Gm, the second stage is a transimpedance R, and the third stage is a common mode compensation stage and a miller compensation for eliminating a feedforward path.

In one embodiment of the present invention, the two amplifiers in the gain module apply a differential input signal to the input of a resistive feedback network, the feedback network has a fixed 50-gain, and the final output voltage at the output is V _out ＝50*V _in +V _ref 。

6. In an embodiment of the present invention, the chopper switch and the cascaded chopper amplifier in the gain module form a three-stage amplifying circuit.

Compared with the prior art, the technical scheme of the utility model have following advantage: general cascade chopping operational amplifier, the circuit realizes the function that a cascade chopping (NESTED-CHOPPER) fortune was put, can realize analog signal's accurate amplification processing in certain frequency range. The circuit is designed and manufactured based on the BCD process, and is reliable in performance and high in practicability.

Drawings

In order to make the content of the present invention more clearly understood, the present invention will be described in further detail with reference to the following embodiments of the present invention, in conjunction with the accompanying drawings.

Fig. 1 is a flow chart of the operation structure of the low-offset chopping operational amplifier of the present invention;

fig. 2 is a diagram of the cascade structure of the amplifier of the present invention;

fig. 3 is a circuit diagram of an oscillator module according to the present invention;

fig. 4 is the whole circuit structure of the chopper amplifier of the present invention.

Detailed Description

As shown in fig. 1, the present embodiment provides a low offset chopping operational amplifier, which includes the following modules: the chopping switch module comprises chopping switches CH1, CH2, CL1 and CL2, the oscillator module generates a basic clock signal, and the basic clock signal is divided by a frequency divider to generate two chopping frequencies f with different frequencies _CH \f _CL The input signal is modulated into an AC signal by the chopping switches CL1 and CH1 and sent to the gain module, and then the AC signal is demodulated by the output chopping switches CH2 and CL2 and passes through the low-pass filter, so that the accurately amplified input signal can be obtained.

The oscillator module adopts a traditional relaxation oscillator as a circuit, charges and discharges a capacitor through a periodic switch, a voltage value of the capacitor is input into a comparator, and a periodic oscillation signal is generated by setting a threshold value of the comparator. And a chopping switch module, wherein the switch is controlled by complementary clock signals, and the frequency is called chopping frequency. The gain module is composed of cascaded chopper amplifiers, and the influence of the offset voltage on the output can be eliminated through the cascaded chopper amplifiers.

The chopping switch is controlled by a switching signal generated by an oscillator, wherein the oscillator module adopts a relaxation oscillator, as shown in fig. 3, the relaxation oscillator comprises constant current sources I1 and I2, controllable switches switch1 and switch2, a high-level comparator and a low-level comparator, a logic control and a capacitor C, the constant current source I1 is arranged between vcc and the controllable switch1, the constant current source I2 is arranged between ground and the controllable switch2, one end of the capacitor C is grounded, the other end of the capacitor C is arranged between the controllable switches switch1 and switch2, the high-level comparator and the low-level comparator, and the logic control part is connected with the output ends of the high-level comparator and the low-level comparator.

And further, its working principleComprises the following steps: upon power up, the capacitor voltage V _C When the voltage is low, the voltage is input into the window comparator to generate a logic signal, the switch1 is controlled to be turned on, the switch2 is controlled to be turned off, namely, the current source charges the capacitor C, and the voltage on the capacitor continuously rises until the voltage rises to a high threshold point V set by the high-level comparator _H (ii) a At this time, the output logic jumps, so that the switch1 is turned off, the switch2 is turned on, that is, the current source I2 discharges the capacitor C, and at this time, the capacitor voltage continuously decreases until the voltage decreases to V set by the low-level comparator _L So that the output logic jumps again, and the circuit enters a charging state again, and continuous oscillation waveforms can be output on the capacitor repeatedly.

The gain module is composed of cascaded operational amplifiers, the gain module adopts a three-operational-amplifier structure, the first stage is a gain stage Gm, the second stage is a transimpedance R, and the third stage is a common-mode compensation stage and Miller compensation for eliminating a feedforward path.

As shown in FIG. 2, the two amplifiers in the gain block apply a differential input signal to the input of a resistive feedback network with a fixed 50(34dB) gain, resulting in an output voltage at the output of V _out ＝50*V _in +V _ref 。

As shown in fig. 4, the chopping switch and the amplifier in the gain module form a three-stage amplifying circuit, and the chopping amplifier is cascaded. The offset voltage is smaller, and a high-precision signal amplification function is realized. The utility model discloses low offset chopper amplifier circuit can accomplish the high accuracy of small signal, low offset and enlarge.

Compared with the prior high-precision amplifier, the utility model discloses a low imbalance chopper amplifier, the imbalance voltage is lower, can cascade multistage chopper amplifier, and it has fine market prospect to be applied to high precision fields such as sensor.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious changes and modifications can be made without departing from the scope of the invention.

Claims

1. A low-offset chopping operational amplifier is characterized by comprising the following modules: the chopping switch module comprises chopping switches CH1, CH2, CL1 and CL2, the oscillator module generates a basic clock signal, and the basic clock signal is divided by a frequency divider to generate two chopping frequencies f with different frequencies _CH \f _CL The input signal is modulated into an AC signal by the chopping switches CL1 and CH1 and sent to the gain module, and then the AC signal is demodulated by the output chopping switches CH2 and CL2 and passes through the low-pass filter, so that the accurately amplified input signal can be obtained.

2. The low-offset chopping operational amplifier according to claim 1, wherein: the chopper switch is controlled by a switching signal generated by an oscillator, wherein the oscillator module adopts a relaxation oscillator which comprises constant current sources I1 and I2, controllable switches switch1 and switch2, a high-level comparator, a low-level comparator, a logic control and a capacitor C, the constant current source I1 is arranged between vcc and the controllable switch1, the constant current source I2 is arranged between ground and the controllable switch2, one end of the capacitor C is grounded, the other end of the capacitor C is arranged between the controllable switches switch1 and switch2, the high-level comparator and the low-level comparator, and the logic control part is connected with the output ends of the high-level comparator and the low-level comparator.

3. The low-offset chopping operational amplifier according to claim 1, wherein: the gain module is composed of cascaded operational amplifiers, the gain module adopts a three-operational-amplifier structure, the first stage is a gain stage Gm, the second stage is a transimpedance R, and the third stage is a common-mode compensation stage and Miller compensation for eliminating a feedforward path.

4. The low-offset chopping operational amplifier of claim 3, wherein: said gainTwo amplifiers in the module apply differential input signals to the input of a resistive feedback network with a fixed 50 gain, resulting in an output voltage at the output of V _out ＝50*V _in +V _ref 。

5. The low-offset chopping operational amplifier according to claim 1, wherein: the chopping switch and the cascaded chopping amplifier in the gain module form a three-stage amplifying circuit.