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Fully differential operational amplifier circuit for eliminating direct-current offset voltage

A technology of operational amplifiers and DC offsets, applied in differential amplifiers, DC-coupled DC amplifiers, amplifiers, etc., can solve problems such as loop oscillation and high requirements for operational amplifiers, achieve simplified circuit structure, simple implementation methods, and improve system stability Effect

Active Publication Date: 2020-04-17
SHANGHAI PANCHIP MICROELECTRONICS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This structure needs to be realized by using an operational amplifier in the feedback loop. The operational amplifier will not only bring additional power consumption, but also have high requirements on the operational amplifier, which will easily cause the loop to oscillate.

Method used

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  • Fully differential operational amplifier circuit for eliminating direct-current offset voltage
  • Fully differential operational amplifier circuit for eliminating direct-current offset voltage
  • Fully differential operational amplifier circuit for eliminating direct-current offset voltage

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Embodiment 1

[0032] Such as Figure 4 Shown is the circuit diagram of the specific embodiment 1 of the present invention, that is, a fully differential operational amplifier circuit for eliminating DC voltage, and the fully differential operational amplifier structure is a two-stage operational amplifier circuit with differential input and differential output.

[0033] Among them, VIP and VIN are differential input signals, VOP and VON are differential output signals, VDCP and VDCN are DC offset signals, VDD is power supply, VB is bias voltage, vfb is feedback voltage, VREF is reference voltage, VCM is common mode Voltage.

[0034] The first-stage operational amplifier module 1 is composed of P-type MOS transistors (MP1), P-type MOS transistors (MP2), N-type MOS transistors (MN1), N-type MOS transistors (MN2) and N-type MOS transistors (MN6). Among them, MN1 and MN2 are differential input tubes, MP1 and MP2 are load tubes; MN6 is a tail current source, which provides operating current for...

Embodiment 2

[0041] Such as Figure 5 As shown, on the basis of the first embodiment, the DC offset signal differential amplifier 5 in the second embodiment consists of an N-type MOS transistor (MN3 1 -MN3 n ), N-type MOS tube (MN4 1 -MN4 n ) and n bit control switch S 31 -S 3n and S 41 -S 4n constitute. Programmable through the control signal to achieve the adjustment of the DC level suppression.

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Abstract

The invention discloses a fully differential operational amplifier circuit for eliminating direct-current offset voltage. The circuit comprises a first-stage operational amplifier module, a second-stage operational amplifier module, a direct-current offset signal amplification module and a common-mode feedback operational amplifier module, wherein the differential input end of the first-stage operational amplifier module receives a differential input signal; the differential output end of the first-stage operational amplifier module is electrically connected to the differential input end of the second-stage operational amplifier module; the differential output end of the second-stage operational amplifier module outputs a differential output signal, and the direct-current offset signal amplification module acquires the differential output signal, filters the differential output signal to obtain a direct-current offset signal, amplifies the direct-current offset signal and sends the amplified direct-current offset signal to the differential output end of the first-stage operational amplifier module. The suppression of the DC level can be realized, the suppression degree of the DC level can be adjusted as required, the circuit structure is greatly simplified, and the implementation mode is simple.

Description

technical field [0001] The invention relates to the technical field of operational amplifiers, in particular to a fully differential operational amplifier circuit for eliminating DC offset voltage. Background technique [0002] Ideally, when the differential input voltage of the operational amplifier is zero, the differential output voltage of the operational amplifier should also be zero. However, due to the mismatch in the circuit, the output of the op amp is not 0 at this time, and the circuit has a DC offset, which is defined as the input voltage value when the output voltage is 0. [0003] There are basically three ways to eliminate DC offsets: AC coupling, switched capacitors, and low-pass negative feedback. [0004] AC coupling is a relatively easy implementation method. The implementation method is to add a coupling capacitor between the front and rear stages, and add a DC bias circuit near the input end of the second stage. However, when the signal frequency is rel...

Claims

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Application Information

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IPC IPC(8): H03F1/30H03F1/26H03F3/45
CPCH03F1/303H03F1/26H03F3/45479H03F3/45179
Inventor 孙伟黄继成
Owner SHANGHAI PANCHIP MICROELECTRONICS CO LTD
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