Two-Stage Operational Amplifier

Abstract

The invention relates to a two-stage operational amplifier which comprises a first-stage operational amplification circuit, a second-stage operational amplification circuit, two common-mode feedback circuits, biasing circuits and a switch capacitance common-mode feedback circuit, wherein the biasing circuits are used for respectively providing biasing signals for the two common-mode feedback circuits; and the switch capacitance common-mode feedback circuit is taken as common-mode feedback of the first-stage operational amplification circuit. In the operational amplifier provided by the invention, the switch capacitance common-mode feedback circuit and the corresponding biasing circuit are additionally arranged for the first-stage operational amplification circuit, so that good matching between the common-mode output voltage of the first-stage operational amplification circuit and the input common-mode voltage of the second-stage operational amplification circuit is realized.

Description

【Technical field】 [0001] The invention relates to the field of analog integrated circuit design, in particular to a two-stage operational amplifier with common-mode voltage compensation. 【Background technique】 [0002] Integrated operational amplifiers generally adopt a fully differential structure, which can suppress common-mode interference and noise. However, the common-mode output voltage of the differential operational amplifier will deviate from the design value due to factors such as manufacturing process, operating voltage and temperature, so a common-mode feedback circuit is required to determine the output DC voltage. Stability needs to be considered when designing a common-mode feedback circuit. [0003] An integrated operational amplifier is a commonly used circuit unit. In order to achieve high gain and large output signal range, a two-stage structure is generally used. In order to ensure the stable operation of the feedback circuit formed by the operational ...

AI Technical Summary

Problems solved by technology

[0006] The conventional fully differential two-stage operational amplifier realizes the connection between the first stage and the second stage by designing the common mode output level of the first stage to be located in the center of the input voltage range of the second stage op amp. When the change causes the threshold voltage of the MOS tube to change, the input voltage range of the second-stage op amp will change, and the output voltage range of the first-stage op amp that can be handled becomes smaller.

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