Circuit structure for reducing input offset voltage of two-stage operational amplifier

Abstract

The invention provides a circuit structure for reducing input offset voltage of a two-stage operational amplifier, which comprises a switching control circuit, a first-stage differential amplification circuit, a second-stage common-source amplification circuit and a compensation network, wherein the output end of the switching control circuit is connected with the input end of the first-stage differential amplification circuit, the output end of the first-stage differential amplification circuit is connected with the input end of the second-stage common-source amplification circuit, and the compensation network is further connected between the input end and the output end of the second-stage common-source amplification circuit. The circuit structure has the benefits that the offset of the operational amplifier is reduced by adopting an MOS (metal oxide semiconductor) switching tube to control and exchange signals at the positive and the negative input ends and the signals at the output end of the operational amplifier; as only the MOS switching tube is increased in the circuit, the circuit structure only needs very small area and very low power consumption; and the circuit does not affect the gain of the operational amplifier, the phase margin, the power supply voltage rejection ratio, the common-mode input range and other performance indexes while reducing the input offset voltage of the operational amplifier, and can be applied in mainstream CMOS (complementary metal oxide semiconductor) circuit systems.

Description

Technical field [0001] The invention belongs to the technical field of microelectronics and solid-state electronics, and relates to an operational amplifier circuit of an integrated circuit, in particular to a circuit structure for reducing the input offset voltage of a two-stage operational amplifier. Background technique [0002] Operational amplifiers are widely used in analog circuits and digital-analog hybrid circuits. As CMOS technology has become the mainstream technology of integrated circuits, compared with traditional bipolar circuits, CMOS operational amplifier circuits have significant advantages in cost and development cycle. The current design idea of ​​reducing the offset voltage of the operational amplifier is to use chopping technology and automatic zeroing technology, but the chopping technology needs to couple the input signal and the switching square wave signal, and then obtain the result after synchronous demodulation and low-pass filtering. Signals with lo...

AI Technical Summary

Problems solved by technology

The current circuit design idea of ​​reducing the offset voltage of the op amp is realized by using chopper technology and automatic zero adjustment technology, but the chopper technology needs to couple the input signal with the switch-type square wave signal, and then obtain it after synchronous demodulation and low-pass filtering. For small non-linear signals, the circuit complexity increases, which will significantly increase the circuit area; the automatic zeroing technology needs to store the offset in the capacitor, mainly including input offset storage and output offset storage, and is mainly suitable for discrete signal circuits such as switched capacitors.

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