CMOS chopper-stabilized operational amplifier using two differential amplifier pairs as input stages

摘要

A CMOS chopper-stabilized operational amplifier including a nulling amplifier and a main amplifier has a pair of two input differential amplifiers in the input stage of each of the nulling amplifier and the main amplifier. In the nulling amplifier, one two-input differential amplifier switchably receives the input signals to the chopper stabilized operational amplifier, while the other two input differential amplifier functions in a feedback loop for developing a nulling voltage for the DC offset of the first two input differential amplifier. The operational amplifier has a three-phase clock and samples through a nulling time period, a setting time period, and a sampling time period.