A CMOS Chopper Offset-Stabilized Opamp

In this paper we introduce an offset-stabilized operational amplifier that uses a chopper amplifier in a low frequency path to cancel the offset of a wide-bandwidth amplifier. A sample-and-hold circuit is used to reduce the chopper ripple, and the low frequency path is also offset-stabilized to further reduce the residual offset. The amplifier has 1muV offset at a 4 kHz chopper frequency, and a unity gain frequency of 1.3MHz with a 50pF load. The amplifier was realized in a 0.7mum CMOS process, and has an effective chip area of 3.6mm
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