A CMOS Chopper Amplifier

This paper presents a CMOS chopper amplifier realized with a 2nd order low-pass selective amplifier, using continuous-time filtering technique. The circuit has been integrated in a 3 μm p-well low-voltage CMOS technology. The chopper DC gain is 32 dB with 200 Hz bandwidth. The equivalent low-frequency input noise is 63 nV/√Hz and free from 1/f noise. The input offset is typically 5 μV. The amplifier consumes only 34 μW and is therefore well suited for biomedical applications, like electrogram amplification.