A CMOS chopper opamp with integrated low-pass filter

A CMOS chopper opamp has been realized. The low-pass filter, which is necessary to remove modulated offset and noise components, is implemented as a sample-and-hold filter, which has the advantages of not limiting the band width and easy integration. The opamp features an offset of 30 µV, noise of 300nV/√Hz, 120dB gain and 75 µW power consumption. The opamp has better trade-offs for offset, noise, chip area and power consumption than traditional auto-zeroed opamps.