A Fill-In Technique for Robust IMD Suppression in Chopper Amplifiers

In chopper amplifiers, the interaction between input signal and clock can give rise to intermodulation distortion (IMD). This chopper-induced IMD is mainly due amplifier delay, which causes large pulses at output of amplifier’s chopper. article proposes use a so-called fill-in technique eliminate these pulses, thus resulting IMD, by multiplexing outputs two identical amplifiers that are chopped in quadrature. A prototype chopper-stabilized was implemented 180-nm CMOS process. Measurements show suppresses 28 dB, an −126 dB for frequencies near 4 $F_{\mathrm {CH}}$ (=80 kHz). It also improves two-tone (with 79 80 kHz inputs) from −97 −107 same as obtained without chopping.