A 55 V, Six-Channel Chopper and Auto-Zeroing Amplifier with 6.2 nV/Hz Noise and −128 dB Total Harmonic Distortion

In this paper, a high-voltage chopper and ping-pong auto-zeroing operational amplifier was designed for industrial and automotive applications. Based on chopper stabilization, the proposed circuit introduces a novel chopper switch control signal that varies with the input common-mode voltage. This scheme effectively suppresses the reference offset caused by the chopper switches and prevents transistor breakdown under high-voltage conditions. Additionally, the ping-pong auto-zero structure was optimized by employing a six-channel parallel first-stage amplifier, which further reduced the charge injection and ripple introduced by the chopper switches. The amplifier was implemented using an SMIC (Semiconductor Manufacturing International Corporation) 180 nm 1P5M BCD (Bipolar-CMOS-DMOS) process with a chip area of 4.211 mm2. The post-layout simulation results show that, under a 55 V supply, the amplifier achieves an input-referred noise Power Spectral Density (PSD) of 6.2 nV/Hz and an input offset voltage of 32 μV, while the output voltage swings from 0.2 V to 53.4 V with a unity gain bandwidth of 3.2 MHz, which meets the requirements for high-voltage, high-resolution signal processing.