JSSC 2021第12期Clocking & PLLs180nmNeural Network Accelerator

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

提出填充技术抑制斩波放大器中的互调失真，提升性能。

IMD抑制28 dB，两音IMD从-97 dB提升至-107 dB

斩波放大器互调失真填充技术CMOS正交斩波

▸使用填充技术消除斩波引起的互调失真

▸通过正交斩波复用两个相同放大器的输出

▸显著提升放大器的两音互调失真性能

Abstract

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