Design of a Low-Level Offset Op Amp using Ping Pong Auto Zeroing Architecture

Abstract

Small signal input is used in a variety of electronic industries. These systems must have a very small offset value and offset drift with respect to time and temperature. These fields necessitate a high level of precision. Precision amplifiers are used in various fields like automotive, instrumentation, electronics and industrial fields, all of which need a reasonable price and simplicity. For a precision op amp, offset voltage should be minimum and output will be continuous. This paper presents a ping pong auto zeroing architecture for offset cancellation and continuous output provision. There are various methods for offset cancellation like chopper amplifier method, auto zeroing method and chopper stabilized method but these all have some drawbacks like chopper method have low bandwidth problem and auto zeroing method cannot provide continuous output. So we want to explain a precision amplifier with ping pong AZ (auto zeroing) method that can deliver very low offset and offset drift with respect to temperature, as well as continuous performance. The architecture was realized in 0.5μm CMOS process with 5V supply voltage and 1.5 mA supply current. The measurement result shows 138 dB CMRR, 118 dB PSRR, rising and falling slew rate of +2 volt/μsec and −2.10 volt/μsec respectively.