application-note · English
MT-055 Tutorial: Chopper Stabilized (Auto-Zero) Precision Op Amps
This six-page tutorial from Analog Devices (MT-055) explains the operating principles of chopper-stabilized (auto-zero) precision op amps, covering the classic chopper architecture and the modern two-amplifier auto-zero topology used in IC implementations. It compares fixed versus pseudorandom chopping frequencies for intermodulation distortion, discusses the patented ping-pong auto-zero/chopper technique used in the AD8628/AD8629/AD8630 family, and provides noise performance data contrasting auto-zero amplifiers against precision bipolar types such as the OP177. Key design guidance notes that choppers should be selected for their ultralow offset and drift rather than their 1/f noise suppression, and that parasitic thermocouple effects in external circuitry must be avoided to realize full performance.