A Single-Temperature Trimming Technique for MOS-Input Operational Amplifiers Achieving 0.33 μV/∘C Offset Drift

A MOS-input operational amplifier has a reconfigurable input stage that enables trimming of both offset and offset drift based only on single-temperature measurements. The input stage consists of a MOS differential pair, whose offset drift is predicted from offset voltage measurements made at well-defined bias currents. A theoretical motivation for this approach is presented and validated experimentally by characterizing the offset of pairs of discrete MOS transistors as a function of bias current and temperature. An opamp using the proposed single-temperature trimming technique has been designed and fabricated in a 0.5 μm BiCMOS process. After single-temperature trimming, it achieves a maximum offset of ± 30 μV and an offset drift of 0.33 μV/°C (3σ) over the temperature range of -40°C to +125°C.