A Precision Operational Amplifier with eTrim-Based Offset Calibration and Two-Point Temperature Drift Trim

This work introduces a trimming technique based on eTrim technology to minimize both the input-referred offset voltage and its temperature drift in the operational amplifiers. The proposed low-voltage op-amp utilizes the body effect to maintain a constant bandwidth across the rail-to-rail input common-mode range under low supply voltages. During input common-mode transitions, the current in the folded cascode stage remains stable, ensuring a robust output stage. Furthermore, a specialized gain-boosting structure enhances the low-frequency gain while preventing occasional latch-up during low-voltage power-up. A pin-multiplexing scheme is employed for trimming data input, thereby eliminating the need for dedicated trimming pins and mitigating post-package parameter variations. At room temperature, a constant-current injection mechanism reduces the DC offset to microvolt levels. At high temperature, temperature-compensated current injection cancels the first-order drift component. Implemented in a low-voltage operational amplifier, post-layout simulation results demonstrate that with a 100-pF capacitive load, the amplifier achieves a gain–bandwidth product exceeding 10 MHz, a low-frequency gain greater than 140 dB, and an input-referred noise of 2.54 µVp-p for the P-channel input and 3.95 µVp-p for the N-channel input. The trimming process reduces the residual offset to the microvolt range and effectively suppresses offset drift, ensuring accurate offset compensation across the specified temperature range.