Design of an Automotive Sensor Readout Class AB CMOS Amplifier for Maximum Robustness Against Transient Electromagnetic Interference

A Class AB amplifier inherently robust against transient electromagnetic interference (EMI) of up to 220 V subjected to its output is presented in this work. The amplifier is the back end of an automotive IC which also includes an EMC-robust supply system and a 12-bit DAC. The design objective was not to just fulfil the latest transient EMC specifications but to exceed them as much as practically possible and this without using any external capacitive load. The amplifier uses a 1 nF integrated metal-insulator-metal (MIM) capacitor at its output together with Schottky diode arrays which are placed beneath the capacitor. Designed in 0.18 µm CMOS silicon-on-insulator (SOI) technology, the amplifier occupies an area of 0.66 mm2 and draws 1 mA quiescent current from a 5 V supply. To validate the effectivity of the proposed circuitry, measurement results extracted from a test chip are provided.