A True Rail-to-Rail Input and Output Amplifier

Abstract

Operational amplifiers are basic building blocks of an analog system. As a system is only as good as its building blocks. There exists a constant need for developing a high-performance amplifier. Especially if they are configured as a buffer for analog front-end applications, as the system performance is highly dependent on the quality of input signal. Hence, they are critical for signal conditioning. This thesis presents a unity-gain stable operational amplifier for an ADC front-end application. The op-amp focuses on delivering high linearity with low noise and offset while driving a switched capacitor load. To accomplish this the op-amp employs Current Spillover, Chopping and Gain-Boosting techniques. The op-amp achieves THD of -108 dB at 10kHz, offset of 2.7 µV and input noise density of 19.3 nV/√Hz while consuming 504 µW; resulting in a NEF of 12.28. The op-amp is fabricated in 0.16 µm CMOS technology and occupies 0.1 mm2 area.