High Performance Operational Amplifier with 90dB Gain in SCL 180nm Technology

This paper presents the design and implementation of a high-speed, high-gain fully differential opamp. The architecture consists of a telescopic cascode differential amplifier followed by a modified common-source second stage that includes an intermediate push-pull stage, individual CMFB circuits including frequency compensation for the first and second stages, RC Miller compensation for the main op-amp, and dc bias circuit blocks. The circuit is implemented in SCL 180nm technology, including layout and post-layout extracted characterization. It achieves a DC gain of 90dB with phase margin of 58° at 530MHz for a load of 1pF. Output voltage swing is +/-600mV for a +/-900mV supply. A sample-and-hold circuit built with the op-amp gives an accuracy of 60µV at 40MHz.