Opamp with 106 dB DC gain in 120nm digital CMOS

A three-stage operational amplifier employing only regular-threshold devices in a 120nm digital CMOS technology with a gain-boosted folded-cascode input stage and a class AB rail-to-rail output stage is presented. The gain boost results in a low-frequency differential gain of 106dB at a supply voltage of 1.2V. A bulk regulator of the input transistors increases the input-voltage range to -0.1...+1.0V. A gain-bandwidth product of 57MHz and a phase margin of 71/spl deg/ are measured for loads of 5.5pF.