TWO-STAGE FULLY-DIFFERENTIAL OTA FOR A 10-BIT 40-MSAMPLES/S CMOS ANALOG-TO-DIGITAL CONVERTER

Abstract

A two-stage fully-differential Operational Transconductance Amplifier (OTA) for a 10-bit 40-Msamples/s Nyquist rate Analog-to-Digital Converter (ADC) using 0.35μm Complementary Metal-Oxide Semiconductor (CMOS) process is presented. A telescopic cascode topology is employed as main stage, with common source amplifiers as output stage for the differential outputs. The open loop amplifier achieved a gain of 108dB. The closed loop OTA has gain of 4 with settling time less than 11ns for an accuracy of 0.5%. Total output noise achieved is 63.4uVrms. Loop unity gain bandwidth is 205MHz with phase margin of 77.6degrees. The design has a dynamic range of 88.3dB. On the average, the amplifier dissipates 26.6mW of power from a 3V supply.