A fast settling, high DC gain, low power OPAMP design for high resolution, high speed A/D converters

A fast settling, low power, high dynamic range OPAMP with a DC gain of 96 dB has been designed. Simulations have been performed in 0.35 /spl mu/m CMOS technology for slow, nominal and fast models. High DC gain has been achieved by adding gain boosting active blocks to the main OPAMP. In this design, a telescopic OTA has been chosen as the main opamp due to its fast settling and low power advantages, as well as the gain boosting OPAMPs. Transient simulation indicates a settling time of 17ns for a global feedback with /spl beta/= 1/2 . Although telescopic OPAMPs suffer from inherent low output voltage swing, a dynamic range of 83 dB has been achieved in this design. A power consumption of 4.1 mW is obtained for the total circuit including the main OPAMP, gain boosters and the bias circuitry.