Opamp for a 10/12 bits Sigma Delta ADC

Abstract

This master thesis describes the design of a low-voltage fully differential Op-erational Amplifier (OPAMP), which is supposed to work as an integratorin a Sigma Delta (Σ∆) analog to digital converter (ADC). Since the ADCin 130nm CMOS process is still under research, challenging conditions havebeen established.The OPAMP operates with a supply voltage range of 1.2 V ±10%, at tem-peratures between -40◦C and 105◦C and at different process corners.The thesis presents the design decisions, design phase and the theory neededto understand the chosen topology and architecture.Results are based on SPICE simulations, showing that the designed OPAMPoperates correctly at different combination of corners, temperatures and sup-ply voltages. The results obtained in most cases show a typical ac gain of85dB, unity gain bandwidth of 33MHz, phase margin of 53◦and a slewrate of 11V/µs. However with a supply voltage as low as 1.08V at -40◦C, theOPAMP s performance is deteriorated. Thus a better bias control is requiredfor correct performance at the lowest supply voltage.