A Three-Stage Operational Transconductance Amplifier for Delta Sigma Modulator

Abstract

The design and simulation of a low power, high gain three stage operational transconductance amplifier (OTA) is presented. This OTA has a DC gain of 73.5 dB, a unity gain bandwidth (UGB) of 39.8 MHz and a phase margin of 59°. The total power consumed by OTA is 332 μW. The DC gain and the power dissipation parameters of the OTA are found to be better than the previously published results of [1]–[4].Further, a first order Delta Sigma Modulator (DSM) is designed as a vehicle to test the OTA by integrating it with a comparator and a DAC for a signal bandwidth of 2 kHz with an oversampling ratio (OSR) of 250 for low frequency biomedical applications. All the blocks are designed using UMC 180nm CMOS 1P9M technology, with 1.8 V supply voltage. The simulation results show that the in-band signal to noise and distortion ratio (SNDR) of the DSM is 53 dB, which is equivalent to 8.5 effective number of bits (ENOB).