A novel low power high CMRR pseudo-differential CMOS OTA with common-mode feedforward technique

Abstract

This paper presents a novel low-power (LP) pseudo-differential (PD) CMOS operational transconductance amplifier (OTA). The proposed OTA is based on a feedforward cancellation of the input common mode signal at the output nodes in order to enhance the common-mode rejection ratio (CMRR) with the minimum cost of area, the power consumption and the parasitic components. By means of the proposed configuration of the common-mode feedforward (CMFF) technique, the transconductance gain of this OTA is almost two times and four times the transconductance gain of the traditional CMFF OTAs. It also reduces the power needed in comparison with the traditional CMFF OTAs to achieve the same transconductance gain. The post-simulation results shows that the proposed OTA has a 46.4 dB DC gain, a 14.5 MHz gain bandwidth (GBW) and a 85° phase margin for 2 PF capacitive loads. The proposed OTA achieved 110.1 dB CMRR. The OTA consumes only 28.6 μW under a 1.2 V single supply voltage and occupies a very small area of 33 × 10−5 mm2. This OTA is designed and simulated by the TSMC 0.18 μm CMOS process.