Ultra Low-voltage, rail-to-rail input/output stage Operational Transconductance Amplifier (OTA) with high linearity and its application in a Gm-C filter

Farzan Rezaei and Seyed Javad Azhari
Department of Electronics/Electronics Research Center, Iran University of Science and Technology (IUST)


This paper presents an ultra low-voltage, rail-to-rail input/output stage Operational Transconductance Amplifier (OTA) which uses quasi floating gate input transistors. This OTA works with ±0.3v and consumes 57µw. It has near zero variation in small/large-signal behavior (i.e, transconductance and slew rate) in whole range of the common mode voltage of input signals. Using source degeneration technique for linearity improvement, make it possible to obtain

-42.7 dB, HD3 for 0.6vP-P sine wave input signal with the frequency of 1MHz. The used feedback amplifier in input stage also enhances common mode rejection ratio (CMRR), such that in DC, CMRR is 146 dB. OTA is used for implementation of a wide-tunable third-order elliptic filter with 237 KHz-2.18 MHz cutoff frequencies. Proposed OTA and filter have been simulated in 0.18µm TSMC CMOS technology with Hspice.