A wide linear range CMOS OTA and its application in continuous-time filters

Abstract

In this paper, we have proposed a highly linear Operational Transconductance Amplifier (OTA) with wide linear input range. The proposed OTA utilizes conventional source degeneration with an auxiliary differential pair which increases the linear range significantly by reducing the distortion components. The proposed OTA is targeted for current mode circuit applications including low-frequency continuous time filters. A second-order fully differential filter architecture is also implemented by using this proposed OTA. The linear OTA and the filter are implemented in SCL 180 nm CMOS process technology with 1.8 V supply voltage. The proposed OTA achieves third order harmonic distortion ($${\textit{HD}}_3$$) of $$-\,74.3$$ dB, inter modulation distortion ($${\textit{IM}}_3$$) of $$-\,75.5$$ dB for $$600\,\hbox{mV}_{p-p}$$ differential input with 1 MHz signal frequency and a linear range of 0.9 V for 1% transconductance variation. The filter is designed for 100 kHz cutoff frequency and achieves $${\textit{HD}}_3$$ of $$-\,68.75$$ dB and $${\textit{IM}}_3$$ of $$-\,64.3$$ dB for $$300\,\hbox{mV}_{p-p}$$, 10 kHz input signal.