Design of Second Order Low Pass Filter Using Inverter-Based CMOS Operational Transconductance Amplifier (OTA) Through gm/ID Methodology

This paper introduces the design of an inverter-based CMOS operational transconductance amplifier (OTA) utilizing the $g_{m}/I_{D}$ methodology. The approach begins by representing the inverter as an amplifier with $g_{m}$ being the transconductance and $I_{D}$ being the drain current when both transistors are in the saturation region. Through this methodology, performance metrics such as gain, bandwidth, and output swing are optimized to meet specific application requirements. The paper highlights an optimized version of Nauta's OTA circuit, designed with the $g_{m}/I_{D}$ approach in a 0.18 $\mu \mathrm{m}$ CMOS technology node, and examines the design of a second-order low-pass filter using the OTA. With the 0.18 $\mu \mathrm{m}$ CMOS process, the designed second-order low-pass filter achieves a tuning ratio of 20, a total power consumption of 5.1 mW, and a 3 dB bandwidth ranging from 10 MHz to 79 MHz.