A SYSTEMATIC gm/ID-BASED DESIGN OF TWO-STAGE OTA FOR LOW-POWER APPLICATIONS IN 180nm CMOS

Electronics Engineering

This paper presents a systematic gm/ID-based design of a two-stage operational transconductance amplifier (OTA) optimized for low-power applications in 180nm CMOS technology. OTAs are integral components in analog front-end systems used in applications such as biosignal processing, wireless communication, and portable instrumentation, where power and area efficiency are critical. The gm/ID methodology offers a modern design framework that enables engineers to analyze and optimize transistor performance across weak, moderate, and strong inversion regions. Unlike traditional square-law-based methods, this technique provides greater flexibility and insight by directly relating transistor sizing to circuit-level specifications such as gain, bandwidth, and power consumption. In this work, we leverage the gm/ID technique to design a two-stage OTA that satisfies stringent performance requirements while maintaining low power consumption. The circuit is simulated in OrCAD PSpice to verify key analog parameters, including voltage gain and phase margin, and physically implemented in Cadence Virtuoso to ensure layout compliance with foundry design rules. The proposed OTA achieves a gain of 500 V/V, a unity-gain bandwidth of 93 MHz, and a phase margin of approximately 65°, with power consumption below 0.3 mW. Compared to conventional design methods, the gm/ID-based OTA demonstrates improved energy efficiency and design flexibility. The results validate the suitability of this approach for analog front-end systems in portable and low-voltage environments.

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