An Ultra‐Low Power, Highly Linear, Fully Differential Programmable Gain Amplifier With 0.017%/V Line Sensitivity and 50‐mdB/°C Temperature Coefficient for Low‐Frequency Applications

This paper presents the design of a fully differential operational amplifier with four levels of programmable differential gain compensated for variation of temperature over a wide range. The design is optimized for low‐frequency applications and consumes a total power < 200 nW. Designed in planar 0.18‐μm CMOS technology, the amplifier offers four distinct gain levels between 6 dB and 16.5 dB with a robust average gain variation of 50 mdB/°C over a temperature ranging between −10°C and 90°C. Furthermore, an impressive average line sensitivity of helps all the four gain levels remain constant across 0.4‐V to 5‐V supply variations. High linearity is maintained with distortion for input signals ranging from 600 nV to 55 mV, yielding a dynamic range of approximately 75 dB. The circuit exhibits an offset voltage < 200 nV while occupying a silicon area of 0.86 mm 2 . All results, including the impact of parasitic elements and process variations, are validated post‐layout. These combined features establish the novelty of this work as a distinctive realization of a nanowatt‐level programmable gain amplifier that maintains both temperature and supply‐voltage‐invariant programmable gains, making it highly suitable for ultra‐low power IoT and biomedical applications. This amplifier is primarily intended as an additional programmable gain stage complementing a fixed‐gain pre‐amplifier in various low‐frequency applications.