An Ultra-Low Power, High-Linearity, 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 an ultra-low power, fully differential operational amplifier with programmable differential gain, optimized for low-frequency applications. Designed in planar 0.18 µ m CMOS technology, the amplifier offers four distinct gain levels between 6 dB and 16.5 dB. A novel approach ensures robust temperature compensation, limiting average gain variation to 50 mdB/ ◦ C over a temperature range from –10 ◦ C to 90 ◦ C range. Furthermore, the design achieves an impressive average line sensitivity of 0.017%/ V across 0.4 V to 5 V supply variations. High linearity is maintained with <%1 distortion for input signals ranging from 600 nV p . p to 55 mV p . p , yielding a dynamic range of approximately 75 dB.The circuit exhibits an offset voltage < 200 nV while consuming a maximum power of 180 nW, occupying a silicon area of 0.86 mm 2 . All results, including the impact of parasitic elements and process variations, are validated post-layout. This amplifier is primarily intended as an additional programmable gain stage complementing a fixed-gain pre-amplifier in various low frequency applications.