A Subthreshold CMOS Inverter-Based Amplifier for Low Power and Low Noise Applications

A CMOS inverter-based amplifier is presented for low power and low noise applications. Unlike conventional analog amplifiers with MOSFETs operating in saturation region, the transistors in the proposed amplifier operate in subthreshold region, enabling it to minimize the power supply current, which ultimately results in lower power consumption and lower noise. The proposed single-stage amplifier consists of only 3 transistors and is guaranteed to be stable. As proof of concept, the specs of the proposed amplifier are successfully measured and verified by a test chip designed and fabricated in 3.3 V TSMC’s 180nm CMOS process. The fabricated amplifier operates at 1.2 V power supply with the measured voltage gain of 51 dB (or 350 $\mathrm{V}/\mathrm{V}$), bandwidth of 27 kHz, and the equivalent input voltage noise of 7 $\mathrm{n}\mathrm{V}/\sqrt{}\mathrm{H}\mathrm{z}$, consuming only 2 $\mu \mathrm{W}$. For different applications the required specs can be achieved by optimizing the transistor sizes used in this circuit topology.