A supply-scalable differential amplifier with pulse-controlled common-mode feedback

This paper proposes a pulse-controlled common-mode feedback circuit for a supply-scalable fully-differential amplifier. The pulse-controlled common-mode feedback circuit overcomes the large area cost associated with a conventional R-C common-mode feedback circuit while maintaining high gain and large output signal range of the amplifier. The amplifier is implemented in low power/leakage 65nm CMOS technology with NMOS and PMOS threshold voltages of 0.36V and -0.44V and operates at a supply voltage from 0.6V to 1.2V. The prototype has an active area of 0.01mm² and consumes 1.21mW at 0.6V, 1.94mW at 0.9V and 3.07mW at 1.2V. The measured output noise spectrum density is 21.5nV/√Hz at 0.6V, 26.1nV/√Hz at 0.9V and 30.3nV/√Hz at 1.2V. For a total harmonic distortion of 1%, the maximum signal of the amplifier with frequency 10MHz is measured as -2.3dBm at 0.6V, 3.8dBm at 0.9V and 6.1dBm at 1.2V; as expected, the linearity of the amplifier depends on its signal headroom which scales with the supply voltage.