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.