Current-reuse Low-Power Single-Ended to Differential LNA for Medical Ultrasound Imaging

We present a low power, low noise current-reuse fully differential OTA (Operational Transconductance Amplifier) -designed in 180 nm CMOS technology- having an energy efficient architecture including a common-mode feedback which ensures the conversion from single-ended to differential with close to zero power - the power being used when the capacitors are reset, no power is consumed in active mode time, the amplifier being designed for an active time of 500 mus. The amplifier drives a capacitive load of 200 fF and achieves 55 muW, an input-referred noise of 19 nV/ root Hz and an input capacitance of 18 fF for a unity gain frequency (fug) of 280 MHz. Since this circuit can be designed for a large range of frequencies, we also investigate the way of optimizing a figure-of-merit (FOM).