A Low-Power Low-Voltage Amplifier for Heart Rate Sensor

The demand for health-monitoring products is increasing worldwide. Low-power and low-voltage attributes are important concerns that need to be addressed in circuits used for personal health-monitoring applications, to achieve a long battery life. In this paper, a low-power low-voltage OTA used in a heart rate sensor is presented in a MOS-bipolar pseudo-resistor configuration. Super source degeneration, bulk driving and adjustable transconductance techniques are applied to achieve low power and low-voltage criteria. The OTA consumes current of 700 nA from a 1V single supply. As per the simulations, the circuit achieves 22kHz bandwidth (from 50mHz to 22kHz) at a closed loop gain of 14dB while driving a load capacitance of 80pF. The circuit is implemented in 0.18mum CMOS technology