A CMOS Analog Front-End for Implantable Pulmonary Artery Pressure Monitoring System

This paper presents an energy-efficient analog front-end circuit to monitor the pulmonary artery pressure (PAP) with piezoresistive pressure sensors. A low-power capacitively-coupled instrumentation amplifier (CCIA) is developed in order to boost the amplitude of the bridge sensor to the input range of the analog-to-digital converter (ADC). The 1/f noise and input-referred offset of the amplifier are eliminated by the chopping technique. Simulation results show that this CCIA with chopping technique achieves an input-referred noise density of 38.7 nV/p Hz and an input-referred offset voltage of 4 mu V with a current consumption of 4.28 mu A at 1.8 V voltage supply. This gives a noise-efficiency factor (NEF) of 3.1. Dual supply voltages are used to decrease the power consumption of the bridge sensor. The pressure range is selected to be between 0 and 125 mmHg and the bandwidth of the interface is set from DC to 400 Hz with an RC low pass filter (LPF). This low-noise, low-offset analog front-end circuit achieves an accuracy of 0.125 mmHg.