A 147dBΩ, High Dynamic Range Analog Front End for PPG Signal Acquisition with Fine and Coarse Steps Automatic Gain Control

This paper deals with the design of a low power, high-gain, low noise and high-dynamic range receiver dedicated for photoplethysmography (PPG) signal sensing. A current measurement system utilizing a large DC cancelation block, implemented in 180nm CMOS technology. The shunt feedback trans-impedance amplifier (TIA) is designed to detect and sense low currents, producing a voltage output. It exhibits a noise floor of 39.7 pArms within the frequency range of 0.5-10Hz. The receiver gain is 147.6dBΩ. The receiver incorporates a fine and coarse steps gain control block (FaCGC) and a DC cancelation block capable of handling up to 100µA, thereby enabling a wide dynamic range. The proposed system exhibits characteristics such as low noise and wide dynamic range, rendering it well-suited for the precise measurement of ultra-low current. Consequently, this system holds significant potential for application in biosensor technology. The chip has a footprint of 0.121mm2 area and operates with a power consumption of 40.14 micro-watts, drawing power from supply voltages of ±0.9 volts. The post-layout simulation reveals a lower frequency limit below 1mHz, while the upper limits of its application band can be extended up to 100 Hz.