Ultra-Low Power High Sensitivity Photoplethysmography Sensor Based on Inverted Cascode Transimpedance Amplifier Using Quasi-Floating Gate

This paper presents a design and simulation results for a Photoplethysmography (PPG) sensor front-end circuitry. An ultra-low power consumption is achieved since proposed integrated inverted cascode Transimpedance Amplifier (TIA) is incorporating a quasi-floating gate (QFG) topology. The proposed TIA has 0.3 Hz high-pass frequency that is less than the lowest frequency of PPG signal. The designed transimpedance gain of the proposed TIA is 119.9 dBΩ using a large area photodiode having a 20 pF capacitance. The TIA is followed by a Post Amplifier (PA) to increase the gain to 148.5 dBΩ. A buffer amplifier is desired as a last stage to drive the load capacitance of the next stage analog to digital converter (ADC). This proposed sensor system bandwidth is 4.5 kHz with an integrated input referred noise of 94 pA that is the average valued from Monte-carlo simulation. The total power consumption by the sensor front-end is approximately 30 μW.