Design of Sensor interface circuit for Bloodbeat measurement using photoplethysmogram

Photoplethysmogram is widely used to measure heart rate and arterial blood oxygen saturation in hunman. A Sensor interface circuit for circuit for Bloodbeat measurement using PPG(Photoplethysmogram) is proposed and designed by using current-control schmitt trigger in this paper. This circuit detects the blood beat using PPG which occurs in bloodbeat sensor and composed of analog and digital blocks. Current signal of sensor is converted into voltage in analog parts and then converted into digital signal in digital parts. Compared to the conventional method, operation speed is increased and linear error is diminished by applying OTA(Operational transconductance amplifier) to Schmitt trigger circuit and oscillator. Also, proposed and designed circuit has some features of low power consumption, simple structure and high resolution compared with previous method.