PPG Transimpedance Amplifier Circuit

Noor Diana, Abdul Samat (2006) PPG Transimpedance Amplifier Circuit. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

A photoplethysmograph (PPG) is a method of detecting human pulse with principal of correlation analysis. A PPG is described that performs a frequency analys is of the peripheral volume pulse wave. A Trans-impedance amplifier is used to convert current received from the photodiode to voltage for future processing. The pulse detector receives information in terms of an analogue signal. Pulse carrier is low-frequency signal with upper informative frequency. Therefore to raise the method performance we apply low-pass filter, lOOHz. A low-pass filter passes relatively low frequency components in the signal but stops the high frequency components. The so-called cutoff frequency divides the pass band and the stop band. In other words. the frequency components higher than the cutoff frequency will be stopped by a low-pass filter. This project also develops a low noise Pulse Sensor through Correlation Analysis (Lock-In). The lock-In acts like an Amplitude Modulation used Multiplication of reference signal and measured signal. Through correlation analysis or lock-in, noi ses that exist in measured signal can be rejected. Lock-In is capable to improve the Signalto- Noise ratio significantly: The band-pass filter cuts simply out a more or less broad part of the noise power spectrum in the vicinity of the input signal. hereby reducing the average relative noise power at the output, or the relative rms noise voltage. respectivel y. The purpose of this project is to detect human pulse through their fin ger. It provides variety of information such as their healthy information.

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