Correcting for Nonlinearity in a Photodetector

Abstract

Simple positive-feedback circuit varies bias voltage as necessary. Ideal detector biased with constant voltage, detector current proportional to photon flux plus constant offset. Detector connected between inverting input and ground, and feedback from operational amplifier through feedback resistor Rf make voltage at inverting input equal to noninverting input. Bias voltage held constant. Principle applied to linearizing mercury cadmium telluride infrared detectors in Fourier-transform spectrometers and other spectral and imaging instruments.