Photocell Amplifiers - Freecircuits.net
Electronic circuits schematics diagrams FreeCircuits.net [category-12.html] Photocell Amplifiers By internum Amplifiers for photoconductive, photodiode and photovoltaic cells. Amplifiers for photoconductive, photodiode and photovoltaic cells are shown in Figures 1, 2, 3 respectively. Figure 1. Amplifier for Photoconductive Cell All photogenerators display some voltage dependence of both speed and linearity. It is obvious that the current through a photoconductive cell will not display strict proportionality to incident light if the cell terminal voltage is allowed to vary with cell conductance. Somewhat less obvious is the fact that photodiode leakage and photovoltaic cell internal losses are also functions of terminal voltage. The current-to-voltage converter neatly sidesteps gross linearity problems by fixing a constant terminal voltage, zero in the case of photovoltaic cells and a fixed bias voltage in the case of photoconductors or photodiodes. Figure 2. Photodiode Amplifier Photodetector speed is optimized by operating into a fixed low load impedance. Currently available photovoltaic detectors show response times in the microsecond range at zero load impedance and photoconductors, even though slow, are materially faster at low load resistances. Figure 3. Photovoltaic Cell Amplifier The feedback resistance, R1, is dependent on cell sensitivity and should be chosen for either maximum dynamic range or for a desired scale factor. R2 is elective: in the case of photovoltaic cells or of photodiodes, it is not required in the case of photoconductive cells, it should be chosen to minimize bias current error over the operating range. 12 10 December 2007 See also: More Output Current Swing High Current Output Buffer with a pair of complementary transistors. Nonlinear Operational Amplifier Nonlinear Operational Amplifier with temperature-compensated breakpoints Summing Amplifier The summing amplifier, a special case of the inverting amplifier. Home Audio Video & TV Power RF Digital Computer Telephone Measurement Security Lights & LED Oscillators Op Amplifiers Other Search Copyright © 2007 freecircuits.net