Level_detector_for_photodiode

Published:2009/7/24 4:16:00 Author:Jessie | From:SeekIC

Fig. 15-3 This photodiode level detector operates from a single -10-V supply and is suitable for MOS logic. The output changes state when the D1 current reaches 1μA. Even at this low current, the error contributed by the LM111 is less than 1%. Higher threshold currents can be obtained by reducing R1, R2, and R3 proportionally. At the switching point, the voltage across D1 is nearly zero, so the D1leakage current does not cause an error. The output switches between ground and -10 V, The circuit will operate with a 5-V supply by reducing the values of R1, R2, and R3. Circuit accuracy depends on supply regulation because the reference is derived from the supply. National Semiconductor, Linear Applications Handbook 1991, p. 130.



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