AUTOMATIC PHOTOCELL LOADING

摘要

-9- Case No. 4329 AUTOMATIC PHOTOCELL LOADING A circuit (10) that prevents a photo diode (12) from reaching its saturation output voltage thus ensuring the sensitivity of the photo diode to small changes in radiance at high radiance levels is disclosed. The circuit utilizes a transistor (30) that is allowed to conduct after the output voltage of the photo diode (12) has reached a predetermined level thus shunt loading the photo diode preventing it from reaching its saturation level. A resistor (28)capacitor (32) time constant circuit is provided preventing the transistor (30) from conducting until the output voltage of the photo diode (12) has reached a predetermined level for a predetermined period of time thus preventing premature conduction of the transistor (30) in response to transient or spurious voltages.