Re: Reverse engineering Lumenition optical switch
Phototransistors use the collector-base junction as the photodiode. Hit it with light and the transistor itself leaks current from its collector to its own base. This is the current that biases up the base and is amplified by the Hfe of the transistor.
The base connection is normally left floating. It's brought out so a filter capacitor could be added if needed, and so that the photo diode and transistor characteristics can be measured.
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
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