Circuitry suppressing DC component of current through photodetector - when photodetector is exposed to direct and alternating illumination uses two transistors

摘要

The output stage of a transistor (T2) is connected in series to the photo-detector (T1), and the control electrode of the transistor lies on a fixed potential and the control stage of the transistor has a capacitor (C) in parallel with it. The photodetector can be a photoelectric transistor without a base terminal, whose collector-emitter stage has the output stage of the transistor in parallel with it. The transistor can be a bipolar transistor or a field-effect transistor. The fixed potential at the control electrode of the transistor can be adjusted by a voltage divider (R1, R2).