Noise adaptive IR receiver circuit - passes signal from detector diode biassing resistor over RC circuit to switching transistor and amplifier

摘要

The IR receiver may be used for remote control of TV or radio receivers. The diode is connected to the receiver input through suitable series resistors. The resistance change of the diode, due to the incident i.e. light, is amplified and applied to further amplifying and/or evauating devices. Amplifier gain is controlled as a function of interference light falling on the diode, and this of noise. The input signal for an additional circuit (T1-T4, R17-R19, C4) is taken from one of the diodes (D) series resistors (R2) and applied through a filter (R17, C4) to a switching transistor (T1). The output of tis transistor is connected to the amplifier (V) through a high value resistors (T2-T4). The threshold level of the amplifier is increased when the optical noise level increases.