| 摘要 |
PURPOSE:To reduce the effect of external light or noise by providing a resonance circuit in parallel to a photodiode in an alternating manner. CONSTITUTION:A parallel resonance circuit 2 is connected to a photodiode 1 generating charge corresponding to the quantity of incident light in parallel in an alternating manner. An AGC amplifying circuit 6 for amplifying a signal is coupled with the circuit 2 by a coupling condenser 4 and a mu-factor is controlled by a mu-factor control terminal 7. The output of the circuit 6 is detected by a detection circuit 8 and compared with reference potential 10 by a comparing circuit 9 to be amplified to limit amplitude. A demodulation circuit 11 removes a carrier waveform from the output of the circuit 9 to demodulate the original signal data and outputs said signal data to an output terminal 12. Since a power supply condenser 5 is shortcircuited in an alternating manner, the diode 1 and the circuit 2 are connected in parallel in an alternating manner and has constitution wherein one terminal is earthed and a signal is generated at the other terminal by incident light. By this method, the signal only of objective light can be inputted to and after the amplifying circuit. |
