H - Electricity – 04 – B
Patent
H - Electricity
04
B
325/1
H04B 10/06 (2006.01) H04B 10/158 (2006.01)
Patent
CA 2027410
ABSTRACT OF THE DISCLOSURE A case where a high bias voltage is required for a photo-element of a photo-receiver, a high voltage is applied to an amplifier which amplifies a photo-current created by the photo-element, when a power supply is turned on. In a prior art photo-receiver, the amplifier may be broken due to this high voltage. In the present invention, the photo-receiver is provided with a protection circuit comprising a diode connected between a power supply circuit and a photo-element, a resistor connected in parallel with the diode, and a first capacitor having one end thereof connected to an anode of the diode and the other end thereof connected to a reference potential. Constants of the circuit components are set such that a time constant of the supply of the power to the amplifier is smaller than a rising time constant of the supply of the power to the photo-element and larger than a falling time constant of the supply of the power to the photo-element. Accordingly, the supply of the power to the photo- element is started after the potential at the input terminal of the amplifier has been established and the potential at the input terminal of the amplifier floats after the supply of the power to the photo-element has been fully extinguished. As a result, the amplifier is not broken at the time of power-on and a surge voltage is not applied to the input terminal of the amplifier at the time of power-off.
Marks & Clerk
Sumitomo Electric Industries Ltd.
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