Abstract: A light receiving circuit according to the present invention includes a current control voltage generation circuit 10 outputting control voltages Vcont1 and Vcont2, a first current adjusting circuit 11 generating a first output current Io1 by regulating a first input current Ii1 depending on a voltage difference of the control voltages Vcont1 and Vcont2, the first input current Ii1 generated by adding a first reference current Ia1 and an input current Ipd, a second current adjusting circuit 12 generating a second output current Io2 by regulating a second reference current Ia2 depending on the voltage difference of the control voltages Vcont1 and Vcont2, and a current voltage conversion circuit 13 generating a first output voltage Vo1 by converting the first output current Io1 to voltage based on a first resistance Rf1 and generating a second output voltage Vo2 by converting the second output current Io2 to voltage based on a second resistance Rf2.

Abstract: A light receiving circuit according to the present invention includes a current control voltage generation circuit 10 outputting control voltages Vcont1 and Vcont2, a first current adjusting circuit 11 generating a first output current Io1 by regulating a first input current Ii1 depending on a voltage difference of the control voltages Vcont1 and Vcont2, the first input current Ii1 generated by adding a first reference current Ia1 and an input current Ipd, a second current adjusting circuit 12 generating a second output current Io2 by regulating a second reference current Ia2 depending on the voltage difference of the control voltages Vcont1 and Vcont2, and a current voltage conversion circuit 13 generating a first output voltage Vo1 by converting the first output current Io1 to voltage based on a first resistance Rf1 and generating a second output voltage Vo2 by converting the second output current Io2 to voltage based on a second resistance Rf2.

Abstract: An oscillation circuit has a free-running oscillator operating at a predetermined frequency. A signal generator generates a trigger signal in synchronism with an input signal. The trigger signal is supplied to the free-running oscillator to bring the signal level in the oscillator to a reference level. The oscillator keeps its frequency even when there is no input signal, the frequency being approximately equal to an integer multiplied by the frequency of the input signal.

Abstract: The present invention provides a transistor circuit suited for a synchronizing signal separator. More particularly, the transistor circuit can separate the noise-free synchronizing signal from a composite video signal.The transistor circuit comprises a transistor having an emitter coupled to an input terminal through a capacitor and to a constant current source, a base applied with a bias voltage and a collector connected to an output terminal, a comparator comparing the emitter voltage with a reference voltage, and means for turning the transistor off in response to the comparator output. A current charging circuit is preferably added.