Receiver circuit
A receiver circuit includes a photodiode, a first amplifier to convert a current of the photodiode into a voltage, a second amplifier to adjust an offset voltage of the first amplifier and a control unit to control on/off of an offset voltage adjustment function of the second amplifier. The control unit turns off the offset voltage adjustment function of the second amplifier in a predetermined period after power on.
1 . A receiver circuit comprising:
a photodiode;
a first amplifier to convert a current of the photodiode into a voltage;
a second amplifier to adjust an offset voltage of the first amplifier; and
a switching device connected between the first amplifier and the second amplifier.
2 . The receiver circuit according to claim 1 , wherein the receiver circuit further comprises:
a control circuit to control on/off of the switching device according to power supply potential.
3 . A receiver circuit comprising:
a photodiode;
a first amplifier to convert a current of the photodiode into a voltage;
a second amplifier to adjust an offset voltage of the first amplifier; and
a control unit to control on/off of an offset voltage adjustment function of the second amplifier,
wherein the control unit turns off the offset voltage adjustment function of the second amplifier in a predetermined period after power on.
4 . The receiver circuit according to claim 3 , wherein the control unit comprises:
a first transistor connected between a noninverting input terminal of the second amplifier supplied with a reference voltage and a noninverting input terminal of the first amplifier;
a second transistor connected between an output terminal of the second amplifier and the noninverting input terminal of the first amplifier; and
a control circuit to control on/off of the first and the second transistors.
5 . The receiver circuit according to claim 4 , wherein the control circuit turns on the first transistor and turns off the second transistor at power on and after a predetermined period, the control circuit turns off the first transistor and turns on the second transistor.
6 . The receiver circuit according to claim 3 , wherein the first amplifier has a wider band characteristic than the second amplifier.
7 . The receiver circuit according to claim 3 , wherein the second amplifier has a smaller input offset voltage than the first amplifier.
8 . The receiver circuit according to claim 3 , wherein the first and the second amplifiers include a plurality of transistors and a gate length and/or a gate width of the transistors included in the first amplifier is smaller than a gate length and/or a gate width of the transistors included in the second amplifier.