| 摘要 |
PURPOSE:To achieve high temperature stability and small sized circuit, by comparing an output of a feedback amplifier, which is the sum of a double base to emitter voltage and an offset voltage, with a double base to emitter voltage as a reference voltage. CONSTITUTION:An output voltage Vout10 of a feed back amplifier consisting of transistors (TRs) Q1-Q4 in which an output bias voltage at no signal taking a photo diode PD output current as an input is the sum between double base to emitter voltage drop VBE and an offset voltage Vp, is inputted to one output of a comparator CM. A voltage of 2VBE produced with TRs Q6, Q7 of diode connection and a resistor RC6 is inputted to another input as a reference voltage VR. Thus, even if the output bias voltage Vout13 of a feedback amplifier is lowered because of temperature change, since control is made so that the reference voltage VR is also lowered in following to it, correct comparison is made and an ouput 12 is obtained. |
