PURPOSE: To reduce the input impedance, to improve the common mode rejection ratio and the broad band current voltage conversion characteristic and DC characteristic by providing two common base transistors(TRs) provided to an input stage and a differential amplifier amplifying a voltage difference of a collector resistor.

CONSTITUTION: Two common base TRs Q1, Q2 provided to an input stage, two sets of resistors R7, R8 connected in series with collectors of the two TRs Q1, Q2, a differential amplifier A3 amplifying the voltage difference of the two sets of the resistors and a feedback resistor R9 connected between an output of the differential amplifier A3 and the emitter of the TR Q2 are provided to the conversion circuit. Thus, a current signal of a charge storage type photoelectric converter is converted into a voltage by the two common base TRs Q1, Q2 and the two sets of resistors R7, R8 at the input stage and the voltage difference of the two resistors is amplified by the differential amplifier. Thus, the input impedance is low, the common mode rejection ratio is improved, the broad band current voltage conversion characteristic is attained and the DC characteristic is improved.