PURPOSE: To cope with discharge as well as suction by setting a ratio of input and output currents of a first and second current mirrors to 2 and obtaining an output current from the first or second, current mirror.

CONSTITUTION: The same constitution as the series circuit of a first transistor TR 1 and a first resistance 2 is given to the input side of a first current mirror 5. The ratio of the input current of the current mirror 5 and the output current of a current mirror 6 is defined as 2 to equalize the current flowing to the first TR 1 and that flowing to the current mirror 5. Thus, the voltage applied to both ends of a second resistance 4 is equal to the value of an input voltage source 3, and the current flowing to the current mirror 5 has the value obtained by dividing the input voltage by the resistance value of the second resistance 4. Since the converted output current can be taken out from either the first current mirror 5 or the second current mirror 6, this circuit can cope with discharge as well as suction.