Patent ID: 7759978

Claim:
A current driver circuit comprising: a current output terminal from which current is output; a first transistor having one end connected to the current output terminal; a first sense resistor connected between the other end of the first transistor and the ground; an operational amplifier having an output connected to a first control electrode of the first transistor, having first and second input terminals, and outputting a signal to the first control electrode based on a voltage input to the first input terminal and a voltage input to the second input terminal; a polarity switching circuit having a first switching terminal to which a first contact voltage at a first contact between the first sense resistor and the first transistor is input and a second switching terminal to which a control voltage for controlling a current output from the current output terminal is input, capable of outputting the first contact voltage and the control voltage to the first and second input terminals, and capable of inverting the polarity of an amplified signal output from the operational amplifier; and a control circuit that outputs the control voltage obtained by adding an offset voltage of the operational amplifier between the first and second input terminals to a set voltage which is set in correspondence with value of a target output current, wherein in a case where potential of the first input terminal is lower than that of the second input terminal by an amount of the offset voltage, in a normal operation mode in which normal operation is performed, the control circuit controls the polarity switching circuit so as to input the first contact voltage of the first contact to the first input terminal and input the control voltage to the second input terminal and, on the other hand, in a case where the potential of the first input terminal is higher than that of the second input terminal by an amount of the offset voltage, in the normal operation mode, the control circuit controls the polarity switching circuit so as to input the first contact voltage at the first contact to the second input terminal, input the control voltage to the first input terminal, and invert the polarity of the amplified signal.