A driver apparatus for driving a plurality of aligned light emitting thyristors, wherein each light emitting thyristor including a first terminal, a second terminal, and a control terminal that causes the light emitting thyristor to turn on and off, the driver apparatus comprising: a common terminal, each light emitting thyristor being disposed at one of a first position where the first terminal is connected to a first potential and the second terminal is connected to the common terminal and a second position where the first terminal is connected to the common terminal and the second terminal is connected to a second potential; a first resistor connected between the first potential and the common terminal; a second resistor connected between the common terminal and the second potential, wherein the first resistor and the second resistor constitute a voltage divider that divides a difference between the first potential and the second potential; a first switch connected between a node and one of a control voltage (Vcl) and the first potential, the first switch being turned on and off by a control signal (DRVON-N); a second switch connected between the node and one of the second potential and the control voltage (Vcl), the second switch being turned on and off complementarily to the first switch by the control signal (DRVON-N); and a third switch connected at one of a third position where the switch is connected between the second potential and the common terminal and a fourth position where the switch is connected between the common terminal and the first potential, the third switch being turned on and off according to the potential on the node, wherein the first switch, the second switch, and the third switch serve as a constant current source. a common terminal, each light emitting thyristor being disposed at one of a first position where the first terminal is connected to a first potential and the second terminal is connected to the common terminal and a second position where the first terminal is connected to the common terminal and the second terminal is connected to a second potential; a first resistor connected between the first potential and the common terminal; a second resistor connected between the common terminal and the second potential, wherein the first resistor and the second resistor constitute a voltage divider that divides a difference between the first potential and the second potential; a first switch connected between a node and one of a control voltage (Vcl) and the first potential, the first switch being turned on and off by a control signal (DRVON-N); a second switch connected between the node and one of the second potential and the control voltage (Vcl), the second switch being turned on and off complementarily to the first switch by the control signal (DRVON-N); and a third switch connected at one of a third position where the switch is connected between the second potential and the common terminal and a fourth position where the switch is connected between the common terminal and the first potential, the third switch being turned on and off according to the potential on the node, wherein the first switch, the second switch, and the third switch serve as a constant current source.