A drive circuit that compensates for the dispersion of the characteristics of drive transistors is disclosed. A switch SW2 is turned off, and switches SW1 and SW3 are turned on. Thereby, a constant current from a constant current source CC1 is flown in a drive transistor T1. Consequently, a gate voltage corresponding to the constant current Is written in the gate of the drive transistor T1. Then, the switches SW1 and SW3 are turned off, and the switch SW2 is turned on. Simultaneously, the voltage of a capacitor C1 on the side of the switch SW4 is varied according to a signal voltage, and thereby the voltage is added to the gate of the drive transistor T1 to flow a current corresponding to the signal voltage in the drive transistor T1.