sh 1 sh 2 sh 3 sh 4 sh n intervene between the switching devices sw 1 sw 2 sw 3 sw 4 sw n and the light emitting devices oel 1 oel 2 oel 3 oel 4 oel n respectively the sample and hold circuits sh 1 sh 2 sh 3 sh 4 sh n have capacitors c 1 c 2 c 3 c 4 c n respectively that are connected to sample and hold switching devices whose gates are connected to a common line so the gate of each sample and hold switching device switches on or off at a predetermined interval in synchronism with the rotation of the photosensitive drum another electrode of each of the capacitors c 1 c 2 c 3 c 4 c n is set to the ground or a given dc bias voltage v g the dc bias voltage v g can be changed in view of the external temperature and the life fig5 is a pulse sequence diagram for driving the active matrix circuit shown in fig4 pulse sequences having voltages in response to image signals are applied to the source lines i 1 and i 2 in synchronism with gate on pulses for the gate lines g 1 and g 2 the height of the pulse sequence for image signals reflects the gradation of the image density in a preferable embodiment the pulse width or the number of pulses can be changed in response to the gradation of the image density gate on pulses are applied to the connecting line so in order to switch on the gates of the sample and hold switching devices so that charges held in.