IMAGE PICKUP APPARATUS

Solid-state image pickup apparatus, such as an MOS imager, has a two-dimensional array of picture element units each formed of a photo sensitive element and a gating element, and scanning circuits for supplying horizontal and vertical scanning pulses. The picture unit elements in turn discharge a signal charge onto vertical and horizontal transmitting lines in response to the vertical and horizontal scanning pulses. Then, a resulting signal current is used to develop an output video signal. In order to provide a strong output video signal with a good S/N ratio, a current mirror circuit, formed of an input transistor and an output transistor with first current-carrying electrodes joined together to a voltage reference point and with control electrodes joined together, amplifies the signal current. A second current-carrying electrode of the input transistor receives a constant current from a current source and also receives the signal current. The output transistor has a second current-carrying electrode connected to an output load. Another current source can be connected to the output transistor so that only AC current will flow to the output load. The output load can be a load capacitor associated with a pre-charging transistor, or can be a serial charge transfer device.