Amorphous-silicon linear-array device technology; applications in electronic copying

For electronic-copying applications, amorphous silicon thin-film transistors (TFTs), photodiodes, and thin-film resistors are fabricated in a linear array on a glass substrate and mounted in an ionographic printing head. A document imaged on the array of photodiodes produces photocurrents which are amplified and converted to voltages on a corresponding array of output electrodes. These output electrodes are used to modulate the flow of ions exiting the printing head. This electronic copy function operates as a completely analog circuit, in that the output voltage (and therefore the modulation in ion current) is directly proportional to the light intensity impinging on each photodiode. The design and performance of this device are discussed