Silicon phototransistor vidicon

The use of silicon phototransistor arrays as high gain targets in vidicon camera tubes is shown to provide a sensitivity advantage. An analysis of device operating parameters indicates that signal enhancement can be obtained during both the write and read portions of an array element's duty cycle. Maximum effective signal amplification is secured by choosing a design which recharges the collector-base storage capacitance mostly during the read interval. Expressions for the effective signal gain in terms of transistor common base current gains and elemental capacitances have been derived, and the effects of phototransistor operation on vidicon sensitivity, image persistence, and dynamic range have been considered. Experimental transistor arrays have been fabricated and have been used for the first successful demonstration of phototransistor signal gain under the usual conditions of vidicon operation. Signal gains exceeding 70 have been recorded.