A Study of Transistor Circuits for Television

Abstract

This paper describes a general study of transistors in television receivers. For this purpose the development of a completely transistorized television receiver was undertaken. An experimental model using 37 developmental transistors and a five-inch kinescope housed in a cabinet 13×12×7 inches was constructed. This portable receiver operates on a single channel using a self-contained loop, and has a total battery-power consumption of 13 watts, more than 25 per cent of which is consumed by the kinescope heater. The development of a complete experimental receiver, even with a number of compromises, provided an opportunity to deal with the problems found in every stage and circuit of the receiver. Although experimental point-contact transistors have recently been developed which will provide oscillations for the entire vhf television band, considerable difficulty was found in providing wide-band rf gain using transistors at these frequencies. This problem was much less difficult at intermediate frequencies and at the intercarrier-sound frequency. The second-detector problem of obtaining high rectification efficiency with low load impedances was solved by using a transistor detector. The video amplifier problem was complicated by the requirement for a high input impedance; however, with a combination of junction and contact transistors a stable, high-gain video amplifier with a relatively high input impedance was built. An audio system using complementary symmetrical junction transistors was designed to produce high output with good efficiency. In the synchronization and deflection portion of the receiver, circuits were devised for using transistors in ways that differ from the analogues of vacuum tubes.