A Transistor Video Amplifier Having 80 Volts Output

A transistor video amplifier which has sufficient output signal, swing, and bandwidth to drive a standard picture tube is described. The amplifier consists of three junction transistors in the following configurations (starting at the input end): grounded-collector, grounded-emitter, and common-base. A resistive feedback path is provided from the output of the grounded-emitter stage to the amplifier input. Adequate dynamic range is obtained by means of the common-base stage which gives an output voltage swing that is twice the breakdown voltage of the transistor. The feedback employed not only improves the linearity and high-frequency response but also aids in obtaining d-c restoration. Because of the current and voltage variable reactance effects in junction transistors, the frequency response of the amplifier is a function of the operating point. Circuit models that are used in the analysis and design of such amplifiers are discussed.