Abstract: Correction circuits for a projection television of the type having three picture tubes arranged side by side on a horizontal axis are disclosed. The picture tubes separately display red, green and blue information of a color television picture. A separate projection lens is provided adjacent the face plate of each picture tube for projecting superposed images on a remote screen. Each of the picture tubes is provided with a main deflection yoke for deflecting the generated cathode ray beam of that tube to generate picture images in the usual manner. In addition, each of the picture tubes is provided with a pre-deflection yoke which is driven by one or more correction circuits. These correction circuits, in combination with the pre-deflection yoke, provide scan compensation fields in the paths of the electron beams to provide convergence and raster distortion corrections in the optically projected images.

Abstract: A biasing circuit for a complementary symmetry transistor amplifier utilizing a control transistor is disclosed in which the base terminal of the control transistor is connected to the base terminal of one of the complementary transistors so that the bias current drawn by the amplifier transistors is the control current for the control transistor. A bias voltage establishing network includes one element connected between the emitter and collector terminals of the control transistor so that the bias voltage is coupled via the emitter-base junction of the control transistor to the complementary transistors and thus the bias current drawn by the complementary symmetry amplifier determines the degree of conduction of the control transistor and therefore the bias voltage applied to the amplifier. In this manner sufficient bias voltage is applied to the amplifier to maintain conduction to avoid crossover distortion and at the same time the current drawn by the amplifier is limited to prevent thermal runaway.