GB875631A - Improvements in or relating to electronic amplifiers - Google Patents

Abstract

875,631. Transistor amplifier circuits. PYE Ltd. Oct. 13, 1958 [Oct. 14, 1957], No. 32032/57. Class 40(6) A transistor amplifier connected in common emitter configuration has the emitter connected through one winding of a transformer to one side of the supply source and the collector electrode connected directly to the chassis and the other pole of the supply source the input signal being applied between the base and emitter electrodes. The transistor preferably has a metal body forming the connection to the collector and is both heat and electrically connected to the amplifier chassis thus providing a heat sink. Fig. 1 shows a power output stage of an audio frequency amplifier with the input signal being applied via transformer T1 between the emitter and base electrodes of the junction transistor TR, which is of the PNP type. The transistor is connected in a metal casing electrically connected to the collector which is directly connected to the chassis of the amplifier and to the negative side of power supply P. A D.C. blocking capacitor C is connected between the secondary winding of the transformer and the emitter electrode. Fig. 2 shows a multi stage amplifier comprising a driving stage and power amplifying stage with transistors TR1, TR2 respectively. The stages are connected in common emitter configuration and D.C. blocking condensers Cl, C2 are connected between the respective base and emitter electrodes and should be mounted to ensure low capacity between the body of the capacitors and the chassis to avoid attenuation at high frequencies. The collectors connected to the metal casing of the transistors are themselves collected directly to the chassis as is also the negative side of the power supply P. The amplifier may incorporate means for adjusting the overall response or feedback such as special impedances between the base and collector of one or more stages and a stabilizing network consisting of a shunt connected resistor capacitor may be arranged in series with one or more of the emitter connections. The amplifier may be of the push-pull type and NPN transistors may be used.