Abstract: A transistor amplifier circuit is arranged in a differential amplifier incorporated into a power amplifier output circuit having approximately unity voltage gain and capable of feeding high current and power outputs to a load in response to high level voltage inputs from a signal source. This same signal source may be connected to drive a plurality of different output circuits simultaneously. A decoupling diode is provided in series with the emitter of each of the transistors of the differential amplifier, these diodes having a reverse breakdown voltage which is of the order of twice the peak input voltage and the supply voltage such that in the event that a short should appear in the load or in the power amplifier being driven, the diodes will act to effectively decouple the output of the signal source from the short circuit, thereby preventing the signal source output from being loaded down and, as a result, distorted.

Abstract: A modular printed circuit board assembly has a plurality of printed circuit boards each of which is integrated with a separate heat sink to form a modular unit. Each such modular unit is removably supported in a housing on a separate pair of support tracks in the base and top cover of the housing, bottom edges of the printed circuit board and a runner formed on the edge of the heat sink riding in these tracks. Each of the heat sinks has a flange portion to which the associated printed circuit board is attached and on which elements such as power transistors which generate a substantial amount of heat are directly mounted. The main body portion of each heat sink has a plurality of fins in the form of longitudinal strips with longitudinal slots being formed between the fins.

Abstract: A plurality of similar power amplifier circuits are connected in parallel in the output of an amplifier between the amplifier's voltage amplifier circuit and the load. Each of these amplifier circuits has a similar ballasting resistor connected between its output and the load. The amplifier circuits have unity closed loop voltage gain. The value of the ballasting resistors is empirically chosen such that these resistors are capable of accommodating differences in the outputs of the amplifier circuits which may occur, such that the load is equally shared between the amplifier circuits.

Abstract: A power supply has both high and low voltage power sources connected to a common output terminal. A switching circuit is connected between the high voltage source and this terminal, the switching circuit being controlled by a control circuit. The control circuit operates in response to malfunction and temperature sensors when these sensors have outputs indicative of equipment operating conditions outside of predetermined ranges for each of the sensed parameters. When the control circuit is not being actuated by an output from one of the sensors, the switching circuit is actuated to connect the high voltage output to the output terminal. In the event, however, that one of the temperature or malfunction sensors senses a condition outside of range, the control circuit is actuated, thereby deactuating the switching circuit to remove the high voltage output from the output terminal, leaving low voltage output.