Power-transistor switching circuits

Summary form only given. This paper is a report of an investigation which included measurements of relevant 2NG8 PNP-power-transistor parameters and the developmetlt of a method for the design of high-power switrhing circuits with good trigger sensitivity and dc stability over wide temperature ranges. These design techniques can similarly be used for NPN power transistors. The relevant parameters of the simplified dc equivalent circuit are found. The methods and results of the measurements of these parameters are presented, including their variation with temperature and current. This data enables the designer to design a flip-flop circuit for a particular bias condition with temperature considerations as follows. When the ambient temperature is raised, excessive thermal collector current will cause the emitter junction of the OFF transistor to inject carriers. This is a cumulative effect resulting in the OFF transistor turning ON. A means of compensating for this instability is to use a suitable base bias to keep the OFF emitter from injecting carriers. On the other hand, excessive compensating.bias results in a circuit that will not have a stable ON state.