The area of safe operation of transistors for switching operation

A thermal feedback model is presented for the analytical definition of the ASO (Area of Safe Operation) for transistors in switching operations. This area is narrowed by the "second breakdown in p-n junction," and the approximate representation of the breakdown threshold is presented. This model consists of a forward and feedback energy flow with gains A and B, respectively. . Therefore, the condition of the breakdown can be introduced as , where is the current multiplication factor, θ is transient thermal resistance, is a newly introduced current concentration factor, and αRis the temperature coefficient of Ie. Experimental results are also reported for a germanium alloy type transistor.