Transistor Curve Tracer

50 EE October 1988 TRANSISTOR CURVE TRACER There exist many ways of testing transistors, but each of these has its limitations because only one parameter is tested at a time. The curve tracer presented here tests all major characteristics in one go by displaying a number of curves on an oscilloscope screen. One limitation of the tracer should be mentioned right from the start, however: in the version discussed here, it can only test n-p-n transistors. Background to transistor testing A simple o.k./faulty test of a transistor can be carried out by considering the device as consisting of two anti-series connected diodes (Fig. 1). This test, which can be carried out with the aid of an ohmmeter, is fine for an initial check, but fails to provide information on one of the most important transistor characteristics: the static forward current transfer ratio, hFE, also referred to as the current amplification. Most bipolar transistors have 3 ter- minals: base (B), emitter (E) and collec- ...