Negative Characteristic Measurements

Author: Leonard Krugman

The characteristics of the three basic negative-resistance connections are not generally supplied by the manufacturer. These, however, may be obtained by a point plot. This is not too arduous a task since the curves are reasonably linear and the changeover points are well defined. For most purposes it is sufficiently accurate to insert a sweep signal into the controlled electrode and observe the response on an oscilloscope. Figure 6-10 (A) illustrates the basic measuring circuit for this application when the transistor is in the emitter controlled connection. A typical resulting E_e - I_e characteristic is shown in Fig. 6-10 (B).

Fig. 6-10. (A) Basic measuring circuit for obtaining negative resistance characteristics. (B) Typical negative resistance characteristic

The measuring circuit is easily modified for application to the base or collector controlled type. The plotted curve is similar to those illustrated in Figs. 6-9 (A) and 6-9 (C).