- Fig. 4.28 shows the short circuit failures in a transistor. We shall discuss the circuit behaviour in each case.
(i) Collector-emitter short: Fig. 4.28 (i) shows a short between collector and emitter. The emitter diode is still forward biased, so we expect to see 0.7V at the base. Since the collector is shorted to the emitter, VC = VE = 0V.
(ii) Base -emitter short. Fig 4.28 (ii) shows a short between base and emitter. Since the base is now directly connected to ground, VB = 0. Therefore, the current through RB will be diverted to ground and there is no current to forward bias the emitter diode. As a result, the transistor will be cutoff and there is no collector current. So we will expect the collector voltage to be 12V.
(iii) Collector-base short: Fig. 4.28 (iii) shows a short between the collector and the base. In this case, the emitter diode is still forward biased so VB = 0.7V. Now, however, because the collector is shorted to the base, VC = VB = 0.7V.
Wilfykil answered the question on August 14, 2019 at 13:51
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