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Fig. 4.27 shows the open circuit failures in a transistor. What will be the circuit behaviour in each case ?

Fig. 4.27 shows the open circuit failures in a transistor. What will be the circuit behaviour in each case ?

Answers

Fig 4.27 shows the open circuit failures in a transistor. We shall discuss the circuit behaviour in each case.

(i) Open emitter: Fig. 4.27 (i) shows an open emitter failure in a transistor. Since the collector diode is not forward biased, it is OFF and there can be neither collector current nor base current.
Therefore, there will be no voltage drops across either resistor and the voltage at the base and at the collector leads of the transistor will be 12V.

(ii) Open-base: Fig. 4.27 (ii) shows an open base failure in a transistor. Since the base is open, there can be no base current so that the transistor is in cut-off. Therefore, all the transistor currents are 0A. In this case, the base and collector voltages will both be at 12V.
Note It may be noted that an open failure at either the base or emitter will produce similar results.

(iii) Open collector: Fig. 4.27 (iii) shows an open collector failure in a transistor. In this case, the emitter diode is still ON, so we expect to see 0.7V at the base. However, we will see 12V at the collector because there is no collector current.

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Wilfykil answered the question on August 14, 2019 at 13:46

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