Test: BJT As an Amplifier -1 - Electronics and Communication Engineering (ECE) MCQ

As the load resistance is increases, collector current reduces and hence current gain (β) is decreased.

Since the short-circuit current gain h_fe of a common-emitter stage is much greater than unity, it is possible to increase the voltage amplification by cascading such stages. Hence, in a cascade, the intermediate transistors should be connected in a common-emitter configuration.

The common-collector transistor configuration is called the emitter follower because its voltage gain is close to unity (low) and hence the emitter follows the input signal.
Hence, assertion is a false statement.

The equivalent circuit of the given cascade amplifier can be drawn as shown below.

Figure below shows the small-signal circuit (with D.C. voltage source and capacitors short circuited).

The Darlington connection of three or more transistors is usually impractical because leakage current of the first transistor is amplified by the second due to which the overall leakage current may become high.
Reason is individually a correct statement. Hence, both assertion and reason are correct but reason is not the correct explanation of assertion.

The input resistance of emitter follower can be increased by bootstrapping the darlington circuit through the addition of capacitor C₀ between the first collector (C₁) and the second emitter (E₂).

h-parameters are real numbers upto radio frequency only. The smallest value of h-parameter is that of open circuit output admittance (h₀). Hence, statements 2 and 4 are not correct.