# Electronic Devices and Circuits Questions and Answers – Cascading Transistor Amplifiers

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Cascading Transistor Amplifiers”.

a) High gain and high bandwidth
b) High gain and low bandwidth
c) Low gain and high bandwidth
d) Low gain and low bandwidth

Explanation: A circuit having a single transistor amplifier does not provide suitable bandwidth or gain. To overcome this difficulty, we combine several amplification stages. The cascading transistor amplifier theory is used for high gain as well as high bandwidth.

2. What is the advantage of using CB amplifier configuration in a cascading transistor amplifier?
a) High efficiency
b) Low distortion
c) Good high frequency operation
d) Good low frequency operation

Explanation: The cascading transistor amplifier circuit can be constructed with two configurations of a transistor that is CE (common-emitter) and CB (common base). The CB (common base) configuration delivers a good high-frequency operation.

3. What is the total voltage gain of a cascading transistor amplifier if the gain of first stage is 4 and the gain of the second stage is 10?
a) 0.4
b) 4
c) 40
d) 2.5

Explanation: The total gain of a cascading transistor amplifier can be calculated by the formula given below. Where, AV = overall gain, AV1 = voltage gain of first stage and AV2 = voltage gain of second stage.
AV = AV1 × AV2 = 4 × 10 = 40

4. What is the total voltage gain of a cascading transistor amplifier if input of first stage is 10V and the output of the second stage is 25V?
a) 0.4
b) 4
c) 40
d) 2.5

Explanation: The total gain of a cascading transistor amplifier is the ration of the output of second stage amplifier to the input of first stage amplifier. Where, Voutput = 25V and Vinput = 10V.
AV = Voutput / Vinput = 25V / 10V = 2.5

5. What does cascading of two transistor amplifiers imply?
a) Output of first stage sent to input of second stage
b) Output of first stage sent to coupling device
c) Input of first stage sent to input of second stage
d) Not related

Explanation: In multi-stage amplifiers, the output of first stage is coupled to the input of second stage using a coupling device. The coupling devices is typically a capacitor or a transformer. Cascading is known as the process of combining two amplifier stages using a coupling device.
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6. How many methods of coupling are used for a cascading transistor amplifier?
a) 3
b) 4
c) 2
d) 5

Explanation: There are four types of coupling mechanisms used. They are Resistance-capacitance coupling, thermal coupling, impedance coupling and transformer coupling. Resistance-capacitance coupling is the most vastly used mechanism.

7. What is the total voltage gain of a cascading transistor amplifier if the gain of first stage is 14dB, gain of the second stage is 12dB and gain of third stage is 24dB?
a) 40dB
b) 50.32dB
c) 50dB
d) 40.32dB

Explanation: The total gain of a cascading transistor amplifier is the sum of the multiple stages when the gain is calculated is decibels. Given, AV1 = 14dB, AV2 = 12dB and AV3 = 24dB
AV = AV1 + AV2 + AV3 = 14dB + 12dB + 24dB = 50dB

8. The coupling device is essential for a cascading transistor amplifier.
a) True
b) False

Explanation: One of the main functions of the coupling device in a cascading transistor amplifier is to block the direct current from passing through to the input of next stage from the output of the first stage. Another function of the coupling device is to transfer the current from the output of first stage to the input of the second stage.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.