# Electronic Devices and Circuits Questions and Answers – Simplified Calculations for the CC Configuration

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Simplified Calculations for the CC Configuration”.

1. How do we computethe current gain of a simplified CC amplifier model using hybrid parameters?
a) 1 + hoe
b) 1 – hoe
c) 1 + hfe
d) 1 – hfe

Explanation: The current gain of a simplified common collector (CC) amplifier can be expressed in terms of approximate hybrid parameters. The current gain hfe is the forward transfer characteristics. The current gain of a common collector amplifier is expressed as 1 + hfe.

2. How do we compute the input resistance of a simplified CC amplifier model using hybrid parameters?
a) hie – (1 + hfe) × RL
b) hie + (1 + hfe) × RL
c) hie – (1 + hfe) / RL
d) hie + (1 + hfe) / RL

Explanation: The input resistance of a simplified common collector (CC) amplifier can be expressed in terms of approximate hybrid parameters. The input resistance is hie + (1 + hfe) × RL where, hie and hfe are the input resistance and current gain of CE amplifier respectively and RL is the load resistance.

3. How do we compute the voltage gain of a simplified CC amplifier model using hybrid parameters?
a) 1 + hie × Ri
b) 1 – hie × Ri
c) 1 + hie / Ri
d) 1 – hie / Ri

Explanation: The voltage gain of as implified common collector (CC) amplifier can be expressed in terms of approximate hybrid parameters. The voltage gain is equal to 1 – hie / Ri where, Ri is equal to hie + (1 + hfe) × RL .

4. What is the value of voltage VB of a CC amplifier configuration if VCC = 12V, R1 = 5kΩ and R2 = 8kΩ?
a) 6.54V
b) 0.7V
c) 4.6V
d) 7.38V

Explanation: The voltage VB of a simplified common collector amplifier configuration can be calculated using VB = I × R2. Given, VCC = 12V and R1 = 5kΩ and R2 = 8kΩ:
I = VCC / R1 + R2 = 12 / (5 + 8) = 0.92mA
VB = I × R2 = 0.92mA × 8kΩ = 7.38V

5. How do we compute the base impedance of a simplified CC amplifier?
a) β × (Re – re‘)
b) β × (Re + re‘)
c) RB || β × (Re – re‘)
d) RB || β × (Re + re‘)

Explanation: The base impedance of a simplified common collector (CC) amplifier can be expressed in terms circuit resistor values. The base impedance is β × (Re + re‘) . Where β is the transistor amplifiers current gain, Re is the equivalent emitter resistance and re‘ is the alternating current resistance of the emitter-base diode.

6. How do we compute the input impedance of a simplified CC amplifier?
a) β × (Re – re‘)
b) β × (Re + re‘)
c) RB || β × (Re – re‘)
d) RB || β × (Re + re‘)

Explanation: The input impedance of a simplified common collector (CC) amplifier can be expressed in terms circuit resistor values. The base impedance is RB || β × (Re + re‘) . Where β is the transistor amplifiers current gain, Reis the equivalent emitter resistance, RB is the equivalent base resistance and re‘ is the alternating current resistance of the emitter-base diode.

7. How do we compute the output impedance of a simplified CC amplifier?
a) RE || (re‘ – (R1 || R2) / (β + 1))
b) RE || (re‘ – (R1 || R2) / (β – 1))
c) RE || (re‘ + (R1 || R2) / (β + 1))
d) RE || (re‘ + (R1 || R2) / (β – 1))

Explanation: The output impedance of a simplified common collector (CC) amplifier can be expressed in terms circuit resistor values. The base impedance is RE || (re‘ + (R1 || R2) / (β + 1)) . Where β is the transistor amplifiers current gain, Re is the equivalent emitter resistance and re‘ is the alternating current resistance of the emitter-base diode.

8. What is the voltage gain of a simplified CC configuration amplifier if RE = 25kΩ and re‘ = 12kΩ?
a) 0.68
b) 0.59
c) 0.48
d) 0.086

Explanation: The voltage gain AV of a simplified common collector amplifier configuration can be calculated using AV = RE / (RE + re‘) . Given, RE = 25kΩ and re‘ = 12kΩ:
AV = RE / (RE + re‘) = 25 / 25 + 12 = 25 / 37 = 0.675 ≈ 0.68

9. What is the approximate value of the voltage gain of a simplified CC amplifier configuration?
a) 1
b) β
c) ∞
d) 0

Explanation: The voltage gain of a simplified CC amplifier configuration is approximately equal to unity (AV ≈ 1) and its current gain, Ai is approximately equal to β(Ai ≈ β) which depends on the value of each individual transistors.

10. There is no collector resistance in a simplified CC amplifier configuration.
a) True
b) False

Explanation: The simplified common collector (CC) amplifier configuration does not have a collector resistance RC. The collector terminal of the bipolar junction transistor is common to both the input and output circuit terminals.

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

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