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

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

1. How do we compute the current gain of a simplified CB amplifier model using hybrid parameters?
a) -hfe / 1 + hfe
b) -hfe / 1 – hfe
c) hfe / 1 + hfe
d) hfe / 1 – hfe

Explanation: The current gain of a simplified common base (CB) 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 base amplifier is expressed as hfe / 1 + hfe.

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

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

3. How do we compute the voltage gain of a simplified CB amplifier model using hybrid parameters?
a) hfe × RL / hie
b) -hfe × RL / hie
c) hfe × RL / hoe
d) -hfe × RL / hoe

Explanation: The voltage gain of a simplified common base (CB) amplifier can be expressed in terms of approximate hybrid parameters. The voltage gain is equal to hfe × RL / hie where, RL is load resistance, hie is input resistance of CE amplifier and -hfe is the current gain of CE amplifier.

4. What is the value of voltage VB of a CB amplifier configuration if VCC = 12V, R1 = 25kΩ and R2 = 6kΩ?
a) 2.84V
b) 13.03V
c) 2.45V
d) 2.32V

Explanation: The voltage VB of a simplified common base amplifier configuration can be calculated using VB = I × R2. Given, VCC = 12V and R1 = 25kΩ and R2 = 6kΩ:
I = VCC / R1 + R2 = 12 / (25 + 6) = 0.387mA
VB = I × R2 = 0.387mA × 6kΩ = 2.32V

5. What is the bias of a simplified common base (CB) amplifier configuration?
a) Reverse biased
b) Forward biased
c) Forward and reverse biased
d) It is independent of the bias

Explanation: The common base design amplifier works to such an extent that the input signal is applied to the emitter terminal and the yield is taken from the collector terminal. The emitter current is likewise the input current, and the collector current is additionally the yield current. The base-emitter intersection is forward-biased.
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6. How do we compute the voltage gain of a simplified CB amplifier?
a) RB || re
b) RC || re
c) RB / re
d) RC / re

Explanation: The voltage gain of a simplified common base (CB) amplifier can be expressed in terms circuit resistor values. The base impedance is RC / re‘. Where RC is the equivalent current resistance and re‘ is the alternating current resistance of the emitter-base diode.

7. How do we compute the output impedance of a simplified CB amplifier?
a) RC + RL
b) RB + RL
c) RC || RL
d) RB || RL

Explanation: The output impedance of a simplified common base (CB) amplifier can be expressed in terms circuit resistor values. The base impedance is RC || RL. Where RC is the equivalent collector resistance and RL is the equivalent load resistance.

8. What is the value of β in a simplified CB configuration amplifier if IC = 124mA and IB = 1.26mA?
a) 98.41
b) 99.24
c) 100
d) 97.33

Explanation: The value of β in a simplified common base amplifier configuration can be calculated using β = IC / IB. Given, IC = 124mA and IB = 1.26mA:
β = IC / IB = 124 / 1.26 = 98.41

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

Explanation: The current gain of a simplified CB amplifier configuration is approximately equal to unity (Ai ≈ 1). Ai is approximately equal to β / β + 1. The value of β depends on the value of each individual transistors.

10. The simplified common base amplifier configuration is useful in audio and radio frequency applications.
a) True
b) False

Explanation: The common base amplifier plan is very helpful in sound and radio recurrence applications because of its input yield impedance attributes. The current buffer is utilized to coordinate a low-impedance source to a high-impedance.

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