# Electronic Devices and Circuits Questions and Answers – The Common Collector Configuration

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This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “The Common Collector Configuration”.

1. The current amplification factor ϒdc is given by_________
a) IE/IB
b) IB/IE
c) IC/IE
d) IE/IC

Explanation: When no signal is applied, then the ratio of emitter current to base current is called as ϒdc of the transistor. As the collector is common to both input and output circuits, hence the name common collector configuration.

2. The relation between α and β is given by _________
a) 1/(1-α)=1- β
b) 1/(1+α)=1+ β
c) 1/(1-α)=1+ β
d) 1/(1+α)=1- β

Explanation: The current amplification factor (β) is given by IC//IB. When no signal is applied, then the ratio of collector current to the base current is called current amplification factor of a transistor. β is an ac base amplification factor. α is called as current amplification factor. The relation of IC and IB change as IC= βIB+ (1+ β) ICBO.

3. The CC configuration has an input resistance_________
a) 500kΩ
b) 750kΩ
c) 600kΩ
d) 400kΩ

Explanation: It has a high input resistance and very low output resistance so the voltage gain is always less one. It is used for driving a low impedance load from a high impedance source.

4. The application of a CC configured transistor is_________
a) voltage multiplier
b) level shifter
c) rectification
d) impedance matching

Explanation: The most important use of CC transistor is an impedance matching device. It is seldom used for amplification purposes. The current gain is same as that of CE configured transistor.

5. What is the output resistance of CC transistor?
a) 25 Ω
b) 50 Ω
c) 100 Ω
d) 150 Ω

Explanation: The CC transistor has a very low value of output resistance of 25 Ω. The voltage gain is always less one. It is used for driving a low impedance load from a high impedance source.

6. Increase in collector emitter voltage from 5V to 8V causes increase in collector current from 5mA to 5.3mA. Determine the dynamic output resistance.
a) 20kΩ
b) 10kΩ
c) 50kΩ
d) 60kΩ

Explanation: ro=∆VCE/∆IC
=3/0.3m=10kΩ.

7. A change in 300mV in base emitter voltage causes a change of 100µA in the base current. Determine the dynamic input resistance.
a) 20kΩ
b) 10kΩ
c) 30kΩ
d) 60kΩ

Explanation: ro=∆VBE/∆IB
=300m/100µ=30kΩ.

8. The point on the DC load line which is represented by ‘Q’ is called _________
a) cut off point
b) cut in point
c) breakdown point
d) operating point

Explanation: The point which represents the values of IC and VCE that exist in a transistor circuit when no signal is applied is called as operating point. This is also called as working point or quiescent point.

9. When is the transistor said to be saturated?
a) when VCE is very low
b) when VCE is very high
c) when VBE is very low
d) when VBE is very high

Explanation: When VCE is very low, the transistor said to be saturated and it operates in saturated region of characteristic. The change in base current IB does not produce a corresponding change in the collector voltage IC.

10. The input resistance is given by _________
a) ∆VCE/∆IB
b) ∆VBE/∆IB
c) ∆VBE/∆IC
d) ∆VBE/∆IE

Explanation: The ratio of change in base emitter voltage (∆VBE) to resulting change in base current (∆IB) at constant collector emitter voltage (VCE) is defined as input resistance. This is denoted by ri.

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

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