What is the value of the DC current gain in common collector configuration?

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ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 1
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  1. 1 + β 
  2. β
  3. α 
  4. 1 + α 

Answer (Detailed Solution Below)

Option 1 : 1 + β 
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Detailed Solution

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  • Common collector configuration, also known as emitter follower provides high input impedance and low output impedance. So they are used for the purpose of impedance matching.
  • In common collector configuration, the collector terminal is common to both input and output terminals.
  •  

    The DC current gain is therefore given by the ratio of emitter current to the base current, i.e.

    IE = Emitter Current

    IB = Base Current

    Also, IE = IB + IC

    DC current gain will be:

       ---(1)

    The DC current gain for a common emitter configuration is defined as:

    Equation (1) now becomes:

    Important Differences between different transistor configuration is as shown:

    Parameter

    Common-Base

    Common-Emitter

    Common-Collector

    Input Current

    IE

    IB

    IB

    Output Current

    IC

    IC

    IE

    Current Gain

        

    Voltage Gain

    Medium

    Medium

    Less Than 1

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