Question
Identify the features of CC configuration from the options given below.
The correct answer is
Highest input impedance and highest current gain.
The question asks to identify the characteristics of the Common Collector (CC) configuration, also known as the emitter follower.
CC Configuration Key Features
- Input Impedance ($Z_{in}$): The CC configuration offers a very high input impedance. This is primarily because the input signal drives the base-emitter junction, which has a high dynamic resistance, amplified by the transistor's current gain.
- Voltage Gain ($A_v$): The voltage gain is approximately unity ($A_v \approx 1$), slightly less than 1. It acts as a voltage follower, meaning the output voltage closely mimics the input voltage.
- Current Gain ($A_i$): The CC configuration provides a high current gain. The current gain is typically close to $\beta + 1$, where $\beta$ is the common-emitter current gain.
Analysis of Options
Based on the features:
- Option 1 correctly states highest input impedance and highest current gain.
- Option 2 is incorrect because while input impedance is high, the voltage gain is approximately 1, not the highest.
- Option 3 is incorrect because the input impedance is high, not low.
- Option 4 is incorrect; it describes characteristics more aligned with Common Base (low $Z_{in}$) or Common Emitter (high $A_v$) configurations.
Therefore, the defining features of the CC configuration are its high input impedance and high current gain.
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Important Questions from Configuration of BJT
BC147 is the transistor used for:
- What is the relationship between the common-emitter current gain ($\beta$) and the common-base current gain ($\alpha$) of a bipolar junction transistor (BJT)?
Which of the following is NOT true for a common collector transistor?
The other name for the common collector amplifier is -
Match List I with List II:
List I
(Bias Configuration of BJT)
List II
(Stability factor equation)
(A) Fixed Bias Configuration (I) S(V BE ) = \(\rm −\frac{\beta/R_E}{\beta+R_{TH}/R_E}\) (B) Emitter Bias Configuration (II) S(V BE ) = −β/R E (C) Voltage Divider Configuration (III) S(V BE ) = \(\rm −\frac{\beta/R_C}{\beta+R_E/R_C}\) (D) Feedback Bias Configuration (IV) S(V BE ) = \(\rm −\frac{\beta/R_E}{\beta+R_B/R_E}\) Choose the correct answer from the options given below :
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