For highest power gain, one would use _______ configuration

Question

Examoogle · Accepted Answer

CE

Explanation: The Common Emitter (CE) configuration provides both significant voltage gain and significant current gain, resulting in the highest overall power gain among the three BJT configurations. While Common Base (CB) offers high voltage gain but unity current gain, and Common Collector (CC) offers high current gain but unity voltage gain, the CE configuration acts as the ideal choice for power amplification.

Working Principle: In the CE configuration, the emitter is common to both input and output circuits. Because the input signal is applied to the base-emitter junction (low resistance) and the output is taken from the collector-emitter junction (high resistance), the configuration provides a large transformation of resistance. This transformation, combined with high current gain ($\beta$), results in a power gain that is typically in the range of 30-50 dB.

Key Formulas: $A_p = A_v 	imes A_i$ — Total Power Gain defined as the product of Voltage Gain and Current Gain; $P_{gain(dB)} = 10 \log_{10} \left(\frac{P_{out}}{P_{in}}ight)$ — Power gain measured in decibels

Key Points: Common Emitter configuration is characterized by a 180-degree phase shift between input and output.; CE configuration provides medium input impedance and medium output impedance.; The power gain of CE is the product of current gain ($h_{fe}$) and voltage gain.; CB is often used for high-frequency applications despite lower power gain.

Advantages: Highest power gain among standard configurations; Provides a 180-degree phase inversion; Good balance of voltage and current amplification

Disadvantages: Poor high-frequency performance due to Miller effect; Input impedance varies significantly with load resistance

Applications: Audio frequency amplifiers; Voltage and current amplification stages in multistage amplifiers

Additional Info: Option B (CB) has very high voltage gain but its current gain is less than unity, limiting power gain.. Option A (CC/Emitter Follower) has high current gain but voltage gain is slightly less than unity, resulting in poor power gain relative to CE.. CE is the standard 'workhorse' amplifier configuration in analog electronics.

Answer: C is correct — The Common Emitter (CE) configuration provides the highest overall power gain because it offers both high current gain and high voltage gain.

Exam Tip: In competitive exams, remember the mnemonic: CE = Both (Good voltage/current), CB = Voltage (High voltage only), CC = Current (High current only/Buffer).

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