In a common base amplifier circuit, calculate the change in...

In a common base amplifier circuit, calculate the change in base current if that in the collector current is $2 \mathrm{~mA}$ and $\alpha=0.98$.
(A) $980 \mathrm{~mA}$
(B) $2 \mathrm{~mA}$
(C) $0.04 \mathrm{~mA}$
(D) $1.96 \mathrm{~mA}$

Key Concepts

Bipolar Junction Transistor Current Relationships

This concept explains the fundamental relation I_E = I_C + I_B in bipolar junction transistors. It is crucial for understanding how variations in one terminal current (collector or emitter) affect the others, especially when analyzing changes or small signals in transistor circuits.

Common Base Amplifier Configuration

In the common base configuration, the base terminal is typically held at a constant potential, making the emitter the input and the collector the output. This setup emphasizes the relationship between the emitter and collector currents through the current gain alpha, vital for signal amplification analysis.

Current Gain (alpha) in BJTs

Alpha (?) is the common-base current gain defined as the ratio of the collector current to the emitter current (? = I_C/I_E). Since it is usually close to 1, small variations in the collector current result in even smaller base current changes, playing an important role in transistor performance and circuit stability.

Calculating Change in Base Current

This technique involves determining the emitter current change from the collector current change using the relation ?I_E = ?I_C/?, and then finding the base current change using ?I_B = ?I_E - ?I_C. This method is essential for small-signal analysis and understanding dynamic responses in transistor amplifier circuits.

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