In a transistor of common base connection, the ratio of change in the output current to change in the input cu

Question

In a transistor of common base connection, the ratio of change in the output current to change in the input current at a constant collector-base voltage is called ______.

Examoogle · Accepted Answer

The correct answer is Option C: current amplification factor. In a Common Base (CB) configuration of a Bipolar Junction Transistor, the ratio of change in collector current (output) to the change in emitter current (input) at a constant collector-base voltage is defined as the current amplification factor, denoted by $\alpha$. This parameter represents the efficiency with which the transistor transfers current from the input to the output.

Step-by-Step Solution & Concepts:
In a Common Base (CB) configuration of a Bipolar Junction Transistor, the ratio of change in collector current (output) to the change in emitter current (input) at a constant collector-base voltage is defined as the current amplification factor, denoted by $\alpha$. This parameter represents the efficiency with which the transistor transfers current from the input to the output.

Working Principle: The principle relies on the transport mechanism of charge carriers across the thin base region. Since the emitter current is the sum of the collector and base currents ($I_E = I_C + I_B$), and the collector current is proportional to the emitter current minus the base recombination current, the ratio $\alpha = \frac{\Delta I_C}{\Delta I_E}|_{V_{CB}}$ describes the fraction of emitter current that successfully reaches the collector.

Key Formulas: $\alpha_{dc} = \frac{I_C}{I_E}$ — DC Current Amplification Factor; $\alpha_{ac} = \left. \frac{\Delta I_C}{\Delta I_E} ight|_{V_{CB}} = 	ext{constant}$ — AC Current Amplification Factor

Key Points: The value of $\alpha$ is always less than unity, typically ranging from $0.95$ to $0.99$.; It is also known as the large-signal or small-signal current gain in the CB configuration.; The common base configuration provides high voltage gain but has a current gain of less than $1$.

Advantages: Excellent temperature stability compared to common emitter configuration; High input-to-output isolation due to base acting as a shield

Disadvantages: Low input impedance; Current gain is less than unity

Applications: High-frequency amplifiers; Impedance matching circuits

Additional Info: Option A (input resistance) is defined by $\frac{\Delta V_{EB}}{\Delta I_E}$.. Option B (output resistance) is defined by $\frac{\Delta V_{CB}}{\Delta I_C}$.. The parameter $\alpha$ is related to the common-emitter gain $\beta$ by the formula $\beta = \frac{\alpha}{1-\alpha}$.

Answer: C is correct — The ratio of change in collector current to the change in emitter current at constant collector-base voltage is the definition of the AC current amplification factor ($\alpha$).

Exam Tip: Always remember that in Common Base (CB), the gain $\alpha 1$.

Examoogle · Answer

Option A: input resistance factor

Examoogle · Answer

Option B: output resistance factor

Examoogle · Answer

Option D: base current amplification factor

Correct Answer

Solve 10,000+ More Questions with AI Tutor

Discussion (0)

Correct Answer

Solve 10,000+ More Questions with AI Tutor

Related Questions

Discussion (0)