Question

1. a transistors current gain is equal to

a. collector current divided by emitter current.
b. emitter current divided by base current.
c. collector current divided by base current.
d. base current divided by collector current.

Explanation:

The current gain (\(\beta\)) of a transistor in common - emitter configuration is defined as the ratio of collector current (\(I_C\)) to base current (\(I_B\)). Mathematically, \(\beta=\frac{I_C}{I_B}\).

• Option A: \(\frac{I_C}{I_E}\) is the current transfer ratio (\(\alpha\)) where \(I_E = I_B+I_C\) and \(\alpha=\frac{I_C}{I_E}\lt1\), not the current gain.
• Option B: \(\frac{I_E}{I_B}=\frac{I_B + I_C}{I_B}=1+\beta

eq\beta\)

• Option C: \(\beta=\frac{I_C}{I_B}\), which is the correct formula for current gain.
• Option D: \(\frac{I_B}{I_C}=\frac{1}{\beta}

eq\beta\)

Answer:

C. collector current divided by base current.