Question

A BJT has \(\beta=100\). If the base current is \(40\,\mu\mathrm{A}\), then the collector current is

• A. \(2\ \mathrm{mA}\)
• B. \(4\ \mathrm{mA}\)
• C. \(40\ \mathrm{mA}\)
• D. \(400\ \mathrm{mA}\)

Hint:

For a BJT, \[ \boxed{ I_C=\beta I_B } \] where \(\beta\) is the common-emitter current gain.

Answer 1

The Correct Option is B

Step 1: Use the current gain relation. For a BJT, \[ \beta=\frac{I_C}{I_B}. \] Hence, \[ I_C=\beta I_B. \] Given, \[ \beta=100, \] \[ I_B=40\,\mu\mathrm{A}. \]

Step 2: Calculate the collector current. \[ I_C = 100\times40\,\mu\mathrm{A} = 4000\,\mu\mathrm{A} = 4\,\mathrm{mA}. \] Hence, \[ \boxed{4\,\mathrm{mA}} \] Therefore, \[ \boxed{(B)} \] is the correct answer.