Question

If the collector current changes from $2mA$ to $3mA$ in a transistor when collector - emitter voltage is increased from $2V$ to $10V$, the output resistance is

• A. $1K$$\Omega$
• B. $8K$$\Omega$
• C. $8m$$\Omega$
• D. $1m$$\Omega$

Answer 1

Answer: (B)

$8K$$\Omega$

Given that:
$\Delta I=I2-I1=3-2=1mA={10}^{-3}A$
$\Delta V=V2-V1=10-2=8V$
For transistors in CB mode, the dynamic resistance is the ratio of change in emitter voltage to the change in emitter current.
$r_d=\frac{\Delta V}{\Delta I}$

$r_d=\frac{8}{{10}^{-3}}=8000=8k\Omega$