A transistor has hie =2k?, hoe=25µmhos and hfe=60 with an unbypassed emitter resistor Re=1k?. What will be the input resistance and output resistance?
A)90k? and 50k? respectively
B)33k? and 45k? respectively
C)6k? and 40k? respectively
D)63k? and 40k? respectively

Question

Quizplus · Accepted Answer

The input resistance $R_{in}$ of a transistor with an unbypassed emitter resistor $Re$ can be calculated using the formula $R_{in} = h_{ie} + (h_{fe} + 1)Re$. Substituting the given values, $R_{in} = 2000 + (60 + 1) \times 1000 = 2000 + 61000 = 63000\Omega$ or 63k$\Omega$.The output resistance $R_{out}$ can be calculated using the formula $R_{out} = \frac{1}{h_{oe} + \frac{1}{(Re + R_L)}}$, assuming $R_L$ (load resistance) is much larger than $Re$, the formula simplifies to $R_{out} = \frac{1}{h_{oe} + \frac{1}{Re}}$. Given $h_{oe} = 25\mu mhos = 25 \times 10^{-6} \Omega^{-1}$ and $Re = 1000\Omega$, $R_{out} = \frac{1}{25 \times 10^{-6} + \frac{1}{1000}} = \frac{1}{25 \times 10^{-6} + 0.001} = 40k\Omega$.

A Transistor Has Hie =2k?, Hoe=25µmhos and Hfe=60 with an Unbypassed