Question

The output resistance of a common emitter transistor amplifier, if the input resistance is $200\Omega (\alpha =0.98$and power gain is $5\times {10}^6$, is)

• A. $516k\Omega$
• B. $216k\Omega$
• C. $300k\Omega$
• D. $416k\Omega$

Answer 1

The correct option is D $416k\Omega$

We know that
Voltage gain, $△V=\beta \frac{R_0}{R_i}$
Also, $\beta =\frac{\alpha }{1-\alpha }=\frac{0.98}{1-0.98}=49$
$△V=\left(49\right)\left(\frac{R_0}{200}\right)$
Power gain $△P$
$=Currentgain\left(\beta \right)\times voltagegain\left(△V\right)$
$\Rightarrow 5\times {10}^6=49\times 49\times \frac{R_0}{200}$
$\Rightarrow R_0=\frac{5\times {10}^6\times 200}{49\times 49}=0.416\times {10}^6=416k\Omega$.