Question

Consider a transistor with AC current gain = 0.98, this transistor is first used as common base amplifier and then as common emitter amplifier. Then ratio of power gain in the two arrangements shall be (Given $\frac{R_{out}}{R_{in}}$ is same in both cases)

• A. 1:2500
  
• B. 1:500
  
• C. 500:1
• D. 2500:1

Answer 1

The correct option is A 1:2500

given $AC$ current given $\alpha =0.98$ then $CE$ current given $\beta =\frac{\alpha }{1-\alpha }=\frac{0.98}{0.02}=49$

In $C-B$ configuration power given $={\alpha }^2\frac{Rout}{Rin}$

and in $CE-$configuration, power given $={\beta }^2\frac{Rout}{Rin}$

on $\frac{Rout}{Rin}$ in same for both cases. Ratio $=\frac{{\alpha }^2}{{\beta }^2}=\frac{(0.98{)}^2}{(49{)}^2}=\frac{1}{2500}$