A common emitter amplifier has a voltage gain of 50, an input impedance of 100 Ω and an output impedance of 200 Ω . The power gain of the amplifier is

Question

A common emitter amplifier has a voltage gain of 50, an input impedance of 100 Ω and an output impedance of 200 Ω . The power gain of the amplifier is, 500, 1000, 1250, 100

MARKS App · Accepted Answer

AC power gain = C h a n g e i n o u t p u t p o w e r C h a n g e i n i n p u t p o w e r = ∆ V c × ∆ i c ∆ V i × ∆ i b = ∆ V c ∆ V i × ∆ i c ∆ i b = A V × β A C where A V i s v o l t a g e g a i n and β A C is AC current gain. Also, A V = β A C × r e s i s t a n c e g a i n = R o R i Given, A V = 50 , R o = 200 Ω , R i = 100 Ω Hence, 50 = β A C × 200 100 ∴ β A C = 25 Now, AC power gain = A V × β A C = 50 × 25 = 1250

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