The gain factor of an amplifier is increased from 10 to 12 as the load resistance is changed from 4 kΩ to 8 KΩ. Calculate (a) the amplification factor and (b) the plate resistance.

…(i)


where A is the voltage gain, μ is the amplification factor, RL is the load resistance and rp is the plate resistance


Given:


A1=10, Rl1 = 4kΩ


A2=12, Rl2 = 8kΩ


Putting these two values in equation (i)




We get a linear equation in 2 variables (rp and μ)



…(ii)


We will get another equation by substituting the values of A2 and Rl2 is equation (i)




… (iii)


Solving (ii) and (iii) to find the values amplification factor and the plate resistance.


&


From (ii)


…(iv)


Substituting (iv) in (iii)





Using μ =15, the value of rp is 2000Ω or 2 kΩ


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