Help me understand the solution of a simple voltage gain problem

[devnarayan]

in given fig. each network have voltage gain 1/2 then voltage gain of cascaded is (a)1/4 (b) 1/5 (c)1/6 (d)1 select correct option. answer provided is 1/5 ,any one can explain how 1/5 is correct

 

[keith1200rs]

Re: solve simple problem

The second network puts 2 ohms across the 1 ohm of the first network. So the effective load of the first network is 2/3 ohms. So, the voltage out of the first network is (2/3)/(1+2/3) of the input = 2/5. The output I half that = 1/5.

Keith

 

[devnarayan]

Re: solve simple problem

sir why you not directly apply the gain concept since gain of individual network is 1/2 so gain of overall becomes 1/4.

 

[keith1200rs]

Re: solve simple problem

Because the second network loads the first and therefore affects the gain (attenuation). If you put a unity gain buffer between the two networks the answer would be 1/4 like you expect.

Keith

 

[devnarayan]

Re: solve simple problem

respected sir , i am from India many many thanku for helping me. sir i have two problems which i found when write bsnl jto exam for telecom officer which confused me. these are
1. δ(-t-t0)*x(t0-t), = ?(where * stands for convolution ) option wasa) x(2to-t) (b)x(t) (c)x(-t) (d)x(t-2to)
2.select correct option
A transfer function is called minimum phase if
(a)if all it's are in left half plane
(b)if all the zeros in right half plane
(c)if all the poles and zeros are in the same half plane
(d)none of the above
sir, while i know that for minimum phase t.f all poles and zeros should in left side of s-plane but how answer this question. answer provided is answer 'b'
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