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GATE 2023 EC – Question 46

Networks, Signals and Systems · Two-Port Networks and Wye-Delta Transformation · 2 marks · Multiple choice

The h-parameters of a two port network are shown below. The condition for the maximum small signal voltage gain $\dfrac{V_{out}}{V_s}$ is

Diagram for GATE 2023 EC question 46
  1. $h_{11}=0,\ h_{12}=0,\ h_{21}=$ very high and $h_{22}=0$
  2. $h_{11}=$ very high, $h_{12}=0,\ h_{21}=$ very high and $h_{22}=0$
  3. $h_{11}=0,\ h_{12}=$ very high, $h_{21}=$ very high and $h_{22}=0$
  4. $h_{11}=0,\ h_{12}=0,\ h_{21}=$ very high and $h_{22}=$ very high

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Correct answer: (A) $h_{11}=0,\ h_{12}=0,\ h_{21}=$ very high and $h_{22}=0$

Explanation

With the source connected, $V_1=V_s-h_{11}i_1$. The output is the load driven by the current source $h_{21}i_1$ in parallel with $1/h_{22}$. Gain is largest when the whole source voltage appears across the input ($h_{11}=0$), there is no reverse feedback ($h_{12}=0$), the current gain $h_{21}$ is high, and the output conductance $h_{22}=0$ so that all the current goes to $R_L$. That is option (A).