GATE 2018 EE – Question 29
In the two-port network shown, the $h_{11}$ parameter (where, $h_{11}=\frac{V_1}{I_1}$, when $V_2=0$) in ohms is ________ (up to 2 decimal places).
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Correct answer: 0.49 to 0.51
Explanation
The current source $2I_1$ is connected from the input node to the output node, so with $V_2=0$ the port current is $I_{in}=I_1+2I_1=3I_1$, where $I_1$ is the current in the first $1\ \Omega$ resistor. At the middle node, $I_1=\frac{V_B}{1}+\frac{V_B-0}{1}$, so $V_B=\frac{I_1}{2}$ and $V_1=I_1+V_B=1.5I_1$. Then $h_{11}=\frac{V_1}{I_{in}}=\frac{1.5I_1}{3I_1}=0.5\ \Omega$.