Hybrid Parameters

The hybrid parameters represent a mixed or hybrid relationship between the voltages and currents in the two-port network.

And the voltage-current equations can be written as,

$\left( \begin{array}{l} {V_1}\\ {I_2} \end{array} \right) = \left( {\begin{array}{*{20}{c}} {{h_{11}}}&{{h_{12}}}\\ {{h_{21}}}&{{h_{22}}} \end{array}} \right)\left( \begin{array}{l} {I_1}\\ {V_2} \end{array} \right)$

or,

${V_1} = {h_{11}}{I_1} + {h_{12}}{V_2}$

${I_2} = {h_{21}}{I_1} + {h_{22}}{V_2}$

The parameters ${h_{11}},{h_{12}},{h_{21}},{h_{22}}$ can be defined as,

${h_{11}} = \frac{{{V_1}}}{{{I_1}}};\left[ {{V_2} = 0} \right]$=Short Circuit Impedance at port-1

${h_{12}} = \frac{{{V_1}}}{{{V_2}}};\left[ {{I_1} = 0} \right]$=Open Circuit Reverse Voltage Gain

${h_{21}} = \frac{{{I_2}}}{{{I_1}}};\left[ {{V_2} = 0} \right]$=Short Circuit Current Gain

${h_{22}} = \frac{{{I_2}}}{{{V_2}}};\left[ {{I_1} = 0} \right]$=Open Circuit Output Admittance

The hybrid parameter would find wide usage in electronic circuits, especially in constructing models for transistors. The parameter of transistor cannot be measured ether by short circuit admittance or by open circuit impedance measurement alone.

Equivalent network of hybrid parameters: