In ABCD parameters, A and C are called
![In ABCD parameters, A and C are called](http://storage.googleapis.com/tb-img/production/19/08/26%20June_1.png)
A. reverse current ratio and transfer admittance
B. reverse voltage ratio and transfer impedance
C. reverse current ratio and transfer impedance
D. reverse voltage ratio and transfer admittance
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
ABCD Parameters:
ABCD parameters relate the variables at the input port to those at the output port.
\(\left[ {\begin{array}{*{20}{c}} {{V_1}}\\ {{I_1}} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} A&B\\ C&D \end{array}} \right]\left[ {\begin{array}{*{20}{c}} {{V_2}}\\ { - {I_2}} \end{array}} \right]\)
V1 = AV2 - BI2
I1 = CV2 - DI2
With output open-circuited, i.e. I2 = 0, the two parameters we get are:
\(A = {\left. {\frac{{{V_1}}}{{{V_2}}}} \right|_{{I_2} = 0}}\)
A = Reverse voltage ratio, as it is the ratio of output voltage and the input voltage
\({\left. {C = \frac{{{I_1}}}{{{V_2}}}} \right|_{{I_2} = 0}}\)
C = Transfer admittance, as it is the ratio of current to the voltage
With the input short-circuited, i.e. V1 = 0, the two parameters we get are:
\({\left. {B = - \frac{{{V_1}}}{{{I_2}}}} \right|_{{V_2} = 0}}\)
\({\left. {D = \frac{{{I_1}}}{{{I_2}}}} \right|_{{V_i} = 0}}\)
Z-parameter are also known as the Open-Circuit impedance parameters as they are calculated under open-circuit conditions, i.e. at I1 = 0 and I2 = 0, In the matrix form, they are expressed as:
\(\left[ {\begin{array}{*{20}{c}} {{V_1}}\\ {{V_2}} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} {{z_{11}}}&{{z_{12}}}\\ {{z_{21}}}&{{z_{22}}} \end{array}} \right]\left[ {\begin{array}{*{20}{c}} {{I_1}}\\ {{I_2}} \end{array}} \right]\)
V1 = z11I1 + z12I2
V2 = z21I1 + z22I2
With the input open-circuited, i.e. I1 = 0, the two parameters obtained are:
\({z_{12}} = {\left. {\frac{{{V_1}}}{{{I_2}}}} \right|_{{I_1} = 0}}\)
\({z_{22}} = {\left. {\frac{{{V_2}}}{{{I_2}}}} \right|_{{I_1} = 0}}\)
With the output open-circuited, i.e. I2 = 0, the two parameters we obtain are:
\({z_{11}} = {\left. {\frac{{{V_1}}}{{{I_1}}}} \right|_{{I_2} = 0}}\)
\({z_{21}} = {\left. {\frac{{{V_2}}}{{{I_1}}}} \right|_{{I_2} = 0}}\)
Y (Admittance) Parameters:
They are also called the short circuit parameters, as they are calculated under short circuit conditions, i.e. at V1 = 0 and V2 = 0.
Expressed in Matrix Form as:
\(\left[ {\begin{array}{*{20}{c}} {{I_1}}\\ {{I_2}} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} {{Y_{11}}}&{{Y_{12}}}\\ {{Y_{21}}}&{{Y_{22}}} \end{array}} \right]\left[ {\begin{array}{*{20}{c}} {{V_1}}\\ {{V_2}} \end{array}} \right]\)
I1 = Y11V1 + Y12V2
I2 = Y21V1 + Y22V2
With the output short-circuited, i.e. V2 = 0, the two parameters obtained are:
\({Y_{11}} = {\left. {\frac{{{I_1}}}{{{V_1}}}} \right|_{{V_2} = 0}}\)
\({Y_{21}} = {\left. {\frac{{{I_2}}}{{{V_1}}}} \right|_{{V_2} = 0}}\)
With the input short-circuited, i.e. V1 = 0, the two parameters obtained are:
\({Y_{12}} = {\left. {\frac{{{I_1}}}{{{V_2}}}} \right|_{{V_1} = 0}}\)
\({Y_{22}} = {\left. {\frac{{{I_2}}}{{{V_2}}}} \right|_{{V_1} = 0}}\)
Hybrid parameters:
They represent the relationship between the voltage and the current in a two-port network and are expressed in the matrix form as:
\(\left[ {\begin{array}{*{20}{c}} {{V_1}}\\ {{I_2}} \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} {{h_{11}}}&{{h_{12}}}\\ {{h_{21}}}&{{h_{22}}} \end{array}} \right]\left[ {\begin{array}{*{20}{c}} {{I_1}}\\ {{V_2}} \end{array}} \right]\)
V1 = h11I1 + h12V2
I2 = h21I1 + h22V2
With the output short-circuited, i.e. V2 = 0, the two parameters obtained are:
\({h_{11}} = {\left. {\frac{{{V_1}}}{{{I_1}}}} \right|_{{V_2} = 0}}\)
\({h_{21}} = {\left. {\frac{{{I_2}}}{{{I_1}}}} \right|_{{V_2} = 0}}\)