CHAPTER 1 TWO PORT CIRCUITS

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Introduction What is a port? It is a pair of terminals through which a current may enter or leave a network. One port or two terminal circuit -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Two Port Circuits/Networks It is an electrical network with two separate ports for input and output. No independent sources. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Network/Circuit Equations The parameters are defined in terms of open and short circuit conditions of the two ports. Impedance Z parameters Admittance Y parameters Hybrid H parameters Transmission A, B, C, D parameters -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Z parameters z11 is the impedance seen looking into port 1when port 2 is open. z12 is a transfer impedance. It is the ratio of the voltage at port 1 to the current at port 2 when port 1 is open. z21 is a transfer impedance. It is the ratio of the voltage at port 2 to the current at port 1 when port 2 is open. z22 is the impedance seen looking into port 2 when port 1 is open. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Impedance parameters (Z in ohm) Assume no independent source in the network -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Impedance parameters -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 When z11 = z22, the two-port network is said to be symmetrical. When the transfer impedances are equal (z12 = z21), and the two-port is said to be reciprocal. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Determine the Z-parameters of the following circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Find z parameter for the below circuit: -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution When port 2 open-circuit, I2=0 so, When I2=0, thus Now, when I1=0,so When port 1 open-circuit, I1=0, so: -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Exercise Find the impedance parameters of the resistive circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Given the following circuit. Find the Z parameters. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Quiz Calculate the impedance parameters of the following resistive circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Y parameters y22 is the admittance seen looking into port 2 when port 1 is shorted. y11 is the admittance seen looking into port 1 when port 2 is shorted. 4 1 3 y21 is a transfer impedance. It is the ratio of the current at port 2 to the voltage at port 1 when port 2 is shorted. y12 is a transfer admittance. It is the ratio of the current at port 1 to the voltage at port 2 when port 1 is shorted. 2 -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Admittance parameters (y) -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Admittance parameters -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Determine the y-parameters of the following circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Exercise Determine the y-parameters of the following circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Determine the y-parameters of the following circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Hybrid parameters where the h terms are called the impedance parameters, or simply h parameters, and each parameter has different units, refer above. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 h-parameters h11 = short-circuit input impedance (Ω) h12 = open circuit reverse voltage gain h21 = short circuit forward current gain h22 open circuit output admittance (S) @ (Ʊ) The procedure for calculating the h parameters is similar to that used for the z or y parameters. We apply a voltage or current source to the appropriate port, short-circuit or open-circuit the other port, depending on the parameter of interest, and perform regular circuit analysis. For reciprocal networks, h12 = -h21 -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Determine the h-parameters of the following circuit. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Transmission parameters (ABCD) T terms are called the transmission parameters, or simply T or ABCD parameters Each parameter has different units. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 ABCD Parameters In terms of the transmission parameters, a network is reciprocal if B=Negative short-circuit transfer Impedance (Ω) A=Open-circuit voltage ratio C=Open-circuit transfer Admittance (S) D=Negative short-circuit curent ratio -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Find the transmission parameters for the single-element two-port networks. -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution (a) To find A and C, consider the network below To find B and D, consider the circuit below -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution (b) To determine A and C, consider the circuit below To get B and D refer to the circuit below -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Example Determine the transmission parameters for the two-port network -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution Determine A and C leave the output port open. So I2 = 0 Obtain B and D, short circuit the output port. So V2 = 0. KCL at node a : -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 Solution Va = 3I1 and I1 = (V1-Va)/10 Replace Va in I1 so : Va = 3I1 and V1 = 13I1 Next replace Va into give -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

Conversion of two-port parameters -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017

EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017 -suhaizal- EKT119 ELECTRIC CIRCUIT II-SEM I 2016-2017