What is so special about TWO PORT NETWORKS

[shippo113]

Why is there so much talk about two port networks in books and stuff I don't fully understand, what happens if a thing is not two port?

 

[yungman]

Because a lot of the electronic components can be represented by 2 port network and with that, you can cascade them together and get the final transfer function. Resistors, capacitors, inductor and transistors can all represent as 2 port networks of various kind.

Also a lot of data sheets of transistors are given as S-parameters or H parameters(remember hoe is like beta of transistor?). Those are two port networks.

 

[shippo113]

hmm, what other type of networks do we have anyway? 3 port networks?
Wait Resistors and Capacitors e.t.c have only 2 ports, so how can we cascade them? One input port and one output port.
For 2 port systems we need to have 2 inputs and 2 outputs right, where one input and one output is grounded and the actual signal is present on the remaining input/output terminal right?

 

[yungman]

hmm, what other type of networks do we have anyway? 3 port networks?
Wait Resistors and Capacitors e.t.c have only 2 ports, so how can we cascade them? One input port and one output port.
For 2 port systems we need to have 2 inputs and 2 outputs right, where one input and one output is grounded and the actual signal is present on the remaining input/output terminal right?

You have to look at the definition of the particular 2 port parameters. Read this first and then come back:

http://en.wikipedia.org/wiki/Two-port_parameters

Pick one easy one like Z parameter and fit a resistor in series or shunt and work out the Z11, Z12, Z21 and Z22.