Introduction to Two-Port Networks


Hey friends, welcome to the YouTube channel
ALL ABOUT ELECTRONICS. So, in this video, we will learn about the
Two-Port Network. So, as its name suggests, the two-port network
is the electrical circuit or the network which contains the two ports. But to understand it in detail, first of all,
we need to understand what is port? So, the port is the pair of two terminals
which connect the electrical circuit or the network to the external circuit. So, through this port, any external network
or any independent source can be connected to the existing network. But any two terminals can not be called as
a port. And for that, they need to satisfy the port
condition. That means if the current I enter through
the one terminal of the port, then the same current should leave through the second terminal
of the port. So, If the pair of terminals satisfy this
condition then they can be called as a port. So, if the circuit or the electrical network
contains one such port then it is called the one-port network. And all the basic circuit elements, like,
the resistor, the capacitor, and the inductor are the examples of the one-port network. Similarly, if the electrical circuit or the
network contains two such ports then it is called the two-port network. And this simple T- network is an example of
the two-port network. So, here these two terminals will act as one
port, while these other two terminals will act as a second port. Similarly, if the network contains more than
two ports then it is called the multi-port network. And the directional couplers and the circulators
are the examples of the multiport network. But in this video, as well as in the upcoming
videos, we will focus on the two-port network. So, in the two-port network, this port 1 is
often considered as the input port, while the second port is considered as the output
port. And many times when the circuit or the network
is represented using the port, then it reduces the complexity during the circuit analysis. So, this two-port network model is used in
mathematical circuit analysis techniques for complex circuits. So, using this two-port network model, we
can isolate the portion of the larger circuits. So, here basically this two-port network is
regarded as the black box. And the property of this network is specified
by some parameters. So, when some input signal is applied to this
port, then the response of this network can be easily found using these network parameters. And in this case, we do not need to find the
internal voltage and current of this network. That means using this two-port network model,
we can analyze the complex circuits easily. Apart from that, using this two-port network
model, a similar type of device or the circuits can be compared easily. For example, the transistor is often regarded
as the two-port device for the small-signal analysis. And during the analysis, it is characterized
by the network parameters. So, in general, any circuit with two pairs
of terminals can be regarded as a two-port network, provided it does not contain independent
sources and it also satisfies the port condition. So, the filters, transformers, the transmission lines and the small-signal model of a transistor are the few examples where they
are treated as a two-port network during the circuit analysis. So, in this two-port network, let’s say
the voltage across the port-1 is equal to V1, while the current which is flowing through
port 1 is I1. Similarly, let’s say the voltage across
the port-2 is equal to V2 and the current which is flowing through this port 2 is equal
to I2. So, here basically there are four variables. That is V1, I1, V2, and I2. And for the analysis, out of the four variables, the two variables are
considered as the independent variables while the remaining two variables are the dependent
variables. for example, let’s say, here I1, and I2 are
the independent variables, while the V1 and V2 are the dependent variables. That means this V1 and V2 can be expressed
in terms of the independent variables I1 and I2. And based on which variables are the independent
variables, the six different models or the six different parameters can be defined for
this two-port network. So, here is the list of the different two-port
parameters. So, in the upcoming videos, we will learn
about all these different types of parameters. And we will also solve some problems based
on these two-port parameters. So, I hope in this video, you understood what
is two-port network and what is the significance of this two-port network. So, if you have any questions or suggestions,
do let me know here in the comment section below. If you like this video, hit the like button
and subscribe to the channel for more such videos.

Author: Kevin Mason

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