In electronics, why do we need a two port network?

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Discussion Overview

The discussion revolves around the necessity and functionality of two-port networks in electronics, contrasting them with one-port networks. Participants explore the implications of having multiple ports in circuit design and the types of components that require such configurations.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants suggest that a one-port network lacks a second port, which is essential for more complex arrangements of components.
  • Others argue that almost all electronic devices would not function with only one port, questioning how components like amplifiers or power supplies could be implemented in such a scenario.
  • A participant raises a question about the relevance of two-port circuits that consist solely of linear resistances, seeking clarification on their significance.
  • There is a discussion about the definition of a port, with some asserting that a port consists of two terminals, while others clarify that a two-port device has four terminals or three with one common terminal.
  • Some participants note that a one-port network can model simple two-terminal circuit elements, while a two-port network can represent more complex systems, including transfer functions and dependent sources.
  • It is mentioned that transfer functions are common in circuit modeling, making the two-port concept useful for generic linear circuit models.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of ports in circuit design. While some agree on the necessity of two-port networks for certain functions, others challenge the definitions and classifications of ports and their roles in active devices.

Contextual Notes

There are unresolved definitions regarding what constitutes a port in active devices and the implications of power supply connections in this context. The discussion includes varying interpretations of circuit elements and their classifications.

meisnkp
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Why do we need a two port network? Is there something which a one port network lacks? Why we needed a two port network connection?
 
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Welcome to PF;
What a 1-port network lacks is a second port.
The second port on the input and the output allows for more complicated arrangements of components.
Almost all electronics devices would not function with only one port.
For instance - how do make an amplifier with only one port? How do you add a power supply with only one port?
(Note: the ground can be the second port.)
 
Hmm...thanks
 
But what about the two port circuits with only simple linear resistances (and not any non-linear elements like transistor s)? What's special in that?
 
Simon Bridge said:
Welcome to PF;
What a 1-port network lacks is a second port.
The second port on the input and the output allows for more complicated arrangements of components.
Almost all electronics devices would not function with only one port.
For instance - how do make an amplifier with only one port? How do you add a power supply with only one port?
(Note: the ground can be the second port.)

I am not sure about that. Ifaikr, a 'port' consists of two terminals - e.g between an input terminal and ground or two input connections. A two port device would have four terminals or possibly three terminals with one 'common', which may or may not be 'ground'. I don't think the power supply connections are classed as ports in an active device.

A single port network would just have two terminals - such as a resistor (the simplest), an RC or RLC network or a more complicated circuit that might even be active.

We "need" two port networks if we want to have all those functions that amplifiers, transformers and matching networks provide.
 
sophiecentaur said:
I don't think the power supply connections are classed as ports in an active device.

yes agreed ... a port is an I/O type port input only, output only, or bi directional
and may be considered analog or digital


Dave
 
A one port models a single 2-terminal circuit element.

A two port models a transfer function or similar system component as wells ladder and tee circuit elements. Dependent sources, for example, are 2-ports. A transfer function of the form y = A x is a 2-port.

Since transfer functions are extremely common it's nice to have a very generic linear circuit model concept for them.
 

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