How do semiconductors affect a circuit?

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Discussion Overview

The discussion revolves around the impact of semiconductors, specifically p-n junctions, on electrical circuits. Participants explore the operational principles of p-n junctions and their effects on circuit behavior, particularly in relation to components like diodes. The scope includes theoretical understanding and practical applications within circuits.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on how adding a p-n junction to a simple circuit with a battery and light bulb would affect the circuit's operation.
  • Another participant suggests that the bulb's state (on or off) would depend on the orientation of the p-n junction relative to the battery's polarity.
  • A participant explains that a diode, which consists of a p-n junction, allows current to flow in one direction when forward biased, while blocking it in the reverse bias, effectively acting as a large resistance in that state.
  • One participant proposes breaking down the inquiry into two questions: how a p-n junction works and how it affects a circuit, indicating that understanding one does not necessarily require understanding the other.
  • The same participant describes the biasing of a p-n junction and the resulting electric field that facilitates current flow in forward mode, while preventing it in reverse mode, likening the function of a diode to a one-way valve.
  • There is a note that a comprehensive understanding of semiconductors typically requires formal education, suggesting that practical application may be more accessible than theoretical understanding.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the operation of p-n junctions and their implications in circuits. There is no consensus on a singular explanation, and multiple viewpoints on the complexity of understanding semiconductors are presented.

Contextual Notes

Participants acknowledge that a full understanding of semiconductors and their applications may require extensive study, indicating limitations in the depth of discussion possible within the forum format.

Devguy101
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I understand the difference between p-type and n-type semiconductors but I just don't understand how adding a
p-n junction to a circuit affects it.
Can someone please explain how semiconductors work?
For example, if I had a circuit with just a battery and a light bulb, what would change if I added a p-n junction right before the bulb?
 
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Devguy101 said:
what would change if I added a p-n junction right before the bulb?
The bulb would be on or off depending upon the direction of the p-n junction relative to the polarity of the battery.
 
An electronic part consisting of a simple pn junction is the DIODE. This part allows a current in one direction only - of course, caused by a corresponding voltage of (0.6...0.7) volts (forward operation). If you change the polarity of the voltage there will be no current (backward operation, off condition). Under this condition, the diode behaves like a very large resistance (nearly infinite).
 
Really I think you need to ask this as 2 questions...1) How does a PN junction work? 2) How does this affect a circuit - how is it used? I say this because you do not need to completely understand one to understand the other.

When a voltage is applied on a PN junction you are said to "bias" the junction - and sets up an electric field in the semiconductor. In the forward mode the "holes" in the P side and Electrons in the N side are pushed together by the electric field in the diode - when an electron - combines with a hole this in essence allows current flow. It is a lot more complicated but that is as simple as I can state it. In the reverse bias, the Holes and Electrons are pulled away from each other, they can not combine - and they can not conduct current.

As for use - think of the device as a one-way valve.

BTW introduction to semiconductors is a full semester EE, or Solid State Physics class - the HOW they work... granted it covers much more than diodes. I am not saying you need a semester class, but you probably can not figure it all out in a forum without a lot of research on your part. But note the Use side, how Diodes and other basic semiconductors are applied, is typically only a part of a circuit analysis course. - Using them is easier than understanding them.
 
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