PN Junctions vs Transistors When Building Logic Gates

Click For Summary

Discussion Overview

The discussion revolves around the reasons for using transistors instead of PN junctions in the construction of logic gates, particularly in the context of CMOS technology. Participants explore the functional differences and advantages of each component in logic gate applications.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions the cost-efficiency of using PN junctions over transistors for building logic gates.
  • Another participant points out that both PN junctions and transistors can function as switches and are voltage-controlled, prompting a comparison of their operational characteristics.
  • A participant notes that a PN junction has two contacts while a transistor has three, suggesting this may be a significant factor in their functionality.
  • A later reply emphasizes that transistors are constructed from PN junctions, indicating a relationship between the two components.

Areas of Agreement / Disagreement

Participants express differing views on the advantages of transistors over PN junctions, and the discussion remains unresolved regarding the optimal choice for logic gate construction.

Contextual Notes

Some assumptions about cost, efficiency, and the specific applications of PN junctions versus transistors are not fully explored, leaving room for further discussion.

Vishera
Messages
72
Reaction score
1
Is there any reason why logic gates are built using transistors instead of PN junctions? Wouldn't it be more cost-efficient to use PN junctions? I am referring to CMOS logic gates.

Also, what can a transistor do that a PN junction can't?
 
Physics news on Phys.org
Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
 
It seems to me that both PN junctions and transistors act as switches. And both switches are voltage-controlled. So what advantage does a transistor have over a PN junction? When the voltage is high on a PN junction, it is in forward bias and it allows current to pass though. When the voltage is low on a PN junction, it is in zero bias and it does not allow current to pass through. When a NPN bipolar transistor's base voltage is high, it allows current to pass through. When a NPN bipolar transistor's base voltage is low, it does not allow current to pass through.

EDIT: Actually, I think I get it now. A PN junction has only two contacts while a transistor has three contacts.
 
I'm glad you realized the problem: transistors are made out of PN junctions!
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 19 ·
Replies
19
Views
5K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
1
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K