PN-junction diode vs light emitting diodes

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Discussion Overview

The discussion revolves around the advisability of using light-emitting diodes (LEDs) as replacements for standard PN-junction diodes in electronic circuits. Participants explore the differences in characteristics, such as resistance, threshold voltage, and thermal tolerance, while considering specific applications.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question whether it is advisable to use an LED instead of a PN-junction diode, noting that LEDs are easier and cheaper to obtain.
  • Others argue that different diodes have varying resistances, threshold voltages, current tolerances, and other characteristics, making it impossible to provide a general answer.
  • One participant clarifies that while an LED is a type of PN-junction diode, it is specifically designed to emit light, which may not be suitable for all applications.
  • Another participant emphasizes that not all diodes can be replaced with LEDs, citing various types of diodes that serve different functions and cannot be substituted without consideration of their specific properties.
  • Some participants express frustration over the vagueness of previous answers, indicating a desire for more definitive guidance on the advisability of using LEDs in place of standard diodes.
  • One participant asserts that LEDs make poor general-purpose diodes and suggests comparing specifications like reverse leakage and forward drop to understand their limitations.
  • There is a discussion about whether ordinary diodes emit light in the form of heat (IR light), with a participant noting that this is a different mechanism than that of LEDs.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the advisability of using LEDs instead of PN-junction diodes. Multiple competing views remain regarding the suitability and characteristics of different types of diodes.

Contextual Notes

Participants highlight the complexity of diode characteristics, including variations in resistance, thermal tolerance, and application-specific requirements, which complicate the decision to substitute LEDs for standard diodes.

Steven Ellet
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Is it advisable to use an LED instead of a PN-junction diode and what is the resistance of each (or do they vary)? The only reason I'm asking is LEDs are easier and cheaper to get.
P.S. What I need it for, only needs a PN-junction diode.
 
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Different parts will have different resistances, different threshold voltages, different current and heat they can tolerate, different sizes, different reverse breakdown voltages, ...
This is impossible to answer in a general way.
 
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Likes   Reactions: mheslep
Hmm, ok but is it advisable or not?
 
So an LED is a PN junction diode, its just light emitting...

So you are saying you need to use a diode in circuitry, but you replace the regular diode with an LED...
as long as they are electrically equivalent and meet thermal and package requirements there is nothing wrong with that.
 
mfb said:
Different parts will have different resistances, different threshold voltages, different current and heat they can tolerate, different sizes, different reverse breakdown voltages, ...
This is impossible to answer in a general way.
It just amazes me that after such a good answer that you still get ...
Steven Ellet said:
Hmm, ok but is it advisable or not?

Just sayin'
 
dlgoff said:
It just amazes me that after such a good answer that you still get ...Just sayin'

The answer was a little vague and did not completely answer my question
 
The question was a little vague and was not possible to answer completely.
-
Think of it this way: All LEDs are diodes, not all diodes are LEDs. To say that you could replace an LED with a diode seems silly of course since the idea of an LED is to be able to emit some type of visible or infrared radiation. There can be instances where a diode can be replaced by a simple LED such as a rectifier with low current draw load. However, there are many many many types of diodes besides LEDs. Small signal and switching diodes, power rectifiers that can handle hundreds of amperes, diodes that can switch up to a rate in the microwave region, PIN diodes used to switch RF currents, varactor diodes that are used as variable capacitors, etc. etc. Most if not all of those examples could not be substituted with an LED. There is no one size fits all here.
 
Steven Ellet said:
The answer was a little vague and did not completely answer my question
I apologies for coming off so strong in my comment. It's just that I would have liked to have seen your next question showed that you had researched the differences mfb allotted to; in relation to your diode needs.
 
Steven Ellet said:
Hmm, ok but is it advisable or not?
Not usually✻advisable.
 
  • #10
Steven Ellet said:
Hmm, ok but is it advisable or not?
No.
No way.
No how.
LED makes a poor general purpose diode.
Compare the specs for reverse leakge, reverse breakdown, forward drop, dynamic resistance, switching times, etc etc etc.
 
  • #11
But isn't the ordinary diode also emit a light in form of Heat (IR light) ;)
 
  • #12
Jony130 said:
But isn't the ordinary diode also emit a light in form of Heat (IR light) ;)
That is a completely different mechanism.
 

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