PN-junction diode vs light emitting diodes

In summary, LEDs vary in their electrical properties, so it is not advisable to use them in place of a PN junction diode.
  • #1
Steven Ellet
85
3
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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  • #2
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 mheslep
  • #3
Hmm, ok but is it advisable or not?
 
  • #4
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.
 
  • #5
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'
 
  • #6
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
 
  • #7
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.
 
  • #8
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.
 
  • #9
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.
 

FAQ: PN-junction diode vs light emitting diodes

1. What is the difference between a PN-junction diode and a light emitting diode (LED)?

A PN-junction diode is a semiconductor device that allows current to flow in only one direction. It is typically used for rectification and switching applications. On the other hand, an LED is a type of diode that emits light when current passes through it. It is commonly used for lighting and display purposes.

2. How are the constructions of PN-junction diodes and LEDs different?

PN-junction diodes are made up of a p-type and an n-type semiconductor material that are fused together, creating a depletion zone between them. LEDs, on the other hand, have an additional layer of doped material called the active layer, which is responsible for emitting light when current flows through it.

3. Which one is more efficient, a PN-junction diode or an LED?

In terms of energy efficiency, LEDs are more efficient than PN-junction diodes. This is because PN-junction diodes convert a small portion of the energy they receive into light, while the rest is dissipated as heat. LEDs, on the other hand, are specifically designed to emit light, making them more energy-efficient.

4. Can a PN-junction diode be used as an LED?

No, a PN-junction diode cannot be used as an LED. As mentioned earlier, LEDs have an additional active layer that allows them to emit light. Without this layer, a diode cannot produce light.

5. What are the applications of PN-junction diodes and LEDs?

PN-junction diodes are commonly used in electronic circuits for rectification and switching purposes. They are also used in power supplies, voltage regulators, and signal amplifiers. LEDs, on the other hand, are used in a wide range of applications, including lighting, displays, indicators, and optoelectronics.

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