How come when you reverse a diode the current/voltage? is zero?

In summary, the conversation discusses the behavior of a diode in reverse bias and the analogy of a cliff for electrons. The Wikipedia page for the diode equation is recommended for further understanding. Additionally, the conversation clarifies that the discussion pertains to a common diode rectifier for vacuum tubes, not semiconductor diodes.
  • #1
mmmboh
407
0
Hi I have been looking through my book, and even online for the answer because I don't understand why this happens, but I can't find the proper answer anywhere...can someone help me? Thanks.
 
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  • #2
mmmboh said:
Hi I have been looking through my book, and even online for the answer because I don't understand why this happens, but I can't find the proper answer anywhere...can someone help me? Thanks.

Actually, it doesn't go to zero in reverse bias, it goes to a small reverse leakage current Is.

Here's a reasonable intro:

http://en.wikipedia.org/wiki/Diode

You need to look at the "diode equation" and its plot at that page to see the overall diode I(v) characteristic.
 
  • #3
Imagine a diode as being like a cliff for the electrons. It's much easier to jump off the cliff, but much more difficult to climb back up. It's not a perfect analogy, but if you think of it in terms of potential barriers that is quite close to what is happening. If you're looking for more than an analogy then the Wikipedia page is probably a good start :)
 
  • #4
For a common diode rectifier such as the 35Z5 used in transformerless AM radios, electrons flow to the plate (pin 5) from the cathode (pin 8) when the cathode is negative relative to the plate, and stop flowing when the cathode is positive relative to the plate. The cathode is indirectly heated by the filament and is very hot, and is a good source of electrons. The plate is not.
 
  • #5
Bob S said:
For a common diode rectifier such as the 35Z5 used in transformerless AM radios, electrons flow to the plate (pin 5) from the cathode (pin 8) when the cathode is negative relative to the plate, and stop flowing when the cathode is positive relative to the plate. The cathode is indirectly heated by the filament and is very hot, and is a good source of electrons. The plate is not.

LOL. "common diode rectifier" for vacuum tubes, not semiconductor diodes. Just in case anybody was getting confused by this post.
 

1. Why does reversing a diode result in zero current/voltage?

When a diode is forward biased, it allows current to flow through it in one direction. This is because the p-n junction in the diode is in a conductive state. However, when the diode is reverse biased, the p-n junction becomes non-conductive, preventing any current flow. Therefore, the current and voltage are zero in this direction.

2. How does a diode work in forward and reverse bias?

In forward bias, the diode acts as a closed switch, allowing current to flow through it. This is because the p-n junction is in a conductive state, allowing electrons to easily cross the junction. In reverse bias, the diode acts as an open switch, preventing any current flow. This is because the p-n junction becomes non-conductive, making it difficult for electrons to cross the junction.

3. Can a diode be damaged by reverse bias?

Yes, a diode can be damaged by reverse bias if the voltage applied in the reverse direction exceeds its breakdown voltage. This can cause a breakdown in the p-n junction, permanently damaging the diode. Therefore, it is important to use diodes within their specified voltage limits in both forward and reverse bias.

4. Why is a diode used in electronic circuits?

A diode is commonly used in electronic circuits because it allows current to flow in only one direction. This is useful for rectifying alternating current into direct current, which is required for many electronic devices to function. Diodes also have other applications such as voltage regulation and signal modulation.

5. Are all diodes the same?

No, diodes can vary in their characteristics and applications. Some of the most commonly used diodes include the p-n junction diode, Zener diode, Schottky diode, and light-emitting diode (LED). Each type of diode has unique properties and uses, making them suitable for different electronic applications.

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