Reverse diode

  • Thread starter gracy
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  • #1
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Main Question or Discussion Point

I am not getting why there can't be (or very negligible )current in reverse diode.According to this image
upload_2014-12-13_15-3-51.png

positive terminal of battery would suck electrons from n-type and pass them to negative terminal of battery.And Negative terminal would provide electrons to p type and from there we can see in image force on electrons is opposite to electric field so electrons can easily pass the barrier and can go to n-type and hence complete the circuit(i.e initially electrons were sucked from n-type and lastly they go towards n-type)So in this way in reverse diode also there is sufficient (in good amount)current available.
Where am i going wrong?
 

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  • #4
Drakkith
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I think you need to look at what happens in the depletion zone. Not sure. (It's very late and I'm tired.)
 
  • #5
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I think you need to look at what happens in the depletion zone. Not sure. (It's very late and I'm tired.)
I have tried my best to look at all aspects.No ,matter whenever you feel comfortable ,you can answer.Please ..but do explain me this.
 
  • #6
CWatters
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With no voltage applied there is a thin depletion region at the junction. This has very few charge carriers so it acts like an insulator preventing current flow.

...Negative terminal would provide electrons to p type
If you inject more electrons into the p-type you reduce the number of holes even more and the depletion region gets wider. You also get a build up of negative charge near the junction that eventually matches the applied voltage preventing further electrons from flowing into the p-type. In this mode the diode behaves a bit like a capacitor.

Perhaps see..
http://www.science-campus.com/engineering/electronics/semiconductor_theory/diode_2.html
 
  • #7
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One important thing you must know is we say current to flow in diode iff any charge carriers "cross the junction"between p and n.

1)ē are majority in N and holes in P.
2)-ve terminal is connected to P. So it will attract holes from P side . result: holes will move away from junction and get collected in -ve terminal
3)ē will too move away from junction to the +ve terminal there in N side.
4)these two will cause widening of depletion region as majority charge carriers move sideways .
Now ur concept of small current is true . its called reverse leakage current . minority ē in P and minority holes in N will cross junction resulting in current .
 

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