In your derivation of Pn we used an equation of Vbi that was derived when there was no external field applied ,while as here we have an external potential of Vo,so how can one use the former equation here.? Thank you dear.
Hi! I didn't understand one thing, for the calculation of pn0 you used an equation that is valid in equilibrium, but we aren't in this situation, so im confused abuot that... Thanks
I am having trouble understanding why a positive voltage inherently pulls down the energy of electrons. I know that voltage is Exm. And that the energy stored in a field is proportional to field^2. I think the relative heights here imply a voltage specifically in the positive x-direction. That is what I am missing. And if the energy represented by the heightened band really represents a field in the positive X-dir, then a field that opposes that field would decrease the relative potential energy. I just never think of the field as existing outside of the depletion region, which is why it is confusing for me. But if you complete the circuit then I guess the field exists in the whole circuit.
The reason is that electrons have a negative charge, and band diagrams are drawn in terms of energy. The energy of a charged particle in a voltage field is charge * voltage, or for an electron (-q) * V.
From my understand, He didn't set those equal. The boxed equation in 12:00 is the right equation ONLY for hole concentration at the EDGE (His derivation of that equation is by using BULK hole concentration. It is a little cheating. I will explain why it works out later). To get the BULK hole concentration with external potential, you need to set external voltage to zero in the boxed equation. This is because the bulk hole concentration is at a place very far from the depletion zone, so the bulk hole concentration with external voltage=bulk hole concentration without external voltage=EDGE hole concentration without external voltage. (The last equality is because there is essentially no current through the depletion region when there is no external voltage, so no hole nor free electrons transport over depletion region. Without external voltage, edge is just as stable as bulk in terms of fraction of holes versus free electrons) (Now about the cheating, I guess the "first order information" of the external voltage is all in the "replacement rule" inside the exponential. The form of the equation out side of the exponential is kind of "zeroth order")
@@dimi5929 we want to find {edge hole concentration with external potential}. What I mean by "zeroth order" is {edge hole concentration without external potential} which approximately equals {bulk hole concentration without external potential}, assuming not a lot of holes and electrons are moving across the depletion zone. what I meant by "firstth order" is a non-rigorous. I just mean the most relevant information of external potential is inside the exponent. other less relevant external potential dependency can be, say, a prefactor (as a function of external potential) that changes much less dramatically than the exponential. I'm just guessing...the video skipped a step I think.
Your explanation doesnt work if for reverse bias ? as i understood, the band diagram is the energy of electrons, so they will have a natural tendency to go down in energy which is why there is a barrier potential... but if we are in reverse bias, the barrier potential is higher, thus an electon in the P region will be able to go down in energy by goind in the N regions, thus creating a current. Is it prevented by recombination of the election in the P region with a hole ?
How do we know if this digram is drawn to represent either the energy of electrons or the holes ? you said something like we read it from the bottom to top but I did not get this point please answer me quickly
By convention, these energy diagrams are drawn for the energy of an electron. If you look at them “from the bottom” or “upside down” you can also think about them as representing the energy of a hole.
@@JordanEdmundsEECS so when I think of them as digreams that represent the energy of electrons and when I think of them as diagrams that represent the energy of the holes?
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The best explanation I've found so far. Thanks!
"It s very important, you should get that tattooed somewhere" LOL
got alot of tattoos thx to you
Really hope you could make some JFET videos. Thank you so much!
Thank you for this great explanation !
In your derivation of Pn we used an equation of Vbi that was derived when there was no external field applied ,while as here we have an external potential of Vo,so how can one use the former equation here.? Thank you dear.
Hi!
I didn't understand one thing, for the calculation of pn0 you used an equation that is valid in equilibrium, but we aren't in this situation, so im confused abuot that... Thanks
I'm confused too.
Hi! When you say "equilibrium", do you mean the state in infinite time after all transients, even with applied voltage?
Yup
Hi Dr Edmunds, can you check if my sub-comment in
Sigangsa Baglari's comment is correct?
4:55 how to derive or rigorously reason this "dragged down" mathematically?
I am having trouble understanding why a positive voltage inherently pulls down the energy of electrons. I know that voltage is Exm. And that the energy stored in a field is proportional to field^2.
I think the relative heights here imply a voltage specifically in the positive x-direction. That is what I am missing. And if the energy represented by the heightened band really represents a field in the positive X-dir, then a field that opposes that field would decrease the relative potential energy.
I just never think of the field as existing outside of the depletion region, which is why it is confusing for me. But if you complete the circuit then I guess the field exists in the whole circuit.
The reason is that electrons have a negative charge, and band diagrams are drawn in terms of energy. The energy of a charged particle in a voltage field is charge * voltage, or for an electron (-q) * V.
Why did you take hole concentration at the edge of depletion region as equal to the hole concentration of the bulk?
From my understand,
He didn't set those equal. The boxed equation in 12:00 is the right equation ONLY for hole concentration at the EDGE (His derivation of that equation is by using BULK hole concentration. It is a little cheating. I will explain why it works out later). To get the BULK hole concentration with external potential, you need to set external voltage to zero in the boxed equation. This is because the bulk hole concentration is at a place very far from the depletion zone, so the bulk hole concentration with external voltage=bulk hole concentration without external voltage=EDGE hole concentration without external voltage. (The last equality is because there is essentially no current through the depletion region when there is no external voltage, so no hole nor free electrons transport over depletion region. Without external voltage, edge is just as stable as bulk in terms of fraction of holes versus free electrons)
(Now about the cheating, I guess the "first order information" of the external voltage is all in the "replacement rule" inside the exponential. The form of the equation out side of the exponential is kind of "zeroth order")
@@bohanxu6125 what is zeroth order?
@@dimi5929
we want to find {edge hole concentration with external potential}. What I mean by "zeroth order" is {edge hole concentration without external potential} which approximately equals {bulk hole concentration without external potential}, assuming not a lot of holes and electrons are moving across the depletion zone.
what I meant by "firstth order" is a non-rigorous. I just mean the most relevant information of external potential is inside the exponent. other less relevant external potential dependency can be, say, a prefactor (as a function of external potential) that changes much less dramatically than the exponential.
I'm just guessing...the video skipped a step I think.
Your explanation doesnt work if for reverse bias ?
as i understood, the band diagram is the energy of electrons, so they will have a natural tendency to go down in energy which is why there is a barrier potential... but if we are in reverse bias, the barrier potential is higher, thus an electon in the P region will be able to go down in energy by goind in the N regions, thus creating a current. Is it prevented by recombination of the election in the P region with a hole ?
thank u
what happens when V becomes greater than Vbi?
Current starts to flow
How do we know if this digram is drawn to represent either the energy of electrons or the holes ? you said something like we read it from the bottom to top but I did not get this point
please answer me quickly
By convention, these energy diagrams are drawn for the energy of an electron. If you look at them “from the bottom” or “upside down” you can also think about them as representing the energy of a hole.
@@JordanEdmundsEECS so when I think of them as digreams that represent the energy of electrons and when I think of them as diagrams that represent the energy of the holes?
.