Diffusion Current Example

[@Rogue_Art]

How in the world do you teach this effectively? I could read my book for hours and I don't understand what they're trying to say that's shrouded in these big words and long derivations. But I watch just one of your videos and the material becomes as easy to read as a children's book. I'm truly impressed by how effective a good teacher like you can be. Keep up the great work and I hope to go through this entire playlist soon!

[@EagleLogic]

Thanks for the example. Helped tie together last few videos

[@satyanarayanpande4851]

In the previous video, it was derived that Dn = q * delta(x) * Vth..... and thus Jn = Dn * (dn / dx) But now, here we are using Jn = q * Dn * (dn / dx)....I'm confused!

[@JordanEdmundsEECS]

Wow, can't believe I missed that, thanks! Dn should not include q (it should only be delta(x)*Vth), and so Jn = q * Dn * (dn/dx) is correct.

[@satyanarayanpande4851]

@@JordanEdmundsEECS Thanks for the clarification!!

[@mixwaffles2127]

this solved my homework problem so easily, thank you so much

[@sahhaf1234]

I think in the plot @7:00 the diffusion current (ie, the green curve) must be negative... Electron density decreases from the left to the right, hence the electron diffusion current must be from left to right, ie positive. But the electric current is in the reverse direction to the electron current, hence it should be negative. Actually, the numeric results you've derived are also negative. A minor point, yes, but I just wanted to make sure.

[@samanthajaneamen2298]

If i'm given a hole concentration, how can i turn it into a fucntion of x?

[@dannchan00]

It's me again (biologist), Dr. Jordon, is the value n(x), Ln and Dn changes differently from other material or are fixed like a q constant? The values u mentioned in this video are based on Silicon ?

[@JordanEdmundsEECS]

Yup, Silicon. Dn and Ln will depend on the material. Dn you can calculate if you know the mobility using the Einstein relation (kT/q =D/u) - it rhymes! Ln is more difficult because you need the carrier lifetime, which you really have to measure. You can look up what “typical” values are in papers but they are all over the place any vary by orders of magnitude.

[@xuanshichen8349]

why it is not Jn + Jp

[@AkramElhilali]

I do not understand what Ln does it mean! and where the first equation of n(x) comes?