1 / 4

ECE 340 Lecture 37 Narrow-base P-N diode

ECE 340 Lecture 37 Narrow-base P-N diode. Note: download the “Narrow-Base/BJT” handout online!. One last touch-up before we get to bipolar transistors Let’s recall some math: What is a typical minority carrier diffusion length in Si? How does it compare to modern device lengths?.

rumer
Télécharger la présentation

ECE 340 Lecture 37 Narrow-base P-N diode

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ECE 340 Lecture 37Narrow-base P-N diode Note: download the “Narrow-Base/BJT” handout online! • One last touch-up before we get to bipolar transistors • Let’s recall some math: • What is a typical minority carrier diffusion length in Si? • How does it compare to modern device lengths? (what if 0 < x << 1?)

  2. Let’s revisit p-n carrier distributions: • Draw “usual” distributions under forward bias (see L23-L24): • Now if the n-side is shorter than the diffusion length (ℓ < Lp):

  3. Remember, the (metal) contacts at the ends of the p-n junction can be thought of as infinite source/sink of carriers • So instead of the “long” (ℓ > Lp) exponentially decaying: • We have the “narrow” or “short” ℓ < Lp linear approximation: • What is the physical meaning of the diffusion length Lp? • Note the diode is now too narrow (short) for any hole recombination in the n-region. So, all recombination happens at the contact which sets a boundary condition for our excess minority carrier concentration:

  4. Total injected (stored) minority charge at forward bias is the area under the “triangle”: • Easy to write the hole diffusion current for “narrow” diode: • Compare with “long” diode hole diffusion current from L23: • Total diode current if: • It’s a p+/n (NA >> ND) diode • It’s a p/n (NA ~ ND) diode

More Related