MIT6_012s09_lec14

MIT6_012s09_lec14 - MIT OpenCourseWare http/ocw.mit.edu...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT OpenCourseWare http://ocw.mit.edu 6.012 Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lecture 14 The pn Junction Diode (I) I-V Characteristics Outline pn junction under bias IV characteristics Reading Assignment: Howe and Sodini; Chapter 6, Sections 6.1-6.3 6.012 Spring 2009 Lecture 14 1
Background image of page 2
1. PN junction under bias Focus on intrinsic region: meKd contact to p dde l(~dL metd contact to n side Upon application of voltage: Electrostatics upset: - depletion region widens or shrinks Current flows - With rectifying behavior Carrier charge storage 6.012 Spring 2009 Lecture 14
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
I-V Characteristics 0.25 0 0.50 0.75 V D (V) I D ( µ A) 0.25 18 19 20 100 200 300 100 200 (a) (b) V D (mV) I D ( µ A) (log scale) 500 550 600 650 700 750 10 2 0.1 1 10 100 10 3 800 slope q kT V BD Forward Bias Reverse Bias Breakdown To model I-V characteristics we need 2 concepts The Law of the Junction Steady-State Diffusion 6.012 Spring 2009 Lecture 14 3
Background image of page 4
Carrier Profiles: in thermal equilibrium In equilibrium: dynamic balance between drift and diffusion for electrons and holes inside SCR. J drift = J diff ln p o , n o p o n o N d n i 2 N d x 0 N a n i 2 N a J h diff J h drift J e diff J e drift 6.012 Spring 2009 Lecture 14 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Carrier Profiles: under forward bias Current balance in SCR broken: J drift < J diff For V>0, φ B - V ↓ ⇒ |E SCR | ↓ ⇒ |J drift | Net diffusion current in SCR minority carrier injection into QNRs. Carrier flow can be high because lots of minority carriers are injected into QNRs from the majority side. ln p, n p o p n o n N d n i 2 N d x 0 N a n i 2 N a J h diff J h J e J h drift J e diff J e drift 6.012 Spring 2009 Lecture 14 5
Background image of page 6
Carrier Profiles: under reverse bias Current balance in SCR broken: J drift > J diff For V<0, φ B - V ↑ ⇒ |E SCR | ↑ ⇒ |J drift | Net drift current in SCR
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 17

MIT6_012s09_lec14 - MIT OpenCourseWare http/ocw.mit.edu...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online