Lect_06 - ECE442 SolidStateDevices&Circuits...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
ECE 342–Jose Schutt Aine 1 ECE 442 Solid State Devices & Circuits 6. Bipolar Transistors Jose E. Schutt-Aine Electrical & Computer Engineering University of Illinois [email protected]
Background image of page 1

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

View Full DocumentRight Arrow Icon
ECE 342–Jose Schutt Aine 2 Bipolar Junction Transistor (BJT) – First Introduced in 1948 (Bell labs) – Consists of 2 pn junctions – Has three terminals: emitter, base, collector Bipolar Junction Transistor
Background image of page 2
ECE 342–Jose Schutt Aine 3 BJT – Modes of Operation Mode EBJ CBJ Cutoff Reverse Reverse Forw. Active Forward Reverse Rev. Active Reverse Forward Saturation Forward Forward
Background image of page 3

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

View Full DocumentRight Arrow Icon
ECE 342–Jose Schutt Aine 4 BJT in Forward Active Mode (NPN)
Background image of page 4
ECE 342–Jose Schutt Aine 5 Electrons are minority carriers in the base (p-type) / (0) BE T VV pp o nn e = () ( 0 ) nE n E n dn x n IA q D A q D dx W ⎛⎞ == ⎜⎟ ⎝⎠ i C is independent of v CB Collector current: Minority electrons will diffuse in the p-type base Longitudinal Current Flow / BE T vV CnS iII e 2 E ni S A A qD n I NW = A E : cross section area of BEJ W : Effective width of base N A : doping concentration base D n : electron diffusivity q : electron charge
Background image of page 5

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

View Full DocumentRight Arrow Icon
ECE 342–Jose Schutt Aine 6 Base Current / 2 1 BE T vV Ep i B Dp AqDne i NL = D p : hole diffusivity in emitter L p : hole diffusion length in emitter N D : doping concentration of emitter Base current: Two components – Hole injection into emitter Î i B1 – Electron recombination in base Î i B2 2 n B b Q i τ = Q n : minority carrier charge in base b : minority carrier lifetime 2 / 1 (0) 22 BE T Ei nE p A AqWn QA q n W e N = Base p n p (0) n p (ideal) effective base width From area under triangle
Background image of page 6
ECE 342–Jose Schutt Aine 7 Base current has two functions ¾ Feed recombination that occur in the base ¾ Support reverse injection Base current is small because ¾ Base is thin ¾ Has large lifetime ¾ Base is much more heavily doped than emitter Longitudinal current ¾ Depends (exponentially) on emitter junction voltage ¾ Is independent of collector junction voltage ¾ Field due to collector base voltage attracts carriers but has no effect on rate of attraction BJT Operation: Longitudinal and Base Currents
Background image of page 7

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

View Full DocumentRight Arrow Icon
ECE 342–Jose Schutt Aine 8
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/24/2012 for the course ECE 342 taught by Professor Nareshshanbhag during the Spring '11 term at University of Illinois, Urbana Champaign.

Page1 / 35

Lect_06 - ECE442 SolidStateDevices&Circuits...

This preview shows document pages 1 - 9. Sign up to view the full document.

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