EE 434 Lecture 22. Bipolar Device Models

Transcription

1 EE 434 Lcur 22 Bipolar Dvic Modls

2 Quiz 14 Th collcor currn of a BJT was masurd o b 20mA and h bas currn masurd o b 0.1mA. Wha is h fficincy of injcion of lcrons coming from h mir o h collcor?

3 1 And h numbr is

4 1 And h numbr is

5 Quiz 14 Th collcor currn of a BJT was masurd o b 20mA and h bas currn masurd o b 0.1mA. Wha is h fficincy of injcion of lcrons coming from h mir o h collcor? Soluion: Efficincy α β B α β 1 α 20mA.1mA 200 α β 1+ β α

6 Rviw from Las Tim Bipolar dvic opraion dpndn upon how minoriy carrirs in bas conribu o collcor currn Bipolar modl (in high gain rgion) Diod modl for juncion, injcion fficincy for α B ~ S β ~ S 1 B β Bipolar ransisor is inhrnly a currn amplifir wih xponnial rlaionship bwn collcor currn and This propry maks BJT vry usful β ~ S

7 Bipolar Modls Simpl dc Modl Small Signal Modl Br Analyical dc Modls Sophisicad Modl for ompur Simulaions Frquncy-Dpndn Small Signal Modl Br Modls for Prdicing Dvic Opraion

8 Bipolar Modls Simpl dc Modl Small Signal Modl Br Analyical dc Modls Sophisicad Modl for ompur Simulaions Frquncy-Dpndn Small Signal Modl Br Modls for Prdicing Dvic Opraion

9 Bipolar Modls Simpl dc Modl following convnion, pick and B as dpndn variabls and and E as indpndn variabls

10 Simpl dc modl From las im : B ~ S β ~ S kt q This has h propris w ar looking for bu h variabls w usd in inroducing hs rlaionships ar no sandard ~ can b shown ha S is proporional o h mir ara A E ~ β 1 S J S A E Dfin and subsiu his ino h abov quaions

11 Simpl dc modl B ~ S β ~ S kt q B J J kt q S S A β A E E J S is rmd h sauraion currn dnsiy Procss Paramrs : J S,β Dsign Paramrs: A E Environmnal paramrs and physical consans: k,t,q A room mpraur, is around 26m J S vry small around.25fa/u 2

12 Transfr haracrisics J S.25fA/u 2 A E 400u (ma) clos o 0.6 for a wo dcad chang in around 1mA

13 Transfr haracrisics J S.25fA/u 2 A E 400u (ma) clos o 0.6 for a four dcad chang in around 1mA

14 Simpl dc modl Oupu haracrisics d or B E ds J S A E

15 Simpl dc modl Br Modl of Oupu haracrisics d or B E ds

16 Simpl dc modl Typical Oupu haracrisics Sauraion Forward Aciv d 150 or B ds uoff E Forward Aciv rgion of BJT is analogous o Sauraion rgion of MOSFET Sauraion rgion of BJT is analogous o Triod rgion of MOSFET

17 Simpl dc modl Typical Oupu haracrisics d 150 or B ds E Projcions of hs angnial lins all inrcp h E axis a h sam plac and his is rmd h Early volag, AF (acually AF is inrcp) Typical valus of AF ar in h 100 rang

18 Simpl dc modl mprovd Modl d 150 or B E ds E JS AF B JSA β E 1 + alid only in Forward Aciv Rgion

19 Simpl dc modl mprovd Modl d 150 or B E kt q 100 B J A S E + 1 J A 1 S E α F B J SAE J 1 1 SAE α R ds E alid in All rgions of opraion AF ffcs can b addd No mahmaically asy o work wih No dpndn variabls changs Trmd Ebrs-Moll modl Rducs o prvious modl in FA rgion

20 Simpl dc modl Ebrs-Moll modl kt q E B J A S E + 1 J A 1 S E α F B J SAE J 1 1 SAE α R Procss Paramrs: {J S, α F, α R } Dsign Paramrs: {A E } α F is h paramr α discussd arlir α R is rmd h rvrs α α F β F 1-α F α R β R 1-α R Typical valus for procss paramrs: J S ~10-16 A/µ 2 β F ~100, β R ~0.4

21 Simpl dc modl Ebrs-Moll modl E omplly dominan! B J A S E + 1 J A 1 S E α F B kt J SAE 1 1 JS AE q α R Wih ypical valus for procss paramrs in forward aciv rgion ( ~0.6, B ~-3), wih 26m and if A E 100µ 2 : J S ~10-16 A/µ 2 β F ~100, β R ~0.4 B J SAE J 1 1 SAE α R x10 7.7x ( ) ( ) Maks no sns o kp anyhing ohr han S E J A in forward aciv

22 Simpl dc modl Ebrs-Moll modl kt q E B J A S E + 1 J A 1 S E α F B J SAE J 1 1 SAE α R Alrna quivaln xprssions for dpndn variabls {, B } dfind arlir for Ebrs-Moll quaions in rms of indpndn variabls {, E } - 1+β R J A 1 S E β R -E 1 1 J A - B S E β β F R No mor usful han prvious quaion bu in form consisn wih noaion nroducd arlir E

23 Simpl dc modl Simplifid Muli-Rgion Modl Ebrs-Moll Modl Simplifid Muli-Rgion Modl -E 1+β R E J A 1 1+ S E β R AF 1 1 β β F R E J A - B S E - + E JSAE 1 AF JSAE B β 0.7 E 0.2 Forward Aciv Sauraion B 0 uoff

24 Simpl dc modl Simplifid Muli-Rgion Modl E JSAE AF JSA B β kt q E 1 + Forward Aciv 0.7 E 0.2 Sauraion B 0 uoff

25 Simpl dc modl Simplifid Muli-Rgion Modl E JSAE AF JSA B β E 1 + >0.4 B <0 Forward Aciv kt q 0.7 E 0.2 <β B Sauraion B 0 <0 B <0 uoff A small porion of h opraing rgion is missd wih his modl bu sldom opra in h missing rgion

26 Simpl dc modl Equivaln Simplifid Muli-Rgion Modl β 1 + E B AF JSA B β E >0.4 B <0 Forward Aciv kt q 0.7 E 0.2 <β B Sauraion B 0 <0 B <0 uoff A small porion of h opraing rgion is missd wih his modl bu sldom opra in h missing rgion