Transistors - CPE213 - [4] Bipolar Junction Transistors. Bipolar Junction Transistors (BJTs) Modes of Operation

Transcription

1 P1 lectroic evices for omuter gieerig [4] iolar Juctio Trasistors Trasistors Threetermial device otrolled source Fuctios Amlificatio Switchig Tyes iolar juctio trasistor (JT) Field effect trasistor (FT) iolar Juctio Trasistors (JTs) Modes of Oeratio 4 Trasistor mitter ase ollector Trasistor mitter(ase) Juctio ollector(ase) Juctio Narrow ase mitter Heavily oed ase ightly oed Modes mitterase Juctio ias ollectorase Juctio Forwardactive Forward everse utoff everse everse Saturatio Forward Forward everseactive everse Forward

2 5 6 Forward active Mode Forwardactive Mode Forward active Mode Forwardactive Mode Forward ias at mitterase Juctio quilibrium 7 8 Forward active Mode Forwardactive Mode Forward active Mode Forwardactive Mode Forward ias at mitterase Juctio everse ias at ollectorase Juctio lectro drift lectro drift

3 9 ergy ergy ads ads ergy ergy ads ads lectric Fields lectric Fields iff. rift c F ecombiatio c F v v quilibrium Forward Active Mode 11 1 Forward active Mode Forwardactive Mode Termial Termial urrets urrets Hole Flow lectro Flow A Forward electro ijectio A Forward bias hole ijectio lectro loss by recombiatio lectro ad hold ijectio makig u reverse saturatio ollected electros curret

4 1 14 arrier jectio Termial urrets ( e q / kt 1) W b e q / kt << Forward ias at qa qa qa Wb ( cth ( Wb ( csch Wb csch Wb )tah Wb cth ) qa qa ) qa Wb cth Wb csch Wb tah ( e q / kt 1) << everse ias at urret Gai xamle 4.1 urret Trasfer atio asetoollector urret Gai trisic ocetratio: oor ocetratio at ase: iffusiooefficiet of iffusio egthof Hole: 50m ase Width:5m ross SectioalArea:5 4 cm cm 14 cm Hole: cm / s etermie Three termial currets urret trasfer ratio asetocollector curret gai

5 17 xamle 4.1 xamle 4.1 xamle / / / cm 1) ( cm.4 1) ( e e e e e kt q kt q kt q i cm d i i N 18 xamle 4.1 xamle 4.1 xamle 4.1 A tah tah )tah ( 1.9mA 50 5 csch csch ) cth csch ( 1.9mA 50 5 cth cth ) csch cth ( b b b b b b b b W qa W qa W qa W W qa W qa W W qa 19 xamle 4.1 xamle 4.1 xamle urret Trasfer atio asetoollector urret Gai 0 ircuit Symbols ircuit Symbols ircuit Symbols Trasistor Trasistor

6 1 Trasistor ofiguratios ommo ase ofiguratio ommo ase () (Grouded ase) ommo mitter () (Grouded mitter) ommo ollector () (Grouded ollector) (mitter/oltage Follower) N N N N N N 1 1 ut Termial : mitter Outut Termial : ollector ut haracteristic () ut haracteristic () A A 1 1 Aroximatio Actual ary iut voltage T 1

7 5 6 ut haracteristic () Outut haracteristic () For Si at room temerature utoff 0 uti 0.5 Active 0.7 Saturatio 0.8 varies utoff uti Saturatio Active Small hage i A : : 1 0 Saturatio urret A Outut haracteristic () ommo ase ofiguratio varies ow urret gai High oltage Gai i / i i / i 1 N Used for imedace matchig (low iut resistace ad high outut resistace) Used for high frequecy alicatios 0

8 9 0 ommo mitter ofiguratio ut haracteristic () 1 1 ut Termial : ase Outut Termial : ollector Aroximatio Actual T 1 1 Outut haracteristic () Outut haracteristic () Saturatio urret 0

9 ommo mitter ofiguratio ommo ollector ofiguratio 4 utoutut hase differece : 180 High curret gai High voltage Gai i / i i / i Used for amlifier circuits (good voltage, curret, ower gai) N 1 1 ut Termial : ase Outut Termial : mitter 1 1 ommo ollector ofiguratio 5 JT as Amlifier 6 High urret gai ow oltage Gai v i / i i / i 1 Used as buffer (uity voltage gai), curret driver (high curret gai) N / v v / v v /( v v ) 1 N 1 1 Used i switchig circuits ad digital circuits with basic gates ias ircuit

10 7 8 JT as Amlifier JT as Amlifier 1 Aroximatio 1 1 T 1 T * for forward active mode 9 40 JT as Amlifier JT as Amlifier lockig aacitor Power Suly N 1 Aroximatio v N i i v N 1 i Small Sigal T

11 41 4 JT JT as as Amlifier Amlifier JT JT as as Amlifier Amlifier Power Suly lockig aacitor v N N N ut Small Sigal 1 lockig aacitor v oad yass aacitor htt:// JT JT as as Amlifier Amlifier quivalet quivalet ircuit ircuit Power Suly For aalyzig the oeratig oit Microhoe 1 N 1 N Seaker N v N 1 N aacitors Oe ircuit v ias ircuit ( quivalet ircuits)

12 45 46 A quivalet ircuit A quivalet ircuit v N N 1 N v For small sigal aalysis (gai, iut ad outut medaces) aacitors Short ircuit oltage Sources Groud Hybridi Model (gore Outut esistace) v be r g m v be N v N 1 Small Sigal ircuit (A quivalet ircuits) r kt q q g m r g m kt A quivalet ircuit A quivalet ircuit T Model (gore Outut esistace) v be r e g m v be v N N N 1 r e kt q q r g m 1 kt r e v N 1 r v be g m v be

13 49 50 Trasistor ofiguratios JT as Amlifier ommo ase ommo mitter ommo ollector utoutut Phase i i i i urret Gai 1 High High oltage Gai High High 1 Power Gai ow High Medium ut esistace Outut esistace ow (~ ) High (~ k) Medium (~ ) Medium (~ k) High (~ k) ow (~ ) i i 51 5 xamle 4. xamle for active mode = 0.7 urret Trasfer atio = 1k 0.99 etermie resistace such that the emitter curret is equal to 1.0 ma k Fid collector ad base currets 0.99 ma A 1k 8 curret gai =.5k k for active mode = etermie all termial currets for this bias circuit (1 ) A 1.16 ma (1 ) 1.17 ma 1 1 1

14 5 54 xamle 4.4 xamle 4.4 5k 50F k 1 50F v etermie all termial voltages ad currets for biasig for active mode = urret Gai = k 50F k 1 50F v ( 1 ) 1 ma 0 0A v N 15k 500 0F v N 15k 500 0F 1.98mA 1.0 T T T ma xamle 4.4 utoff Mode v N 5k 50F 15k k F v 0F etermie voltage gai v v N be v g v v N m v be g m q kt 7.6 v v i rift urret rift urret v N 1 r v be g m v be 0 0 0

15 57 58 Saturatio Mode Outut haracteristic iffusio urret iffusio urret Forward ias everse ias Active Saturatio utoff Forward ias everse ias Switchig Switchig utoff Mode N 1 T N 1 1 N 1 A 1 A N A A

16 61 6 Switchig JT as iode 1 Saturatio Mode ( sat) 0.(forSi) N A 1 (sat ) ( sat) ( ) / ( sat) ( ) 6 Avalache reakdow (br) 0 (br)