Chng 5:TRANSISTOR LNG CC (BJT)ThS. Nguyn B Vng1. Cu to Transistor c cu to gm cc min bn dn p v n xen k nhau P n PE CB0.150 in0.001 inn p nE CB0.150 in0.001 in1. Cu to Min bn dn th nht ca Transistor lmin Emitter (min pht) vi c im l cnng tp cht ln nht, in cc ni vimin ny gi l cc Emitter (cc pht). Min th hai l min Base (min gc) vinng tp cht nh v dy ca n nhc m, in cc ni vi min ny gi l ccBase (cc gc). Min cn li l min Collector (min thu) vinng tp cht trung bnh vin cctng ng l Collector (cc thu).1. Cu to Tip gip p-n gia min Emitter v Base gi ltip gip Emitter (JE). Tip gip p-n gia min Base v min Collectorl tip gip Collector (JC). V k hiu Transistor cn ch l mi tn t gia cc Emitter v Base c chiu t bn dn psang bn dn n.PNP NPN1. Cu to V mt cu trc, c th coi Transistor nh 2diode mc i nhau1. Cu to Cu to mch thc t ca mt Transistor n-p-n2.Nguyn l hot ng Transistor lm vic, ngi ta phi a in p 1 chiu ticc in cc ca n, gi l phn cc cho Transistor2.Nguyn l hot ngs phn cc trong BJTJEJCs phn cc trong BJTJEJCTham s H thc c bn v cc dngin trongTransistor H s truyn t dng in caTransistor H s khuch i dng in caTransistor Ta c h thc:E B CI I I = +CEII= CBII= (1 )E BI I = + (1 )=+ 3. Cc dng mc BJT3.1 Mch chung Emitter (EC)CBEInOutECH ung c tuyn voIB= f(UBE) khi UCE= constIB(A)VBE (V)0501001500.5 1VCE=2VVCE=4VVCE=6VCBEUInUOutECVAVAc tuyn truyn at v c tuyn ra ca so ECH ung c tuyn ra: IC= f(UCE) khi IB=const H ung c tuyn truyn at: IC= f(IBE) khi UCE= constUCE=8VUCE=3VH s khuch aiTheo nh lut Kichp ta c E B CI I I = +( )0 0= + = + +C E CB C B CBI I I I I I Gii phng trnh vi IC, chng ta c mi quan h gia IC v IB ( )0 0 0111 1= + = + + = + C B CB B CB B CBI I I I I I I Trong = (1-) l h s khuch i CE ( thng thng = 0,99; = 99) Mt s mach ECR110kR247kR34k7R51kQ12N2222C122uF+10VC3100uC222uFR410k3.2 Mch chung Base (BC) H ung c tuyn voIE=f(UEB) khi in p ra UCB=constH ung c tuyn ra v truyn atc tuyn ra:IC= f(UCB) khi gi dng vo IE=constc tuyn truyn at: IC=f(IE) khi khi UCB= constCBCB3.3 Mch chung Collector (CC) H ung c tuyn voc tuyn ra ca s CCng thng ly in (Load line) Phng trnh ng thng ly in : VCC=ICRC+VCEvit li: IC= ( VCC VCE)/ RC= -VCE/ RC+ VCC/RC ng ly in c v trn c tuyn ra qua 2 im xc nh sau: im ngng, IC= 0VCE= VCC(im M) im bo ha: VCE= 0IC= VCC/ RC(im N)ni 2 im M v N li ta c c ng ly in Giao im ng ly in v ng phn cc IBchn trc cho ta tr s im tnh Q.0IC(mA)VCE(V)IB(A)QNMngngbo haVCEQICQng thng ly in cho ECVai tr ca ng thng ly in Phn gii mch Transistor. Xc nh im tnh iu hnh Q. Cho bit trng thi hot ng ca transistor ( tc ng, bo ho, ngng). Mch khuch i c tuyn tnh hay khng. Thit k mch khuch theo nh ( chn trc im tnh Q , tnh cc tr s linh kin)Ch : li dng in thay i theo v tr im tnh iu hnh Q. im tnh iu hnh Q thay i v tr theo in th phn cc transistor v cnthay i theo tn hiu xoay chiu ( AC) tc ng vo mch .Phn gii bng thIB(A)VBE (V)0200.5 1VCE=4V024682 4 6 8 10IC(mA)UCE(V)10IB=20AIB=80AIB=60AIB=40AIB=100A406080100VBEQttIBQQtICQIC+IC-UCEQUC+UC-t4. Phn cc ca BJTVng hot ng ca BJT:Vng tc ng: (Vng khuch i hay tuyn tnh) Mi ghp B-E phn cc thun Mi ghp B-C phn cc nghch Vng bo ha:Mi ghp B-E phn cc thun Mi ghp B-C phn cc thun Vng ngng: Mi ghp B-E phn cc nghch Phng php chung phn gii mch phn cc gm ba bc: Bc 1: Dng mch in ng vo xc nhdng in ng vo (IBhoc IE). Bc 2: Suy ra dng in ng ra t cc lin hIC=IBhay IC=IE Bc 3: Dng mchin ng ra tm ccthng s cn li (in th ti cc chn, gia ccchn ca BJT...)4.1 Phn cc c nh ca BJT (Fixed Bias)VCE+-VBE+RCRBVccICIBPhn cc c nh ca BJT (Fixed Bias) Mch ng nn-pht (Base-Emitter): Vi VBE= 0.7V nu BJT l Si v VBE= 0.3V nu l Ge.Suy ra : IC=IBMch ng ra thu-nn (Collector-Base): hay 0 =CC B B BEV RI VCC BEBBV VIR == +CC C C CEV RI V = CE CC C CV V RIy l phng trnh ng thng ly in. S bo ha ca BJT S lin h gia ICv IBs quyt nh BJT c hot ngtrong vng tuyn tnh hay khng. BJT hot ng trongvng tuyn tnh th ni thu - nn (CE) phi phn cc nghch. BJT NPN v c th mch va xt ta phi c:C B C B BEV V V V V > > = 0.7C CC C C CE BEV V RI V V V = = > =0.7CCCCVIR VBIB IC VC(t)=VCC-RCiC(t) VB(t)