Micelectnics Cicuit Analysis and Design Dnald A. Neamen Chapte 6 Basic BJT Amplifies In this chapte, we will: Undestand the pinciple f a linea amplifie. Discuss and cmpae the thee basic tansist amplifie cnfiguatins. the cmmn-emitte amplifie. the emitte-fllwe amplifie. the cmmn-base amplifie. Analyze multi-tansist amplifies. Neamen Micelectnics, 4e Chapte 6-1 Neamen Micelectnics, 4e Chapte 6-2 Cmmn Emitte with Time-Vaying Input ac Equivalent Cicuit f Cmmn Emitte Neamen Micelectnics, 4e Chapte 6-3 Neamen Micelectnics, 4e Chapte 6-4 1
I B Vesus V BE Chaacteistic ac Equivalent Cicuit exp 1 + x +.. v be i B I BQ (1 + ) = I B + ib VT Neamen Micelectnics, 4e Chapte 6-5 Neamen Micelectnics, 4e Chapte 6-6 ac Equivalent Cicuit ac Equivalent Cicuit Neamen Micelectnics, 4e Chapte 6-7 Neamen Micelectnics, 4e Chapte 6-8 2
ac Equivalent Cicuit Small-Signal Equivalent Cicuit Using Cmmn-Emitte Cuent Gain Neamen Micelectnics, 4e Chapte 6-9 Neamen Micelectnics, 4e Chapte 6-10 ac Equivalent Cicuit Small-Signal Hybid Mdel f npn BJT g g m βv = I m I = V CQ T T CQ = β Phas signals ae shwn in paentheses. Neamen Micelectnics, 4e Chapte 6-11 Neamen Micelectnics, 4e Chapte 6-12 3
Small-Signal Equivalent Cicuit f npn Cmmn Emitte cicuit A = ( g C )( Neamen Micelectnics, 4e Chapte 6-13 v m + B ) Pblem-Slving Technique: BJT AC Analysis 1. Analyze cicuit with nly dc suces t find Q pint. 2. eplace each element in cicuit with smallsignal mdel, including the hybid mdel f the tansist. 3. Analyze the small-signal equivalent cicuit afte setting dc suce cmpnents t ze. Neamen Micelectnics, 4e Chapte 6-14 Tansfmatin f Elements Element DC Mdel AC Mdel Hybid Mdel f npn with Ealy Effect esist Capacit Open C Induct Sht L Dide +V γ, f d = V T /I D Independent Cnstant Vltage Suce Independent Cnstant Cuent Suce I S + V S - Sht Open V = I A CQ Neamen Micelectnics, 4e Chapte 6-15 Neamen Micelectnics, 4e Chapte 6-16 4
Hybid p Mdel f pnp with Ealy Effect h-paamete Mdel f npn All vltage and cuent plaities ae evesed. Gain equatin ae the SAME. v = gm( C ) v = gmv ( C ) v = vs ( ) + B v = Bib ( C ) vs ib = ( ) + B V I be c = h I + h V ie = h I + h V fe b b e e ce ce KVL at input lp KCL at utput lp Neamen Micelectnics, 4e Chapte 6-17 Neamen Micelectnics, 4e Chapte 6-18 h-paamete Mdel f npn Cmmn Emitte with Vltage-Divide Bias and a Cupling Capacit h h ie fe = b = β + µ h h e e µ 1+ β 1 = + µ Neamen Micelectnics, 4e Chapte 6-19 Neamen Micelectnics, 4e Chapte 6-20 5
Small-Signal Equivalent Cicuit Cupling Capacit assumed a Sht npn Cmmn Emitte with Emitte esist i = 1 2 = c i Av = gm ( ) + i S Neamen Micelectnics, 4e Chapte 6-21 Neamen Micelectnics, 4e Chapte 6-22 Cmmn Emitte with E E and Emitte Bypass Capacit ib i = Vin / I = 1 2 b ib βc Av = + (1 + β ) = + (1 + β ) E i ( + i S E ) Neamen Micelectnics, 4e Chapte 6-23 Neamen Micelectnics, 4e Chapte 6-24 6
DC and AC Lad Lines: E and Emitte Bypass Capacit Pblem-Slving Technique: Maximum Symmetical Swing 1. Wite dc lad line equatin that elates I CQ and V CEQ. 2. Wite ac lad line equatins that elates ic and vce 3. In geneal, i c = I CQ I C (min), whee I C (min) is ze the minimum cllect cuent. 4. In geneal, v ce = V CEQ V CE (min), whee V CE (min) is sme specified minimum cllect-emitte vltage. 5. Cmbine abve 4 equatins t find ptimum I CQ and V CEQ. Neamen Micelectnics, 4e Chapte 6-25 Neamen Micelectnics, 4e Chapte 6-26 Cmmn-Cllect Emitte-Fllwe Amplifie Emitte Fllwe Neamen Micelectnics, 4e Chapte 6-27 Neamen Micelectnics, 4e Chapte 6-28 7
Emitte Fllwe S-S Equivalent :Emitte Fllwe Typically a lage value due t the eflected impedance (1 + β )( E ) i Av = ( ) 1 + (1 + β )( ) + E i S Neamen Micelectnics, 4e Chapte 6-29 Neamen Micelectnics, 4e Chapte 6-30 Output esistance: Emitte Fllwe Emitte Fllwe Cuent Gain V = I x x = E Typically a lw value due t 1 + β the eflected impedance Neamen Micelectnics, 4e Chapte 6-31 Neamen Micelectnics, 4e Chapte 6-32 8
Emitte Fllwe Cuent Gain Cmmn-Base Amplifie Neamen Micelectnics, 4e Chapte 6-33 Neamen Micelectnics, 4e Chapte 6-34 Cmmn Base Cmmn Base A g ( v m C C ) C Ai = gm ( + L L )[ 1+ β E ] Neamen Micelectnics, 4e Chapte 6-35 Neamen Micelectnics, 4e Chapte 6-36 9
Cmmn Base Cmmn Base Neamen Micelectnics, 4e Chapte 6-37 Neamen Micelectnics, 4e Chapte 6-38 Cmmn Base Cmmn Base Neamen Micelectnics, 4e Chapte 6-39 Neamen Micelectnics, 4e Chapte 6-40 10
Cmmn Emitte Cascade Amplifie Neamen Micelectnics, 4e Chapte 6-41 Neamen Micelectnics, 4e Chapte 6-42 Cascade Amplifie Dalingtn Pai A i β 1 β 2 Neamen Micelectnics, 4e Chapte 6-43 Neamen Micelectnics, 4e Chapte 6-44 11
Cascde Amplifie Cascde Amplifie A g v ( m1 C L ) Neamen Micelectnics, 4e Chapte 6-45 Neamen Micelectnics, 4e Chapte 6-46 12