Multistage AC Analysis
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[email protected] 1 Multistage Amplifier Analysis Multistage Amplifier Analysis What are we supposed to do here ? What are we supposed to do here ? • • Grounding of all the D.C. voltage sources Grounding of all the D.C. voltage sources • • Short circuit all the capacitors present Short circuit all the capacitors present • • Reconfigure the complete circuit neatly Reconfigure the complete circuit neatly • • Replace the BJT by its mathematical model Replace the BJT by its mathematical model
Transcript of Multistage AC Analysis
Multistage Amplifier AnalysisMultistage Amplifier AnalysisWhat are we supposed to do here ? What are we supposed to do here ?
•• Grounding of all the D.C. voltage sourcesGrounding of all the D.C. voltage sources
•• Short circuit all the capacitors presentShort circuit all the capacitors present
•• Reconfigure the complete circuit neatlyReconfigure the complete circuit neatly
•• Replace the BJT by its mathematical modelReplace the BJT by its mathematical model
Inductively Coupled AmplifierInductively Coupled AmplifierCircuit Diagram Circuit Diagram
VVinin
VVoutout
RR11 RR33LL11 LL22
QQ11 QQ22
CCC1C1
RR22
CCC2C2 CCC3C3
RR44 RRE2E2RRE1E1 CCE1E1
CCE2E2
+V+VCCCC
Inductively Coupled AmplifierInductively Coupled AmplifierA.C. Analysis A.C. Analysis –– Step 1 Step 1
VVinin
VVoutout
RR11 RR33
LL11 LL22
QQ11 QQ22
RR22 RR44 RRE2E2RRE1E1
Inductively Coupled AmplifierInductively Coupled AmplifierA.C. Analysis A.C. Analysis –– Step 2 Step 2
VVinin
VVoutoutRR11//R//R22 RR33//R//R44LL11
LL22
QQ11 QQ22
Inductively Coupled AmplifierInductively Coupled AmplifierA.C. Analysis A.C. Analysis –– Step 3 Step 3
VVinin
VVoutout
RR11//R//R22 RR33//R//R44XXL1L1
QQ11 QQ22
XXL2L2
Replace the BJT by itReplace the BJT by it’’s h s h –– parameter modelparameter model
IIBB
hhfefe··IIBB
BB
EE
CC
hhieie
hh –– parameter model of the BJTparameter model of the BJTApproximate Equivalent CircuitApproximate Equivalent Circuit
EE
Approximate h Approximate h –– parameter Model for CE Configurationparameter Model for CE Configuration
Inductively Coupled AmplifierInductively Coupled AmplifierReplace BJT by its h Replace BJT by its h –– parameter model parameter model
VVininVVoutoutRR11//R//R22 RR33//R//R44XXL1L1hhfe1fe1··IIB1B1 XXL2L2hhie1ie1 hhie2ie2
hhfe2fe2··IIB2B2
h h –– parameter modelparameter modelfor BJT Qfor BJT Q11
h h –– parameter modelparameter modelfor BJT Qfor BJT Q22
Inductively Coupled AmplifierInductively Coupled AmplifierA.C. Equivalent Circuit A.C. Equivalent Circuit
VVinin VVoutoutRR11//R//R22 RR33//R//R44XXL1L1hhfe1fe1··IIB1B1 XXL2L2hhie1ie1 hhie2ie2
hhfe2fe2··IIB2B2
Stage 1Stage 1 Stage 2Stage 2
IIinin IIB1B1 IIB2B2VV22
Inductively Coupled AmplifierInductively Coupled AmplifierA.C. Equivalent Circuit A.C. Equivalent Circuit
VVinin VVoutoutRR11//R//R22 RR33//R//R44XXL1L1hhfe1fe1··IIB1B1 XXL2L2hhie1ie1 hhie2ie2
hhfe2fe2··IIB2B2
Stage 1Stage 1 Stage 2Stage 2
IIinin IIB1B1 IIB2B2VV22
stage 2 causes stage 2 causes LOADING EFFECTLOADING EFFECT on stage 1on stage 1
Transformer Coupled AmplifierTransformer Coupled AmplifierCircuit Diagram Circuit Diagram
VVinin
RR11 RR33TT11 TT22
QQ11 QQ22
CCC1C1
RR22 RR44 RRE2E2RRE1E1 CCE1E1CCE2E2
+V+VCCCC
RRLL
Transformer Coupled AmplifierTransformer Coupled AmplifierA.C. Analysis A.C. Analysis –– Step 1 Step 1
VVinin
RR11 RR33TT11 TT22
QQ11 QQ22
RR22 RR44RRE2E2RRE1E1
RRLL
Transformer Coupled AmplifierTransformer Coupled AmplifierA.C. Analysis A.C. Analysis –– Step 2 Step 2
VVinin RR11//R//R22 RR33//R//R44TT11
TT22
QQ11 QQ22
RRLL VVoutout
Transformer Coupled AmplifierTransformer Coupled AmplifierA.C. Analysis A.C. Analysis –– Step 3 Step 3
VVinin RR11//R//R22 RR33//R//R44TT11
TT22
QQ11 QQ22
RRLL VVoutout
what to do about this ?what to do about this ?
Replace the BJT by itReplace the BJT by it’’s h s h –– parameter modelparameter model
Transformer Coupled AmplifierTransformer Coupled AmplifierA.C. Equivalent Circuit A.C. Equivalent Circuit
VVinin VVoutoutRR11//R//R22 RR33//R//R44hhfe1fe1··IIB1B1 nn22··RRLLhhie1ie1 hhie2ie2
hhfe2fe2··IIB2B2
Stage 1Stage 1 Stage 2Stage 2
IIinin IIB1B1 IIB2B2VV22
nn22(R(R33//R//R44//h//hie2ie2))loading effect of stage 2 loading effect of stage 2
is taken into accountis taken into account
Direct Coupled AmplifierDirect Coupled AmplifierCircuit DiagramCircuit Diagram
VVinin
VVoutout
RR11
RRC1C1 RRC2C2
QQ11QQ22
RR22 RRE2E2RRE1E1
+V+VCCCC
Direct Coupled AmplifierDirect Coupled AmplifierA.C. Equivalent Circuit A.C. Equivalent Circuit
VVinin VVoutout
RR11//R//R22 RRC1C1
RRC2C2
ββ11··rre1e1
RRE2E2RRE1E1
ββ11··IIB1B1 ββ22··rre2e2 ββ22··IIB2B2
IIE1E1 IIE2E2
IIB1B1 IIB2B2IIinin
Direct Coupled AmplifierDirect Coupled AmplifierA.C. Equivalent CircuitA.C. Equivalent Circuit
VVinin VVoutout
RR11//R//R22 RRC1C1
RRC2C2
ββ11··rre1e1
RRE2E2RRE1E1
ββ11··IIB1B1 ββ22··rre2e2 ββ22··IIB2B2
IIE1E1 IIE2E2
IIB1B1 IIB2B2IIinin
Stage 1Stage 1 Stage 2Stage 2
VV22
