Neamen Microelectronics Chapter 6-1 Microelectronics Circuit Analysis and Design Donald A. Neamen Chapter 6 Basic BJT Amplifiers
Neamen Microelectronics Chapter 6-2 In this chapter, we will: Understand the concept of an analog signal and the principle of a linear amplifier. Investigate how a transistor circuit can amplify a small, time-varying input signal. Discuss and compare the three basic transistor amplifier configurations. Analyze the common-emitter amplifier. Understand the ac load line & determine the maximum symmetrical swing of the output. Analyze the emitter-follower amplifier. Analyze the common-base amplifier. Analyze multitransistor or multistage amplifiers. Understand the concept of signal power gain in an amplifier circuit.
Common Emitter with Time-Varying Input Neamen Microelectronics Chapter 6-3
Neamen Microelectronics Chapter 6-4 I B Versus V BE Characteristic i B v be I BQ (1 ) VT I B i b
ac Equivalent Circuit for Common Emitter Neamen Microelectronics Chapter 6-5
Neamen Microelectronics Chapter 6-6 Small-Signal Hybrid p Model for npn BJT g r p g m m r p I V CQ T V I T CQ Phasor signals are shown in parentheses.
Small-Signal Equivalent Circuit Using Common-Emitter Current Gain Neamen Microelectronics Chapter 6-7
Neamen Microelectronics Chapter 6-8 Small-Signal Equivalent Circuit for npn Common Emitter circuit A v ( g m C )( r p r p B )
Neamen Microelectronics Chapter 6-9 Problem-Solving Technique: BJT AC Analysis 1. Analyze circuit with only dc sources to find Q point. 2. eplace each element in circuit with smallsignal model, including the hybrid p model for the transistor. 3. Analyze the small-signal equivalent circuit after setting dc source components to zero.
Neamen Microelectronics Chapter 6-10 Transformation of Elements Element DC Model AC Model esistor Capacitor Open C Inductor Short L Diode +V g, r f r d = V T /I D Independent Constant Voltage Source + V S - Short Independent Constant Current Source I S Open
Neamen Microelectronics Chapter 6-11 Hybrid p Model for npn with Early Effect r o V I A CQ
Hybrid p Model for pnp with Early Effect Neamen Microelectronics Chapter 6-12
Neamen Microelectronics Chapter 6-13
Neamen Microelectronics Chapter 6-14
Neamen Microelectronics Chapter 6-15
Neamen Microelectronics Chapter 6-16
Neamen Microelectronics Chapter 6-17
Neamen Microelectronics Chapter 6-18
Neamen Microelectronics Chapter 6-19
Neamen Microelectronics Chapter 6-20
Neamen Microelectronics Chapter 6-21
Neamen Microelectronics Chapter 6-22
Neamen Microelectronics Chapter 6-23
Neamen Microelectronics Chapter 6-24
Neamen Microelectronics Chapter 6-25
Neamen Microelectronics Chapter 6-26
Expanded Hybrid p Model for npn Neamen Microelectronics Chapter 6-27
Neamen Microelectronics Chapter 6-28 h-parameter Model for npn h h ie fe r b r p r h h re oe r r p 1 r 1 r o
T-Model of an npn BJT Neamen Microelectronics Chapter 6-29
Neamen Microelectronics Chapter 6-30 4 Equivalent 2-port Networks Voltage Amplifier Current Amplifier
Neamen Microelectronics Chapter 6-31 4 Equivalent 2-port Networks Transconductance Amplifier Transresistance Amplifier
Common Emitter with Voltage-Divider Bias and a Coupling Capacitor Neamen Microelectronics Chapter 6-32
Small-Signal Equivalent Circuit Coupling Capacitor Assumed a Short Neamen Microelectronics Chapter 6-33
npn Common Emitter with Emitter esistor Neamen Microelectronics Chapter 6-34
Neamen Microelectronics Chapter 6-35 Small-Signal Equivalent Circuit: Common Emitter with E ) ( ) (1 ) (1 2 1 S i i E C v ib i E ib r A r p p
E and Emitter Bypass Capacitor Neamen Microelectronics Chapter 6-36
Problem-Solving Technique: Maximum Symmetrical Swing 1. Write dc load line equation that relates I CQ and V CEQ. 2. Write ac load line equations that relates ic and vce 3. In general, i c = I CQ I C (min), where I C (min) is zero or other minimum collector current. 4. In general, v ce = V CEQ V CE (min), where V CE (min) is some specified minimum collector-emitter voltage. 5. Combine above 4 equations to find optimum I CQ and V CEQ. Neamen Microelectronics Chapter 6-37
Common-Collector or Emitter-Follower Amplifier Neamen Microelectronics Chapter 6-38
Neamen Microelectronics Chapter 6-39 Small-Signal Equivalent Circuit: Emitter Follower ) ( ) )( (1 ) )( (1 ) )( (1 2 1 S i i E o E o v ib i E o ib r r r A r r p p
Neamen Microelectronics Chapter 6-40 Output esistance: Emitter Follower o rp 1 E r o
Common-Base Amplifier Neamen Microelectronics Chapter 6-41
Neamen Microelectronics Chapter 6-42 Small-Signal Equivalent Circuit: Common Base A A v i g g m m ( ( C C C L ) L )[ 1 r p E ]
Neamen Microelectronics Chapter 6-43 Input esistance: Common Base ie = r p /(1+)
Neamen Microelectronics Chapter 6-44 Output esistance: Common Base O = C
Common Emitter Cascade Amplifier Neamen Microelectronics Chapter 6-45
Small-Signal Equivalent Circuit: Cascade Amplifier Neamen Microelectronics Chapter 6-46
Neamen Microelectronics Chapter 6-47 Darlington Pair A i 1 2
Cascode Amplifier Neamen Microelectronics Chapter 6-48
Neamen Microelectronics Chapter 6-49 Small-Signal Equivalent Circuit: Cascode Amplifier A g v ( m1 C L )