UNIT - 1 i SYLLABUS OSMANIA UNIVERSITY (HYDERABAD) JUNCTION DIODE Different Types of PN Junction Formation Techniques, PN Junction Characteristics, Biasing, Band Diagrams and Current Flow, Diode Current Equations, Breakdown Voltages, Effect of Temperature on Diode Characteristics, Diode as a Circuit Element, Small Signal Diode Models, Junction Capacitance under Forward Bias and Reverse Bias, Diode Switching Characteristics, Zener Diodes, Zener Voltage Regulator and Its Limitation. UNIT - 2 PN DIODE APPLICATIONS Half Wave, Full Wave and Bridge Rectifiers, Their Operation, Performance Characteristics, and Analysis, Filters (L, C, LC and CLC Filters) Used in Power Supplies and their Ripple Factor Calculations, Design of Rectifiers with and without Filters. Special Diodes : Elementary Treatment on the Functioning of Tunnel/Back Ward, Varactor, Photo, Light Emitting Diodes, Liquid Crystal Display. CRO : Study of Block Diagram of CRO. UNIT - 3 BIPOLAR JUNCTION TRANSISTOR Transistor Junction Formation (Collector-base, Base-emitter Junctions), Transistor Biasing, Band Diagram for NPN and PNP Transistors, Current Components and Current Flow in BJT, Modes of Transistor Operation, Early Effect, BJT Biasing Techniques, Thermal Runaway, Heat Sinks and Thermal Stabilization, Operating Point stabilization Against Temperature and Device Variations, Stability Factors, Bias Stabilization and Compensation Techniques, Biasing Circuit Design.
UNIT - 4 ii SMALL SIGNAL TRANSISTORS EQUIVALENT CIRCUITS Small Signal Low Frequency h-parameter Model of BJT, Determination of h- Parameters, Analysis of BJT Amplifiers Using h-parameter, Comparison of CB, CE and CC Amplifier Configurations, Analysis of BJT Amplifier with Approximate Model, Introduction to Low Frequency r e and T Models. Special Devices, Working of UJT, SCR, DIAC, TRIAC and CCD. UNIT - 5 JUNCTION FIELD EFFECT TRANSISTORS (JFET) JFET Formation, Operation and Current Flow, Pinch-off Voltage, V-I Characteristics of JFET. JFET Biasing-zero Current Drift Biasing, Biasing Against Device Variations. Low Frequency Small Signal Model of FETs. Analysis of CS, CD and CG Amplifiers and their Comparison. FET as an Amplifier and as a Switch. MOSFETs : Enhancement and Depletion Mode MOSFETs, V-I Characteristics, MOSFET as Resistance, Biasing of MOSFETs, MOSFET as a Switch.
iii CONTENTS UNIT - 1 [JUNCTION DIODE]... 1.1-1.50 1.1 INTRODUCTION... 1.2 1.2 DIFFERENT TYPES OF PN JUNCTION FORMATION TECHNIQUES... 1.2 1.2.1 Grown Junction... 1.2 1.2.2 Alloy Junction... 1.3 1.2.3 Diffused Junction... 1.4 1.3 QUALIT ALITATIVE TIVE THEORY OF PN JUNCTION DIODE... 1.5 1.4 BIASING... 1.7 1.4.1 Forward Biasing... 1.7 1.4.2 Reverse Biasing... 1.9 1.5 BAND DIAGRAMS OF PN JUNCTION DIODE... 1.10 1.5.1 Energy Band Diagram of Open-Circuited P-N -N Junction... 1.10 1.5.2 Energy Band Diagram of Reverse Biased P-N -N Junction... 1.15 1.5.3 Energy Band Diagram of Forward Biased P-N -N Junction... 1.15 1.6 CURRENT FLOW IN PN JUNCTION DIODE... 1.15 1.7 DIODE CURRENT EQUATIONS UNDER FORWARD BIAS AND REVERSE BIAS CONDITIONS... 1.17 1.7.1 Derivation of Diode Equation... 1.19 1.8 PN JUNCTION CHARACTERISTICS... 1.21 1.8.1 V-I Characteristics of Forward Bias... 1.22 1.8.2 V-I Characteristics of Reverse Bias... 1.22 1.9 EFFECT OF TEMPERATURE TURE ON DIODE CHARACTERISTICS CTERISTICS... 1.23 1.9.1 Effect of Temperature on Reverse Saturation Current... 1.23 1.9.2 Effect of Temperature on Barrier Potential... 1.24
iv 1.10 JUNCTION BREAKDOWN IN DIODES AND BREAK DOWN VOL OLTAGES... 1.26 1.10.1 Zener Breakdown... 1.27 1.10.2 Avalanche Breakdown... 1.28 1.10.3 Comparison of Breakdown Mechanisms... 1.29 1.10.4 Temperature Dependence of Breakdown Voltages... 1.30 1.11 DIODE AS A CIRCUIT ELEMENT... 1.30 1.12 SMALL SIGNAL DIODE MODELS... 1.33 1.13 JUNCTION CAPACIT CITANCE UNDER FORWARD BIAS AND REVERSE BIAS... 1.35 1.13.1 Transition capacitance (C T )... 1.35 1.13.1.1 Transition Capacitance in Step Graded Junction... 1.36 1.13.1.2 Transition Capacitance in Linear Graded Junction... 1.39 1.13.2 Diffusion Capacitance (C D )... 1.39 1.14 DIODE SWITCHING CHARACTERISTICS... 1.42 1.15 ZENER DIODES... 1.44 1.15.1 Zener Characteristics... 1.45 1.15.2 Equivalent Circuit of Zener Diode... 1.45 1.15.3 Comparison of PN Junction and Zener Diode... 1.46 1.16 ZENER VOL OLTAGE REGULATOR... 1.47 1.16.1 Regulation with Varying Input Voltage (Line Regulation) egulation)... 1.47 1.16.2 Regulation with Varying Load Resistance (Load Regulation)... 1.48 1.16.3 Zener Voltage Regulator Limitations... 1.50
v UNIT - 2 [PN DIODE APPLICATIONS]... 2.1-2.74 2.1 THE P-N JUNCTION AS A RECTIFIER... 2.2 2.2 HALF WAVE RECTIFIERS... 2.4 2.2.1 Working Operation... 2.5 2.2.2 Performance Characteristics and Analysis of Half-wave Rectifier... 2.5 2.2.2.1 Rectifier Efficiency (η)... 2.9 2.2.2.2 Ripple Factor... 2.9 2.2.2.3 Transformer Utilization Factor (TUF)... 2.11 2.2.2.4 Voltage Regulation egulation... 2.13 2.2.3 Peak Inverse Voltage (PIV)... 2.14 2.2.4 Advantages of a Half-wave Rectifier... 2.14 2.2.5 Disadvantages of a Half-wave Rectifier... 2.14 2.3 FULL WAVE AND BRIDGE RECTIFIERS... 2.17 2.3.1 Center Tapped Rectifier... 2.17 2.3.1.1 Working Operation... 2.17 2.3.1.2 Voltage and Current Waveforms of a FWR... 2.19 2.3.1.3 Performance Characteristics and Analysis of a Center Tapped FWR... 2.20 2.3.1.4 Peak Inverse Voltage... 2.26 2.3.1.5 Advantages... 2.26 2.3.1.6 Disadvantages... 2.26 2.3.2 Bridge Rectifier... 2.28 2.3.2.1 Working Operation... 2.29
vi 2.3.2.2 Performance Characteristics and Analysis of Full Wave Bridge Rectifier... 2.30 2.3.2.3 Peak Inverse Voltage... 2.32 2.3.2.4 Why Bridge Rectifier is Preferred?... 2.33 2.4 FILTERS (L,, C, LC AND CLC FILTERS) USED IN POWER SUPPLIES... 2.34 2.4.1 Inductor Filters (L-Filters)... 2.35 2.4.1.1 Working Operation... 2.36 2.4.1.2 Ripple Factor Calculation... 2.37 2.4.1.3 Disadvantages of Inductor Filter... 2.40 2.4.2 Capacitor Filters (C-Filters)... 2.40 2.4.2.1 Working Operation... 2.41 2.4.2.2 Ripple Factor Calculation... 2.42 2.4.2.3 Advantages and Disadvantages... 2.44 2.4.3 LC Filters or L-Section Filters... 2.44 2.4.3.1 Working Operation... 2.45 2.4.3.2 Ripple Factor Calculation... 2.46 2.4.3.3 Advantages and Disadvantages... 2.48 2.4.4 CLC Filters or π - Section Filters... 2.48 2.4.4.1 Working Operation... 2.48 2.4.4.2 Ripple Factor Calculation... 2.49 2.4.4.3 Advantages and Disadvantages... 2.50 2.4.4.4 Comparison of L-section and π-section Filters... 2.50 2.5 DESIGN OF RECTIFIERS WITH AND WITHOUT FILTERS TERS... 2.51 2.6 SPECIAL DIODES... 2.52 2.6.1 Elementary Treatment on the Functioning of Tunnel/Backward Diode... 2.52
vii 2.6.1.1 Explanation of V-I Characteristics Using Energy Band Diagrams... 2.53 2.6.2 Varactor Diode... 2.56 2.6.2.1 Construction... 2.57 2.6.2.2 Reverse Biased P-N Junction as a Varactor Diode... 2.57 2.6.3 Photo Diode... 2.59 2.6.3.1 Construction... 2.59 2.6.3.2 Principle of Operation... 2.60 2.6.3.3 Biasing... 2.60 2.6.3.4 Photodiode Characteristics... 2.61 2.6.4 Light Emitting Diodes... 2.62 2.6.4.1 Construction... 2.2 2.6.4.2 Light Generating Mechanism in LEDs... 2.63 2.6.4.3 Light Source Materials... 2.64 2.6.4.4 Circuit Symbol... 2.64 2.6.4.5 LED Voltage Drop and Current... 2.64 2.6.4.6 Characteristics of LED... 2.65 2.6.4.7 Advantages and Disadvantages... 2.66 2.6.4.8 Comparison of PN-Junction Diode and LED... 2.67 2.6.5 Liquid Crystal Display... 2.67 2.7 CATHODE RAY OSCILLOSCOPE OSCOPE (CRO)... 2.70 2.7.1 Study of Block Diagram of CRO... 2.71 2.7.2 Applications of CRO... 2.72
viii UNIT - 3 [BIPOLAR JUNCTION TRANSISTOR]... 3.1-3.80 3.1 INTRODUCTION TO TRANSISTOR... 3.2 3.2 TRANSISTOR JUNCTION FORMATION (COLLECTOR OR-BASE -BASE,, BASE-EMITTER JUNCTIONS)... 3.2 3.2.1 Transistor Terminals erminals... 3.3 3.2.2 BJT Symbols and Conventions... 3.4 3.3 BAND DIAGRAM FOR NPN AND PNP TRANSISTORS ORS... 3.5 3.4 TRANSISTOR ACTION... 3.6 3.4.1 Unbiased Transistor ransistor... 3.6 3.4.2 Biased Transistor... 3.6 3.4.3 Working operation of NPN transistor... 3.7 3.4.4 Working Operation of PNP Transistor ransistor... 3.8 3.5 CURRENT COMPONENTS AND CURRENT FLOW IN BJT... 3.9 3.5.1 Emitter Efficiency (γ)... 3.10 3.5.2 Transport Factor (β)... 3.10 3.5.3 Large Signal Current Gain (α)... 3.11 3.5.4 Generalized Expression for Collector Current... 3.11 3.6 MODES OF TRANSISTOR OR OPERATION... 3.13 3.7 EARLY Y EFFECT OR BASE WIDTH MODULATION TION... 3.15 3.8 BJT INPUT AND OUTPUT CHARACTERISTICS... 3.16 3.8.1 BJT Characteristics in CB Configuration... 3.16 3.8.1.1 Input Characteristics... 3.16 3.8.1.2 Output Characteristics... 3.17 3.8.2 BJT Characteristics in CE Configuration... 3.18 3.8.2.1 Input Characteristics... 3.19 3.8.2.2 Output Characteristics... 3.20
ix 3.8.3 BJT Characteristics in CC Configuration... 3.23 3.8.3.1 Input Characteristics... 3.23 3.8.3.2 Output Characteristics... 3.24 3.8.4 Commonly used Transistor Configuration... 3.25 3.9 BJT AS AN AMPLIFIER... 3.25 3.10 TRANSISTOR BIASING... 3.28 3.10.1 Need for Transistor Biasing... 3.28 3.10.2 Selection of the Operating Point... 3.29 3.11 BIAS STABILIZA ABILIZATION... 3.32 3.11.1 Causes of Unstabilization... 3.32 3.11.1.1 Temperature Dependence of Collector Current... 3.32 3.11.1.2 Effect of Inherent Variations of Parameters... 3.33 3.11.2 Methods of Achieving Q-point Stability... 3.33 3.12 STABILITY FACT CTOR OR... 3.34 3.12.1 General Expression of Stability Factor actor,, S... 3.34 3.12.2 Other Stability Factors (S' and S")... 3.34 3.12.2.1 Stability Factor (S')... 3.35 3.12.2.2 Stability Factor (S")... 3.35 3.12.3 General Guidelines to Evaluate Expressions for Stability Factors... 3.36 3.13 BJT BIASING TECHNIQUES... 3.36 3.13.1 Fixed Bias... 3.37 3.13.1.1 D.C. Analysis... 3.37 3.13.1.2 Stability Factors... 3.39 3.13.1.3 Advantages and Disadvantages of Fixed-Biasing... 3.41
x 3.13.2 Collector to Base Bias... 3.41 3.13.2.1 D.C Analysis... 3.42 3.13.2.2 Stabilization Against Variation of Temperature and β... 3.43 3.13.2.3 Stability Factors... 3.44 3.13.3 Emitter-Feedback Bias... 3.47 3.13.3.1 D.C Analysis... 3.48 3.13.3.2 Stabilization Against Temperature and Device Variations... 3.52 3.13.3.3 Stability Factors... 3.53 3.13.3.4 Advantages and Disadvantages... 3.53 3.13.4 Self-Bias (or) Voltage oltage-divider Bias... 3.55 3.13.4.1 D.C.C Analysis... 3.55 3.13.4.2 Stabilization Against Variation of Temperature and β... 3.59 3.13.4.3 Stability Factors... 3.59 3.13.4.4 Advantages... 3.63 3.13.4.5 Why the Voltage oltage-divider Biasing Circuit is Most Widely Used... 3.63 3.13.5 Comparison of BJT Biasing Techniques... 3.64 3.14 BIAS COMPENSATION TECHNIQUES... 3.64 3.14.1 Diode Compensation for Instability Due to V BE Variation... 3.65 3.14.2 Diode Compensation for Instability Due to I CO Variation... 3.66 3.14.3 Thermistor Compensation... 3.67 3.14.4 Sensistor Compensation... 3.68 3.15 BIASING CIRCUIT DESIGN... 3.68
xi 3.16 THERMAL RUNAWAY... 3.74 3.16.1 Heat Sinks... 3.75 3.16.2 Thermal Resistance... 3.76 3.16.3 Thermal Stabilization... 3.77 UNIT - 4 [SMALL SIGNAL TRANSISTORS EQUIVALENT CIRCUITS]... 4.1-4.52 4.1 SMALL SIGNAL LOW FREQUENCY H-PARAMETER MODEL OF BJT... 4.2 4.1.1 Hybrid Parameter Model... 4.2 4.1.2 Transistor Hybrid Model... 4.5 4.2 DETERMINATION TION OF H-PARAMETERS ARAMETERS... 4.7 4.2.1 Determination of h fe oe from Output Characteristics... 4.7 4.2.2 Determination of h ie re from Input Characteristics... 4.8 4.3 ANALYSIS OF BJT AMPLIFIERS USING H-PARAMETER ARAMETER... 4.10 4.4 COMPARISON OF CB,, CE AND CC AMPLIFIER CONFIGURATIONS TIONS... 4.17 4.5 ANALYSIS OF BJT AMPLIFIER WITH APPROXIMA XIMATE TE MODEL... 4.18 4.5.1 Analysis of CE Amplifier Using Approximate h-model... 4.19 4.5.2 Analysis of CB Amplifier Using Approximate h-model... 4.23 4.5.3 Analysis of CC Amplifier Using Approximate h-model... 4.25 4.5.4 Formulae for Transistor Configuration Using... Exact and Simplified h-models... 4.29 4.6 INTRODUCTION TO LOW FREQUENCY r e AND T MODELS... 4.29 4.6.1 Analysis of CE Amplifier using r e Model... 4.33 4.6.2 T-Model... 4.34 4.7 SPECIAL DEVICES... 4.35 4.7.1 UJT... 4.35 4.7.1.1 Construction of UJT... 4.35
xii 4.7.1.2 Equivalent Circuit... 4.36 4.7.1.3 Principle of Operation... 4.37 4.7.1.4 UJT Characteristics... 4.38 4.7.2 SCR... 4.40 4.7.2.1 Working Operation... 4.40 4.7.2.2 Two Transistor Analogy of SCR... 4.42 4.7.2.3 V-I Characteristics of SCR... 4.45 4.7.3 TRIAC... 4.45 4.7.3.1 Triac Construction... 4.46 4.7.3.2 Triac Operation... 4.47 4.7.3.3 Triac Characteristics... 4.48 4.7.4 DIAC... 4.49 4.7.5 Charge Coupled Devices... 4.50 UNIT - 5 [JUNCTION FIELD EFFECT TRANSISTORS (JFET)]... 5.1-5.54 5.1 INTRODUCTION... 5.2 5.2 JFET FORMATION... 5.2 5.3 OPERATION AND CURRENT FLOW OW... 5.3 5.4 PINCH-OFF VOL OLTAGE... 5.6 5.5 V-I -I CHARACTERISTICS CTERISTICS OF JFET... 5.8 5.5.1 Drain Characteristics... 5.8 5.5.2 Transfer Characteristics... 5.12 5.6 JFET BIASING... 5.16 5.6.1 Zero Current Drift Biasing... 5.17 5.6.2 Biasing Against Device Variation... 5.20 5.7 JFET PARAMETERS... 5.20 5.7.1 A.C Drain Resistance... 5.20
xiii 5.7.2 Transconductance... 5.21 5.7.3 Amplification Factor... 5.23 5.7.4 Relation Between r, g d m and μ... 5.23 5.8 LOW FREQUENCY SMALL SIGNAL MODEL OF FETs... 5.24 5.9 FET AS AN AMPLIFIER... 5.25 5.10 ANALYSIS OF CS,, CD AND CG AMPLIFIERS... 5.26 5.10.1 Common Source Amplifier... 5.26 5.10.1.1 Common Source Amplifier with Bypassed Source Resistance... 5.26 5.10.1.2 Common Source Amplifier with Unbypassed Source Resistance... 5.31 5.10.2 Common Drain Amplifier... 5.33 5.10.3 Common Gate Amplifier... 5.40 5.10.4 Comparison of CS, CD and CG Amplifier... 5.42 5.11 FET AS A SWITCH... 5.42 5.12 MOSFETS... 5.42 5.12.1 Depletion Mode MOSFETs s (DE-MOSFET -MOSFETs) s)... 5.43 5.12.1.1 Construction... 5.43 5.12.1.2 Working Operation... 5.43 5.12.2 Enhancement Mode MOSFETs s (E-MOSFET -MOSFETs) s)... 5.45 5.12.2.1 Construction... 5.45 5.12.2.2 Working Operation... 5.45 5.12.3 MOSFET V-I Characteristics... 5.46 5.12.3.1 Drain Characteristics of DE-MOSFET... 5.46 5.12.3.2 Transfer Characteristics of DE-MOSFET... 5.48 5.12.3.3 Drain Characteristics of E-MOSFET... 5.49 5.12.3.4 Transfer Characteristics of E-MOSFET... 5.49
xiv 5.12.4 MOSFET As Resistance... 5.50 5.12.5 BIASING OF MOSFETs... 5.51 5.12.5.1 Biasing of Enhancement MOSFET... 5.51 5.12.5.2 Biasing of Depletion MOSFET... 5.53 5.12.6 MOSFET as a Switch... 5.53 EXPECTED UNIVERSITY QUESTIONS Expected University Questions with Solutions... E.1 - E.14