Electronic Circuits I
Total Page:16
File Type:pdf, Size:1020Kb
A Course Material on Electronic Circuits I By Mr. J.SHANMUGASUNDARAM ASSISTANT PROFESSOR DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING SASURIE COLLEGE OF ENGINEERING VIJAYAMANGALAM – 638 056 QUALITY CERTIFICATE This is to certify that the e-course material Subject Code : EC6304 Subject : Electronic Circuits I Class : II Year ECE Being prepared by me and it meets the knowledge requirement of the university curriculum. Signature of the Author Name : Mr. J. SHANMUGA SUNDARAM Designation: Assistant Professor This is to certify that the course material being prepared by Mr. J. SHANMUGA SUNDARAM is of adequate quality. He has referred more than five books among them minimum one is from abroad author. Signature of HD Name: Dr. K.PANDIARAJAN SEAL EC6304- ELECTRONIC CIRCUITS – I OBJECTIVES: The student should be made to • Learn about biasing of BJTs and MOSFETs • Design and construct amplifiers • Construct amplifiers with active loads • Study high frequency response of all amplifiers UNIT I - BIASING OF DISCRETE BJT AND MOSFET DC Load line, operating point, Various biasing methods for BJT-Design-Stability-Bias compensation, Thermal stability, Design of biasing for JFET, Design of biasing for MOSFET UNIT II - BJT AMPLIFIERS Small signal Analysis of Common Emitter-AC Loadline, Voltage swing limitations, Common collector and common base amplifiers – Differential amplifiers- CMRR- Darlington Amplifier- Bootstrap technique - Cascaded stages - Cascode Amplifier, UNIT III - JFET AND MOSFET AMPLIFIERS Small signal analysis of JFT amplifiers- Small signal Analysis of MOSFET and JFET, Common source amplifier, Voltage swing limitations, Small signal analysis of MOSFET and JFET Source follower and Common Gate amplifiers, - BiMOS Cascode amplifier UNIT IV - FREQUENCY ANALYSIS OF BJT AND MOSFET AMPLIFIERS Low frequency and Miller effect, High frequency analysis of CE and MOSFET CS amplifier, Short circuit current gain, cut off frequency – fα and fβ unity gain and Determination of bandwidth of single stage and multistage amplifiers UNIT V - IC MOSFET AMPLIFIERS IC Amplifiers- IC biasing Current steering circuit using MOSFET- MOSFET current sources- PMOS and NMOS current sources. Amplifier with active loads - enhancement load, Depletion load and PMOS and NMOS current sources load- CMOS common source and source follower- CMOS differential amplifier- CMRR. TOTAL (L: 45+T: 15): 60 PERIODS OUTCOMES: Upon Completion of the course, the students will be able to: • Design circuits with transistor biasing. • Design simple amplifier circuits. • Analyze the small signal equivalent circuits of transistors. • Design and analyze large signal amplifiers. TEXT BOOK: 1. Donald .A. Neamen, Electronic Circuit Analysis and Design –2nd Edition,Tata Mc Graw Hill, 2009. REFERENCES: 1. Adel .S. Sedra, Kenneth C. Smith, “Micro Electronic Circuits”, 6th Edition, Oxford University Press, 2010. 2. David A., “Bell Electronic Devices and Circuits”, Oxford Higher Education Press, 5th Editon, 2010 3. Behzad Razavi, “Design of Analog CMOS Integrated Circuits”, Tata Mc Graw Hill, 2007. 4. Paul Gray, Hurst, Lewis, Meyer “Analysis and Design of Analog Integrated Circuits”, 4thEdition ,John Willey & Sons 2005 5. Millman.J. and Halkias C.C, “Integrated Electronics”, Mc Graw Hill, 2001. 6. D.Schilling and C.Belove, “Electronic Circuits”, 3rd Edition, Mc Graw Hill, 1989. Sl.No Contents Page No UNIT 1 Biasing of Discrete BJT and MOSFET 1.1 Introduction 01 1.2 Need for Biasing 02 1.3 Load line and Variation of quiescent 02 point 1.4 Biasing Methods 09 1.5 Fixed Bias (Base Resistor Bias) 10 1.6 Requirements of a biasing circuit 14 1.7 Method of stabilizing the Q point 15 1.8 Stability Factors 15 1.9 Collector to Base Bias circuit 17 1.10 Modified collector to base bias circuit 18 1.11 Voltage divider bias circuit 20 1.12 Compensation technique 25 1.12.1 Diode Compensation Techniques 25 1.12.2 Thermistor Compensation 28 1.13 FET Biasing 30 1.14 Biasing of MOSFET 37 UNIT 2 BJT Amplifiers 2.1 Introduction 52 2.2 Common Emitter Amplifier 53 2.3 Common Collector Amplifier 54 2.4 Common Base Amplifier 54 2.5 Small Signal Low Frequency 55 H-parameter Model 2.6 h-Parameters for all three configurations 56 2.7 Midband analysis of BJT Single 59 Stage Amplifiers 2.8 Introduction of Differential 69 Amplifier 2.9 Transistorised Differential Amplifier 71 2.9.1 Differential Mode Operation 73 2.9.2 Common Mode Operation 74 2.10 Configurations of Differential 74 Amplifier 2.11 D.C. Analysis of Differential Amplifier 75 2.12 A.C. Analysis of Differential 77 Amplifier using h-Parameters 2.13 Common Mode rejection Ratio (CMRR) 81 2.14 Techniques of Improving Input Impedance 82 2.14.1 Darlington Transistors 82 2.14.2 Bootstrap Emitter Follower 87 UNIT 3 JFET and MOSFET Amplifiers 3.1 JFET Amplifiers 101 3.2 JFET low frequency a.c Equivalent 101 Circuit 3.3 Common Source Amplifier with Fixed Bias 101 3.4 Common Source Amplifier with Self Bias 102 (Bypassed Rs) 3.5 Common Source Amplifier with Self Bias 104 (Un bypassed Rs) 3.6 Common source amplifier with Voltage 105 divider bias (bypassed Rs) 3.7 Common source amplifier with Voltage 107 divider bias (unbypassed Rs) 3.8 Common Drain Amplifier 107 3.9 Common Gate Amplifier 110 3.10 Multistage Amplifiers 113 3.11 Small signal Analysis of MOSFET 115 3.12 Cascaded Amplifiers 119 UNIT 4 Frequency Analyses of BJT and MOSFET Amplifiers 4.1 General shape of frequency response 122 of Amplifiers 4.2 Definition of cut-off frequencies and 122 Bandwidth 4.3 Low frequency analysis of amplifier to 123 obtain lower cut-off frequency 4.4 Effect of various capacitors on 126 frequency response 4.5 Miller Theorem 126 4.6 Low frequency analysis of BJT 127 4.7 Low frequency analysis of FET 131 amplifier 4.8 Hybrid - π equivalent circuits of BJTs 133 4.9 High frequency analysis of FET 147 4.10 Frequency Response of Multistage 154 Amplifiers 4.11 Rise time and its Relation to Upper 156 Cut-off Frequency 4.12 Relation between Bandwidth and Rise time 158 UNIT 5 IC MOSFET Amplifiers 5.1 Integrated Circuit Amplifier 162 5.2 IC Design 162 5.3 Biasing - Basic MOSFET current 162 source 5.4 MOS current-steering circuits 163 5.5 NMOS Current Sources and Sinks 165 5.6 PMOS Current Source 166 5.7 MOSFET Differential amplifier 166 EC6304 Electronic Circuits I UNIT I BIASING OF DISCRETE BJT AND MOSFET 1.1 Introduction BJT consists of 2 PN junctions. It has three terminals: emitter, base and collector. Transistorcan be operated in three regions, namely cut-off, active and saturation by applying proper biasing conditions. Region of Operation Emitter Base Junction Collector Base Junction Cut-off Reverse biased Reverse biased Active Forward biased Reverse biased Saturation Forward biased Forward biased • Active: – Most important mode, e.g. for amplifier operation and switching application – The region where current curves are practically flat. • Saturation: – Barrier potential of the junctions cancels each other out causing a virtual short. – Ideal transistor behaves like a closed switch. • Cutoff: – Current reduced to zero – Ideal transistor behaves like an open switch. In order to operate transistor in the desired region we have to apply external d.c. voltages of correct polarity and magnitude to the two junctions of the transistor. This is nothing but the biasing of the transistor. When we bias a transistor we establish a certain current and voltage conditions for the transistor. These conditions are known as operating conditions or d.c. operating point or quiescent point. The operating point must be stable for proper operation of the transistor. However, the operating point shifts with changes in transistor parameters such as β, Ico and VBE. As transistor parameters are temperature dependent, the operating point also varies with changes in temperature. SCE 1 Dept of ECE EC6304 Electronic Circuits I 1.2 Need for biasing Fig.1.1 (a) Bias establishes the DC operating point for proper linear operation of an amplifier. If an amplifier is not biased with correct DC voltages on the input and output, it can go into saturation or cutoff when an input signal is applied. Figure 1.1 shows the effects of proper and improper DC biasing of an inverting amplifier. In part (a), the output signal is an amplified replica of the input signal except that it is inverted, which means that it is 1800 out of phase with the input. The output signal swings equally above and below the dc bias level of the output, VDC(out). Fig.1.1 (b), (c) Improper biasing can cause distortion in the output signal, as illustrated in parts (b) and (c). Part (b) illustrates limiting of the positive portion of the output voltage as a result of a Q- point (dc operating point) being too close to cutoff. Part (c) shows limiting of the negative portion of the output voltage as a result of a de operating point being too close to saturation. 1.3 Load line and Variation of quiescent point Biasing is the application of dc voltages to establish a fixed level of current and voltage. For transistor amplifiers the resulting dc current and voltage establish an operating point on the characteristics that define the region that will be employed for amplification of the applied signal. Since the operating point is a fixed point on the characteristics, it is also called the quiescent point (abbreviated Q-point). The operating point of a device, also known as bias SCE 2 Dept of ECE EC6304 Electronic Circuits I point, quiescent point, or Q-point, is the point on the output characteristics that shows the DC collector–emitter voltage (Vce) and the collector current (Ic) with no input signal applied. Consider the fixed bias circuit, Fig 1.2 We have, We can draw a straight line on the graph of IC versus VCE which is having slope -1/Rc.To determine the two points on the line we assume VCE = VCC and VCE =0 a) When VCE =VCC ; IC =0 and we get a point A b) When VCE=0 ; IC=VCC/RC and we get a point B The figure below shows the output characteristic curves for the transistor in CE mode.