Lab 4 : Transistor Oscillators

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1 Objective: Lab 4 : Transistor Oscillators In this lab, you will learn how to design and implement a colpitts oscillator. In part II you will implement a RC phase shift oscillator Hardware Required : Pre lab: Resistors 470, 2.2k, 10k, 47k, 3.3k (4) Capacitors 50.7nF (2), 0.1μF(2), 0.01 μf(4) Inductor 0.1MH Transistor BC107 1 RPS (0.30 V) CRO 1 (i) (ii) Do the design of colpitts oscillator for a frequency fo=100khz. Do the design of RC phase shift oscillator for a frequency to = 2khz Part I: Colpitts oscillator Theory: The colpitts oscillator use tapped capacitance instead of tapped inductance used in Hartley oscillator. The tank circuit is made up of two capacitors C1 and C2 connected is series with each other across a fixed inductance (L) The feedback between the O/P & I/P circuit is accomplished by the voltage developed across the capacitor C2. The feedback fraction B = C 1 / C 2 For oscillation to start, the voltage gain (Av) must be greater I/B or (C 2 /C 1 ) Av> C 2 /C 1 The frequency of oscillation is given by the relation, fo= 1/2π L.C, where C= C 2.C 1 / C 2 +C 1 The capacitors C 1 and C 2 act as a simple alternating voltage divider. A total phase shift of 360 o between the emitter base and collector base circuits When the circuit is emerged by switching on the supply the capacitors C 1 and C 2 are charged. The capacitors discharge through the coil (L) which sets up the oscillations of the frequency f0 = 1/2π L.C. These oscillations across the capacitor C 2 are feedback to the base emitter junction and appear in an amplified form at the collector. Because of the positive feedback, the oscillations of constant amplitude are produced.

2 CKT Diagram: Test Procedure: 1. The circuit connections are made as shown in the circuit diagram 2. Setting Vcc = 10V the amplitude and frequency of the output waveform is noted 3. A graph of the output wave form is drawn Part II RC phase shift oscillator The feedback network consists of three identical RC sections. Each section produces a phase shift of 60 o Therefore, the net phase shift of the feedback is 180 o The amplifier stage introduces a phase shift of 180 o Therefore, the total phase shift between the input and output is 360 o or 0 o When the circuit is energized, by switching on the supply, the circuit starts oscillating. The oscillations will be maintained if the loop gain is at least equal to unity. Feed back fraction of the RC phase shift network =1/29 The frequency of oscillation f0=1/2 πrc 6. CIRCUIT DIAGRAM:

3 Test Procedure: 1. Connections are made as shown in the circuit diagram 2. The DC power supply is switched ON 3. The output waveform is displayed on the CRO 4. The peak to peak amplitude and time period of the sine wave is noted 5. The graph of output waveform is drawn Lab Result (i) (ii) Thus a colpitts oscillator is designed, constructed and tested Thus a RC phase shift oscillator is designed, constructed and tested Oscillator Theoretical frequency Practical frequency RC Phase shift Colpitts Questions: 1) Give the condition which determines the frequency of oscillation 2) How clap oscillator can be constructed from colpitts oscillator? 3) Sketch a diode amplitude stabilization circuit for a wein bridge oscillator and explain its operation 4) Explain the phase-shift principle in Lc oscillators? 5) Compare and contrast RC & LC oscillators 6) Where do you use IC oscillators?

4 Lab 2 : Transistor Amplifier Objective : In this lab you will learn how to design and implement a single stage CE amplifier. In part II you will implement current series feedback amplifier Hardware Required : Resistors 1.6k (4) 4k (2), 500 (2), Capacitors 10 μf(3), 250 μf(2) Transistor BC107 (2) RPS (0.30 V) CRO 1 Pre lab : Do the design of the single stage CE amplifier, with Ac=50, Vcc = 10V and Rc=500 Part I: CE amplifier: The common emitter amplifier is a small signal amplifier in which the resistance is used as a load, while the capacitor is used as an interstate coupling element. The coupling capacitor is also known as the blocking capacitor. It prevents the DC component of the output voltage from the first stage to enter the input of the second stage. Thus keeping the Q-point within the linear portion of the output characteristics of the device. In the CE amplifier the resistor connected to the base is used to establish the bias. The capacitor connected across the emitter resistance is used by pass to the ac component and it prevents the loss of amplification due to negative feedback. The bypass and the coupling capacitor affect the low frequency response of the amplifier. The high frequency response of the transistor is limited by the capacitance. Circuit Diagram :

5 Test Procedure: 1. Make connections as per the circuit diagram 2. Feed an input signal of 50mV amplitude 1000Hz frequency to the amplifier circuit. 3. Observe with an oscilloscope the input and output waveform. 4. Tabulate the measured output ac voltage calculate the voltage gain at 1KHz. Repeat the procedure for low, middle and high frequency regions starting from 50Hz to 1MHz. 5. Plot the voltage gain Vs frequency curve Note the values of Av, f L, f H, and 3 db bandwidth. Part II Current Series Feedback Amplifier The CE Amplifier with RE in the emitter lead is a good example for current series feedback amplifier Here, the voltage Vf across RE constitutes the feedback signed while the current Io forms sampled signal. Hence, these form a current series feedback. Thence, this form a current when compared to the connecter current using h parameter model for analysis purpose, the expressions for input impedance, output impedance, gain, bandwidth etc. can be calculated. For these, the following steps have to be followed. i) To find the output circuit, set Ii = 0 ie open the input loop thence RE appears also in output loop Hence, it is found that =Vf/Io = IoRE/Io = RE Also, Gm=Io/Vi Gm=Gm/D = Gm/1+ Gm Due to this negative feedback, though the gain is decreased, the stability is increased this is the advantage of negative feedback. Also improve the gain and stabilities, swamped resister us used. Circuit Diagram:

6 Test Procedure : Repeat the Part I test procedure for the current series feedback amplifier Lab result : (i) (ii) Thus a single stage CE amplifier is designed, constructed and tested Thus a current series feedback is designed constructed and tested Questions: 1. Identify the type of biasing circuit used in the amplifier and Justify its selection over other biasing circuits. 2. How the bypass and coupling capacitances affect the low frequency response of the amplifier? 3. From the experiment, compare the voltage gain and the Bandwidth of a CE amplifier and current series feedback amplifier. 4. How to construct a RC coupled amplifier using a single stage CE amplifier. 5. What do you understand by the term Negative feedback in amplifier 6. Design a JFET amplifier (CS)

7 SRM University Electronics and Communication Engineering ELECTRONIC CIRCUITS Laboratory Report Cover Sheet EC0222 EVEN SEM 2009 Name: Section: Circle One M ( ) TU () W ( ) Th ( ) Fr ( ) Venue: Title of Lab: Preparation Verification Staff Signature Score Completion Verification Staff Signature Date, Time Score Comments: Report Report Score

8 SRM University EC0222 Department of Electronics and Communication Engineering NAME: Lab 0 Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 OBJECTIVE (5 POINTS) EQUIPMENT & CIRCUIT DIAGRAM (10 POINTS) DESIGN (Pre lab) (30 POINTS) PROCEDURE TABULATION AND GRAPH (25 POINTS) ANSWERS (review questions) AND CONCLUSION (30 POINTS) TOTAL: (100 POINTS)

9 SRM University Electronics and Communication Engineering ELECTRONIC CIRCUITS Lab Report requirements EC0222 EVEN SEM 2009 The lab report should indicate your ability to present and discuss your results in a clear manner. It should contain the following sections. (i) (ii) (iii) (iv) (v) Objective: State clearly what your set out to achieve in this lab think abent it, interpret it, and explain it the best you can, in your own words. Parts: List the Hardware required for the experiment Design and Test Procedure: a) Give the necessary design and circuit diagram b) Step-by-step description of what you did. Include as many details as possible, and once again, write it in your own words. c) Give the necessary tabulation and calculations. Result and answers to questions. (i) Present your results in a clear and concise manner (label graph axes, include all units of measurement) (ii) Answer all the questions in the lab handout Conclusions: Give the conclusion in a clear and concise manner (i) What did you learn from this Lab? (ii) How could you have improved upon your design and test procedures? Grading Pre lab : 30 points Lab check off : 40 points Lab report : 30 points Total : 100 points

10 SRM UNIVERSITY FACULTY OF ENGINEERING AND TECHNOLOGY SCHOOL OF ELECTRICAL AND ELECTRONICS ENGINEERING DEPARTMENT OF ECE Course Code : EC0204 Course Title : Electronic circuits Year& Semester : II & IV semester Course Time : Even semester (Jan May 2009) Location : Tech Park (Room No.701, 702,703,704) Faculty Details: Name of the staff Section Office Office Hours Mail ID Mr.J.Selvakumar A MB:29 Monday( selva2802@yahoo.com 1.30 pm) Mrs.K.Suganthi B Tech park:703a Wed( pm) sugan_j@ece.srmuniv.ac.in Mr.A.V.M.Manikandan C MB:25 Wed(4-4.30, ) avm_mani@yahoo.com Ms.P.Radhika D Tech park:803a Wed( pm) radhikaselvam@yahoo.com Required Text Books: 1. Robert l. Boylsted,Louis Nashelsky, Electronic Devices and Circuit Theory,Pearson, Donald L.Schilling,Charles Belove Electronic circuits,3 rd edition David A Bell, Electronic Devices and Circuits, Prentice hall of India,1998. Prerequisite : EC0203, Electron Devices Objectives: 1. To learn the operating point calculations and working of basic amplifiers, various biasing Methods of BJT& FET 2. To learn the small signal equivalent model and its analysis of BJT, FET 3. To learn the working of different types of feedback amplifiers & oscillators. 4. To learn the power calculation of large signal amplifier and design of tuned amplifiers 5. To learn the frequency response of amplifier and basic working & design of wave shaping Circuits Tentative test dates Cycle test I : Surprise Test 1: - Cycle test II : Surprise Test 2: - Model Exam : Test Portions Cycle test I : Unit I and unit III Cycle test II : Unit II and Unit IV Model Exam : All five units Assessment details : Surprise test -15 marks, Cycle test I & II -10 marks each, Model Exam -15 marks

11 Outcomes Students who have successfully completed this course Course outcome Program outcome Operating point calculations and working of basic amplifiers. Working of different types of feedback amplifiers & oscillators. Frequency response and design of tuned amplifiers. Basic working & design of wave shaping circuits. Gains a thorough knowledge of the various types of feedback amplifiers,tuned amplifiers and oscillators with their applications. Also gains knowledge on various types of power amplifiers, wave shaping circuits and their analysis. Detailed Session Plan Sessi on 1 Unit-1:Biasing Methods and Small signal models Introduction about Electronic circuit 2 DC & AC load lines, Q point Electronic Device and circuit theory- Robert L.Boylestad(Ch:4) Topic Reference Testing Method Problem: page no Biasing methods: BJT Boylestad (Ch:4), Problem: page no Biasing methods: JFET Boylestad (Ch:7) Problem: page no Biasing methods: MOSFET Boylestad (Ch:7) Problem: page no Small signal equivalent Model Boylestad (Ch:5,8) 7 Small signal equivalent Model- Boylestad (Ch:5,8) Calculation of voltage gain, current gain, power gain 8 Calculation of Input Impedance, output impedance Boylestad (Ch:5,8) Problem( pg no 317) 9 Problems in Biasing Techniques Boylestad (Ch:5,8) Problem ( pg 10 Unit III: Feedback Amplifier and Oscillator Concept of Feedback and types of feedback Boylestad -Ch:14 11 Voltage feedback amplifier Boylestad -Ch:14 12 Current feedback amplifier Boylestad -Ch:14 no 170,172)

12 13 Analysis voltage feedback amplifier Boylestad -Ch:14 Problem: page no Analysis current feedback amplifier Boylestad -Ch:14 Problem: page no Oscillator: Barkhausen criterion Boylestad -Ch:14 and mechanism for oscillation 16 Analysis of RC phase shift oscillator Boylestad -Ch:14 Problem: page no Analysis of Wien Bridge oscillator Boylestad -Ch:14 Problem: page no Analysis of LC oscillator Boylestad -Ch:14 Problem: page no Unit II: Transistor Amplifier Boylestad-Ch 5 Problem: page no 249 And Analysis: Small signal analysis of BJT 20 Small signal analysis of JFET Boylestad-Ch 8 Problem: page no 491 Problem: page no Small signal analysis of MOSFET Boylestad-Ch 8 22 Cascade amplifier Boylestad-Ch 5 Problem: page no Cascode amplifier Boylestad-Ch 5 24 Darlington Bootstrap amplifier Boylestad-Ch 5 25 Differential amplifier Boylestad-Ch Unit IV: Large signal and Tuned amplifier Class A CE amplifier: Q point, Power calculation, maximum dissipation Hyperbola Electronic circuits-donald L.Schilling-Chapter 5 27 Transformer coupled amplifier Electronic circuits-donald L.Schilling-Chapter 5 28 Class B push pull amplifier Electronic circuits-donald L.Schilling-Chapter 5 29 Class AB Electron Devices and Circuits-David A Bell-Ch Direct coupled push pull amplifier 31 Amplifier using complementary symmetry, Heat sink Electron Devices and Circuits-David A Bell-Ch 18 Electronic circuits-donald L.Schilling-Chapter 5 Pspice Experiment in the lab 6 Pspice Experiment in the lab 6 Pspice Experiment in the lab 6 Pspice Experiment in the lab 6

13 32 Single Tuned amplifier Electronic circuits-donald L.Schilling-Chapter 9 Pspice Experiment in the lab 6 33 Double tuned & synchronously tuned amplifier Electronic circuits-donald L.Schilling-Chapter 9 34 Unit V: Frequency Response and Wave shaping circuits Boylestad -Ch:9 Problem:page no 553 Low frequency response BJT 35 Low frequency response JFET Boylestad -Ch:9 Problem:page no High frequency response BJT Boylestad -Ch:9 Problem:page no High frequency response -JFET Boylestad -Ch:9 Problem:page no Nonlinear Wave shaping circuits: Astable Multivibrator Applied Electronics- R.S.Sedha-Ch Monostable Multivibrator Applied Electronics- R.S.Sedha-Ch Bistable Multivibrator Applied Electronics- R.S.Sedha-Ch Schmitt trigger Applied Electronics- R.S.Sedha-Ch Time base generators Applied Electronics- R.S.Sedha-Ch 34 Pspice Experiment in the lab 6

SIDDHARTH GROUP OF INSTITUTIONS :: PUTTUR (AUTONOMOUS) Siddharth Nagar, Narayanavanam Road QUESTION BANK

SIDDHARTH GROUP OF INSTITUTIONS :: PUTTUR (AUTONOMOUS) Siddharth Nagar, Narayanavanam Road 517583 QUESTION BANK Subject with Code : Electronic Circuit Analysis (16EC407) Year & Sem: II-B.Tech & II-Sem