Read Lab 4 : Transistor Oscillators text version

Lab 4 : Transistor Oscillators

Objective: 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 : Resistors Capacitors Inductor Transistor RPS CRO Pre lab: (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 470, 2.2k, 10k, 47k, 3.3k (4) 50.7nF (2), 0.1F(2), 0.01 F(4) 0.1MH BC107 1 (0.30 V) 1

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 = C1 / C2 For oscillation to start, the voltage gain (Av) must be greater I/B or (C2/C1) Av> C2/C1 The frequency of oscillation is given by the relation, fo= 1/2L.C , where C= C2.C1/ C2+C1 The capacitors C1 and C2 act as a simple alternating voltage divider. A total phase shift of 360o between the emitter base and collector base circuits When the circuit is emerged by switching on the supply the capacitors C1 and C2 are charged. The capacitors discharge through the coil (L) which sets up the oscillations of the frequency f0 = 1/2L.C. These oscillations across the capacitor C2 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.

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 60o 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 RC6. CIRCUIT DIAGRAM:

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 RC Phase shift Colpitts Theoretical frequency Practical frequency

Questions: 1) 2) 3) 4) 5) 6) Give the condition which determines the frequency of oscillation How clap oscillator can be constructed from colpitts oscillator? Sketch a diode amplitude stabilization circuit for a wein bridge oscillator and explain its operation Explain the phase-shift principle in Lc oscillators? Compare and contrast RC & LC oscillators Where do you use IC oscillators?

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 Capacitors Transistor RPS CRO Pre lab : Do the design of the single stage CE amplifier, with Ac=50, Vcc = 10V and Rc=500 1.6k(4) 4k(2), 500(2), 10 F(3), 250 F(2) BC107 (2) (0.30 V) 1

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 :

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, fL, fH, 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:

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)

SRM University Electronics and Communication Engineering


Laboratory Report Cover Sheet EC0222 Section: Circle One Name: ______________________________________ M() TU () W() Th ( ) EVEN SEM ­ 2009 Fr ( )

Venue: ________________________________________ Title of Lab: ________________________________________ __________________________________________________ Preparation Verification Staff Signature ______________________ Score _________________________ Completion Verification Staff Signature _______________________ Date, Time __________________________ Score ______________________________ Comments: ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________

Report Report Score ____________________________

SRM University Department of Electronics and Communication Engineering EC0222

NAME: ____________________________________________ Lab 0 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) Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6

SRM University Electronics and Communication Engineering


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) 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. (iv) Result and answers to questions. (i) (ii) (v) Present your results in a clear and concise manner (label graph axes, include all units of measurement) Answer all the questions in the lab handout Give the conclusion in a clear and concise manner (i) (ii) What did you learn from this Lab? How could you have improved upon your design and test procedures?


Grading Pre lab Lab check off Lab report Total : : : : 30 points 40 points 30 points 100 points

SRM UNIVERSITY FACULTY OF ENGINEERING AND TECHNOLOGY SCHOOL OF ELECTRICAL AND ELECTRONICS ENGINEERING DEPARTMENT OF ECE Course Code Course Title Year& Semester Course Time Location Faculty Details: Name of the staff Mr.J.Selvakumar : EC0204 : Electronic circuits : II & IV semester : Even semester (Jan ­ May 2009) : Tech Park (Room No.701, 702,703,704) Section Office A MB:29 Office Hours Mail ID

Monday(12.30- [email protected] 1.30 pm) Mrs.K.Suganthi B [email protected] Tech Wed(12.30park:703A 1.30 pm) Mr.A.V.M.Manikandan C MB:25 Wed(4-4.30, 1- [email protected] 1.30) Ms.P.Radhika D [email protected] Tech Wed(12.30park:803A 1.30 pm) Required Text Books: 1. Robert l. Boylsted,Louis Nashelsky,"Electronic Devices and Circuit Theory",Pearson , 1997. 2. Donald L.Schilling,Charles Belove" Electronic circuits",3rd edition.1989. 3. 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 : 25.2.09 Surprise Test 1: Cycle test II : 26.3.09 Surprise Test 2: Model Exam : 24.4.09 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

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 Topic on 1 Unit-1:Biasing Methods and Small signal models Introduction about Electronic circuit 2 DC & AC load lines, Q point 3 4 5 6 7 8 9 10 Biasing methods: BJT Biasing methods: JFET Biasing methods: MOSFET Small signal equivalent Model Small signal equivalent ModelCalculation of voltage gain, current gain, power gain Calculation of Input Impedance, output impedance Problems in Biasing Techniques Unit III: Feedback Amplifier and Oscillator Concept of Feedback and types of feedback Voltage feedback amplifier Current feedback amplifier


Testing Method

Electronic Device and circuit theory- Robert L.Boylestad(Ch:4) Boylestad (Ch:4), Boylestad (Ch:7) Boylestad (Ch:7) Boylestad (Ch:5,8) Boylestad (Ch:5,8) Boylestad (Ch:5,8) Boylestad (Ch:5,8) Boylestad -Ch:14

Problem: page no 184 Problem: page no 226 Problem: page no 410 Problem: page no 424

Problem( pg no 317) Problem ( pg no 170,172)

11 12

Boylestad -Ch:14 Boylestad -Ch:14

13 14 15 16 17 18 19 20 21 22 23 24 25 26

Analysis voltage feedback amplifier Analysis current feedback amplifier Oscillator: Barkhausen criterion and mechanism for oscillation Analysis of RC phase shift oscillator Analysis of Wien Bridge oscillator Analysis of LC oscillator

Boylestad -Ch:14 Boylestad -Ch:14 Boylestad -Ch:14 Boylestad -Ch:14 Boylestad -Ch:14 Boylestad -Ch:14 Boylestad-Ch 5 Boylestad-Ch 8 Boylestad-Ch 8 Boylestad-Ch 5 Boylestad-Ch 5 Boylestad-Ch 5 Boylestad-Ch 10

Problem: page no 747 Problem: page no 753 Problem: page no 760 Problem: page no 762 Problem: page no 774 Problem: page no 249 Problem: page no 491 Problem: page no 497 Problem: page no 507

Unit II: Transistor Amplifier And Analysis: Small signal analysis of BJT Small signal analysis of JFET Small signal analysis of MOSFET Cascade amplifier Cascode amplifier Darlington Bootstrap amplifier Differential amplifier Unit IV: Large signal and Tuned amplifier Class A CE amplifier: Q point, Power calculation, maximum dissipation Hyperbola Transformer coupled amplifier Class B push pull amplifier Class AB Direct coupled push pull amplifier Amplifier using complementary symmetry, Heat sink

Electronic circuits-Donald L.Schilling-Chapter 5 Electronic circuits-Donald L.Schilling-Chapter 5 Electronic circuits-Donald L.Schilling-Chapter 5 Electron Devices and Circuits-David A Bell-Ch 18 Electron Devices and Circuits-David A Bell-Ch 18 Electronic circuits-Donald L.Schilling-Chapter 5

27 28 29 30 31

Pspice Experiment in the lab 6 Pspice Experiment in the lab 6 Pspice Experiment in the lab 6 Pspice Experiment in the lab 6

32 33 34 35 36 37 38 39 40 41 42

Single Tuned amplifier Double tuned & synchronously tuned amplifier Unit V: Frequency Response and Wave shaping circuits Low frequency response ­BJT Low frequency response ­JFET High frequency response ­BJT High frequency response -JFET Nonlinear Wave shaping circuits: Astable Multivibrator Monostable Multivibrator Bistable Multivibrator Schmitt trigger Time base generators

Electronic circuits-Donald L.Schilling-Chapter 9 Electronic circuits-Donald L.Schilling-Chapter 9 Boylestad -Ch:9 Boylestad -Ch:9 Boylestad -Ch:9 Boylestad -Ch:9 Applied ElectronicsR.S.Sedha-Ch 32 Applied ElectronicsR.S.Sedha-Ch 32 Applied ElectronicsR.S.Sedha-Ch 32 Applied ElectronicsR.S.Sedha-Ch 32 Applied ElectronicsR.S.Sedha-Ch 34

Pspice Experiment in the lab 6 Problem:page no 553 Problem:page no 561 Problem:page no 571 Problem:page no 576 Pspice Experiment in the lab 6


Lab 4 : Transistor Oscillators

13 pages

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