INSTITUTION Controlledoscillators. Each Lesson Follows a Typical
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Chapter 19 - the Oscillator
Chapter 19 - The Oscillator The Electronics Curse “Your amplifiers will oscillate, your oscillators won't!” Question, What is an Oscillator? A Pendulum is an Oscillator... “Oscillators are circuits that are used to generate A.C. signals. Although mechanical methods, like alternators, can be used to generate low frequency A.C. signals, such as the 50 Hz mains, electronic circuits are the most practical way of generating signals at radio frequencies.” Comment: Hmm, wasn't always. In the time of Marconi, generators were used to generate a frequency to transmit. We are talking about kiloWatts of power! e.g. Grimeton L.F. Transmitter. Oscillators are widely used in both transmitters and receivers. In transmitters they are used to generate the radio frequency signal that will ultimately be applied to the antenna, causing it to transmit. In receivers, oscillators are widely used in conjunction with mixers (a circuit that will be covered in a later module) to change the frequency of the received radio signal. Principal of Operation The diagram below is a ‘block diagram’ showing a typical oscillator. Block diagrams differ from the circuit diagrams that we have used so far in that they do not show every component in the circuit individually. Instead they show complete functional blocks – for example, amplifiers and filters – as just one symbol in the diagram. They are useful because they allow us to get a high level overview of how a circuit or system functions without having to show every individual component. The Barkhausen Criterion [That's NOT ‘dog box’ in German!] Comment: In electronics, the Barkhausen stability criterion is a mathematical condition to determine when a linear electronic circuit will oscillate. -
AM Transmitters
Chapter 4: AM Transmitters Chapter 4 Objectives At the conclusion of this chapter, the reader will be able to: • Draw a block diagram of a high or low-level AM transmitter, giving typical signals at each point in the circuit. • Discuss the relative advantages and disadvantages of high and low-level AM transmitters. • Identify an RF oscillator configuration, pointing out the components that control its frequency. • Describe the physical construction of a quartz crystal. • Calculate the series and parallel resonant frequencies of a quartz crystal, given manufacturer's data. • Identify the resonance modes of a quartz crystal in typical RF oscillator circuits. • Describe the operating characteristics of an RF amplifier circuit, given its schematic diagram. • Explain the operation of modulator circuits. • Identify the functional blocks (amplifiers, oscillators, etc) in a schematic diagram. • List measurement procedures used with AM transmitters. • Develop a plan for troubleshooting a transmitter. In Chapter 3 we studied the theory of amplitude modulation, but we never actually built an AM transmitter. To construct a working transmitter (or receiver), a knowledge of RF circuit principles is necessary. A complete transmitter consists of many different stages and hundreds of electronic components. When beginning technicians see the schematic diagram of a "real" electronic system for the first time, they're overwhelmed. A schematic contains much valuable information. But to the novice, it's a swirling mass of resistors, capacitors, coils, transistors, and IC chips, all connected in a massive web of wires! How can anyone understand this? All electronic systems, no matter how complex, are built from functional blocks or stages. -
Oscillator Design
Oscillator Design •Introduction –What makes an oscillator? •Types of oscillators –Fixed frequency or voltage controlled oscillator –LC resonator –Ring Oscillator –Crystal resonator •Design of oscillators –Frequency control, stability –Amplitude limits –Buffered output –isolation –Bias circuits –Voltage control –Phase noise 1 Oscillator Requirements •Power source •Frequency-determining components •Active device to provide gain •Positive feedback LC Oscillator fr = 1/ 2p LC Hartley Crystal Colpitts Clapp RC Wien-Bridge Ring 2 Feedback Model for oscillators x A(jw) i xo A (jw) = A f 1 - A(jω)×b(jω) x = x + x d i f Barkhausen criteria x f A( jw)× b ( jω) =1 β Barkhausen’scriteria is necessary but not sufficient. If the phase shift around the loop is equal to 360o at zero frequency and the loop gain is sufficient, the circuit latches up rather than oscillate. To stabilize the frequency, a frequency-selective network is added and is named as resonator. Automatic level control needed to stabilize magnitude 3 General amplitude control •One thought is to detect oscillator amplitude, and then adjust Gm so that it equals a desired value •By using feedback, we can precisely achieve GmRp= 1 •Issues •Complex, requires power, and adds noise 4 Leveraging Amplifier Nonlinearity as Feedback •Practical trans-conductance amplifiers have saturating characteristics –Harmonics created, but filtered out by resonator –Our interest is in the relationship between the input and the fundamental of the output •As input amplitude is increased –Effective gain from input -
Lec#12: Sine Wave Oscillators
Integrated Technical Education Cluster Banna - At AlAmeeria © Ahmad El J-601-1448 Electronic Principals Lecture #12 Sine wave oscillators Instructor: Dr. Ahmad El-Banna 2015 January Banna Agenda - © Ahmad El Introduction Feedback Oscillators Oscillators with RC Feedback Circuits 1448 Lec#12 , Jan, 2015 Oscillators with LC Feedback Circuits - 601 - J Crystal-Controlled Oscillators 2 INTRODUCTION 3 J-601-1448 , Lec#12 , Jan 2015 © Ahmad El-Banna Banna Introduction - • An oscillator is a circuit that produces a periodic waveform on its output with only the dc supply voltage as an input. © Ahmad El • The output voltage can be either sinusoidal or non sinusoidal, depending on the type of oscillator. • Two major classifications for oscillators are feedback oscillators and relaxation oscillators. o an oscillator converts electrical energy from the dc power supply to periodic waveforms. 1448 Lec#12 , Jan, 2015 - 601 - J 4 FEEDBACK OSCILLATORS FEEDBACK 5 J-601-1448 , Lec#12 , Jan 2015 © Ahmad El-Banna Banna Positive feedback - • Positive feedback is characterized by the condition wherein a portion of the output voltage of an amplifier is fed © Ahmad El back to the input with no net phase shift, resulting in a reinforcement of the output signal. Basic elements of a feedback oscillator. 1448 Lec#12 , Jan, 2015 - 601 - J 6 Banna Conditions for Oscillation - • Two conditions: © Ahmad El 1. The phase shift around the feedback loop must be effectively 0°. 2. The voltage gain, Acl around the closed feedback loop (loop gain) must equal 1 (unity). 1448 Lec#12 , Jan, 2015 - 601 - J 7 Banna Start-Up Conditions - • For oscillation to begin, the voltage gain around the positive feedback loop must be greater than 1 so that the amplitude of the output can build up to a desired level. -
TRANSIENT STABILITY of the WIEN BRIDGE OSCILLATOR I
TRANSIENT STABILITY OF THE WIEN BRIDGE OSCILLATOR i TRANSIENT STABILITY OF THE WIEN BRIDGE OSCILLATOR by RICHARD PRESCOTT SKILLEN, B. Eng. A Thesis Submitted ··to the Faculty of Graduate Studies in Partial Fulfilment of the Requirements for the Degree Master of Engineering McMaster University May 1964 ii MASTER OF ENGINEERING McMASTER UNIVERSITY (Electrical Engineering) Hamilton, Ontario TITLE: Transient Stability of the Wien Bridge Oscillator AUTHOR: Richard Prescott Skillen, B. Eng., (McMaster University) NUMBER OF PAGES: 105 SCOPE AND CONTENTS: In many Resistance-Capacitance Oscillators the oscillation amplitude is controlled by the use of a temperature-dependent resistor incorporated in the negative feedback loop. The use of thermistors and tungsten lamps is discussed and an approximate analysis is presented for the behaviour of the tungsten lamp. The result is applied in an analysis of the familiar Wien Bridge Oscillator both for the presence of a linear circuit and a cubic nonlinearity. The linear analysis leads to a highly unstable transient response which is uncommon to most oscillators. The inclusion of the slight cubic nonlinearity, however, leads to a result which is in close agreement to the observed response. ACKNOWLEDGEMENTS: The author wishes to express his appreciation to his supervisor, Dr. A.S. Gladwin, Chairman of the Department of Electrical Engineering for his time and assistance during the research work and preparation of the thesis. The author would also like to thank Dr. Gladwin and all his other undergraduate professors for encouragement and instruction in the field of circuit theor.y. Acknowledgement is also made for the generous financial support of the thesis project by the Defence Research Board·under grant No. -
Spectrum Analyzer Circuits 062-1055-00
Circuit Concepts BOOKS IN THIS SERIES: Circuit Concepts Power Supply Circuits 062-0888-01 Oscilloscope Cathode-Ray Tubes 062-0852-01 Storage Cathode-Ray Tubes and Circuits 062-0861-01 Television Waveform Processing Circuits 062-0955-00 Digital Concepts 062-1030-00 Spectrum Analyzer Circuits 062-1055-00 Oscilloscope Trigger Circuits 062-1056-00 Sweep Generator Circuits 062-1098-00 Measurement Concepts Information Display Concepts 062-1005-00 Semiconductor Devices 062-1009-00 Television System Measurements 062-1064-00 Spectrum Analyzer Measurements 062-1070-00 Engine Analysis 062-1074-00 Automated Testing Systems 062-1106-00 SPECTRUM ANALYZER CIRCUITS BY MORRIS ENGELSON Significant Contributions by GORDON LONG WILL MARSH CIRCUIT CONCEPTS FIRST EDITION, SECOND PRINTING, AUGUST 1969 062-1055-00 ©TEKTRONIX, INC.; 1969 BEAVERTON, OREGON 97005 ALL RIGHTS RESERVED CONTENTS 1 BACKGROUND MATERIAL 1 2 COMPONENTS AND SUBASSEMBLIES 23 3 FILTERS 55 4 AMPLI FI'ERS 83 5 MIXERS 99 6 OSCILLATORS 121 7 RF ATTENNATORS 157 BIBLIOGRAPHY 171 INDEX 175 1 BACKGROUND MATERIAL Many spectrum analyzer circuits are based on principles with which most engineers may not be familiar. It is the purpose of this chapter to review some of this specialized background material. This review is not intended to be either complete or rigorous. Those desiring a more complete discussion are referred to the basic references and the bibliography. TRANSMISSION LINES* At low frequencies the basic circuit elements are lumped. At higher frequencies, however, where the size of circuit elements is comparable to a wavelength, lumped elements can not be used easily, if at all. This accounts for the extensive use of distributed circuits at higher frequencies. -
AN826 Crystal Oscillator Basics and Crystal Selection for Rfpic™ And
AN826 Crystal Oscillator Basics and Crystal Selection for rfPICTM and PICmicro® Devices • What temperature stability is needed? Author: Steven Bible Microchip Technology Inc. • What temperature range will be required? • Which enclosure (holder) do you desire? INTRODUCTION • What load capacitance (CL) do you require? • What shunt capacitance (C ) do you require? Oscillators are an important component of radio fre- 0 quency (RF) and digital devices. Today, product design • Is pullability required? engineers often do not find themselves designing oscil- • What motional capacitance (C1) do you require? lators because the oscillator circuitry is provided on the • What Equivalent Series Resistance (ESR) is device. However, the circuitry is not complete. Selec- required? tion of the crystal and external capacitors have been • What drive level is required? left to the product design engineer. If the incorrect crys- To the uninitiated, these are overwhelming questions. tal and external capacitors are selected, it can lead to a What effect do these specifications have on the opera- product that does not operate properly, fails prema- tion of the oscillator? What do they mean? It becomes turely, or will not operate over the intended temperature apparent to the product design engineer that the only range. For product success it is important that the way to answer these questions is to understand how an designer understand how an oscillator operates in oscillator works. order to select the correct crystal. This Application Note will not make you into an oscilla- Selection of a crystal appears deceivingly simple. Take tor designer. It will only explain the operation of an for example the case of a microcontroller. -
AN-400 a Study of the Crystal Oscillator for CMOS-COPS
AN-400 A Study Of The Crystal Oscillator For CMOS-COPS Literature Number: SNOA676 A Study of the Crystal Oscillator for CMOS-COPS AN-400 National Semiconductor A Study of the Crystal Application Note 400 Oscillator for Abdul Aleaf August 1986 CMOS-COPSTM INTRODUCTION TABLE I The most important characteristic of CMOS-COPS is its low A. Crystal oscillator vs. external squarewave COP410C power consumption. This low power feature does not exist change in current consumption as a function of frequen- in TTL and NMOS systems which require the selection of cy and voltage, chip held in reset, CKI is d4. low power IC's and external components to reduce power I e total power supply current drain (at VCC). consumption. Crystal The optimization of external components helps decrease the power consumption of CMOS-COPS based systems Inst. cyc. V f ImA even more. CC ckI time A major contributor to power consumption is the crystal os- 2.4V 32 kHz 125 ms 8.5 cillator circuitry. m Table I presents experimentally observed data which com- 5.0V 32 kHz 125 s83 pares the current drain of a crystal oscillator vs. an external 2.4V 1 MHz 4 ms 199 squarewave clock source. 5.0V 1 MHz 4 ms 360 The main purpose of this application note is to provide ex- perimentally observed phenomena and discuss the selec- External Squarewave tion of suitable oscillator circuits that cover the frequency Inst. cyc. range of the CMOS-COPS. V f I CC ckI time Table I clearly shows that an unoptimized crystal oscillator draws more current than an external squarewave clock. -
Unit I - Feedback Amplifiers Part - a 1
EC6401 Electronic Circuits II Department of ECE 2014-2015 UNIT I - FEEDBACK AMPLIFIERS PART - A 1. Define positive and negative feedback? Ans: Positive feedback: If the feedback voltage (or current) is so applied as to increase the input voltage (i.e. it is in phase with it), then it is called positive feedback. Negative feedback: If the feedback voltage (or current) is so applied as to reduce the input voltage (i.e. it is 180out of phase with it), then it is called negative feedback. 2. What are the advantages of negative feedback? Ans: The advantages of negative feedback are higher fidelity and stabilized gain, increased bandwidth, less distortion and reduced noise and input & output impedances can be modified as desired. 3. List four basic types of feedback? Ans: (1) Voltage series feedback (2) Voltage shunt feedback (3) Current series feedback and (4) Current shunt feedback. 4. Negative feedback is preferred to other methods of modifying Amplifier characteristics. Why? Ans: Negative feedback is preferred to other methods of modifying Amplifier Characteristics because it has the following advantages of reduction in distortion, stability in gain, increased bandwidth etc. 5. State the condition in (1+A) which a feedback amplifier must satisfy in order to be stable. Ans: The two important and necessary conditions are (1) The feedback must be positive, (2) Feedback factor must be unity i.e. A = 1 6. What is meant by phase and gain margin? Ans: Phase Margin: It is defined as 1800 minus the magnitude of the Aat the frequency at which A is unity. If he phase margin is negative the system is stable otherwise unstable. -
Simple Blocking Oscillator Performance Analysis for Battery Voltage Enhancement
Journal of Mobile Multimedia, Vol. 11, No.3&4 (2015) 321-329 © Rinton Press SIMPLE BLOCKING OSCILLATOR PERFORMANCE ANALYSIS FOR BATTERY VOLTAGE ENHANCEMENT DEWANTO HARJUNOWIBOWO ESMART, Physics Education Department, Sebelas Maret University, Indonesia [email protected] RESTU WIDHI HASTUTI Physics Education Department, Sebelas Maret University, Indonesia [email protected] KENNY ANINDIA RATOPO Physics Education Department, Sebelas Maret University, Indonesia [email protected] ANIF JAMALUDDIN ESMART, Physics Education Department, Sebelas Maret University, Indonesia [email protected] SYUBHAN ANNUR FKIP MIPA, Lambung Mangkurat University, Indonesia An application Blocking Oscillator (BO) on a battery to power a system LED lamp light detector has been built and compared with a standard system used phone cellular adapter as the power supply. The performance analysis was carried out to determine the efficiency of the blocking oscillator and its potency to be adopted in an electronic appliance using low voltage and current from a battery. Measurements were taken using an oscilloscope, a multimeter, and a light meter. The results show that the system generates electrical pulses of 1.5 to 7.6 VDC and powering the system normally. The system generates 3.167 mW powers to produce the intensity of 176 Lux. On the contrary, the standard system needs 1.8mW to produce 5 Lux. A LED usually takes at least 60mW to get 7150 Lux. Therefore, the system used a simple blocking oscillator seems potential to provide high voltage for powering electronic appliances with low current. Key words: blocking oscillator, characteristic, efficiency, LED, pulse 1 Introduction A design of circuit based on blocking oscillator for light up a LED using waste battery was carried out. -
Oscillator Circuits
Oscillator Circuits 1 II. Oscillator Operation For self-sustaining oscillations: • the feedback signal must positive • the overall gain must be equal to one (unity gain) 2 If the feedback signal is not positive or the gain is less than one, then the oscillations will dampen out. If the overall gain is greater than one, then the oscillator will eventually saturate. 3 Types of Oscillator Circuits A. Phase-Shift Oscillator B. Wien Bridge Oscillator C. Tuned Oscillator Circuits D. Crystal Oscillators E. Unijunction Oscillator 4 A. Phase-Shift Oscillator 1 Frequency of the oscillator: f0 = (the frequency where the phase shift is 180º) 2πRC 6 Feedback gain β = 1/[1 – 5α2 –j (6α – α3) ] where α = 1/(2πfRC) Feedback gain at the frequency of the oscillator β = 1 / 29 The amplifier must supply enough gain to compensate for losses. The overall gain must be unity. Thus the gain of the amplifier stage must be greater than 1/β, i.e. A > 29 The RC networks provide the necessary phase shift for a positive feedback. They also determine the frequency of oscillation. 5 Example of a Phase-Shift Oscillator FET Phase-Shift Oscillator 6 Example 1 7 BJT Phase-Shift Oscillator R′ = R − hie RC R h fe > 23 + 29 + 4 R RC 8 Phase-shift oscillator using op-amp 9 B. Wien Bridge Oscillator Vi Vd −Vb Z2 R4 1 1 β = = = − = − R3 R1 C2 V V Z + Z R + R Z R β = 0 ⇒ = + o a 1 2 3 4 1 + 1 3 + 1 R4 R2 C1 Z2 R4 Z2 Z1 , i.e., should have zero phase at the oscillation frequency When R1 = R2 = R and C1 = C2 = C then Z + Z Z 1 2 2 1 R 1 f = , and 3 ≥ 2 So frequency of oscillation is f = 0 0 2πRC R4 2π ()R1C1R2C2 10 Example 2 Calculate the resonant frequency of the Wien bridge oscillator shown above 1 1 f0 = = = 3120.7 Hz 2πRC 2 π(51×103 )(1×10−9 ) 11 C. -
Ultra Low Power RC Oscillator for System Wake-Up Using Highly
Ultra Low Power RC Oscillator for System wake-up using highly precise Auto-Calibration Technique Joonhyung, Lim#1, Kwangmook, Lee#2, Koonsik, Cho#3 # Ubiquitous Conversion Team, Samsung Electro-Mechanics, Suwon, Gyunggi-Do, Korea, 443-743 [email protected], [email protected], [email protected] Abstract— An ultra low power RC oscillator for system wake-up A. The design of RC oscillator is implemented using 0.18um CMOS process. The modern mobile systems need system clock which consumes low power and thus saves limited battery power in order to wake up from sleep-mode. A RC oscillator operates in the subthreshold region to reduce current consumption. The output frequency of RC oscillator is very weakly dependent on process and temperature variation using auto-calibration. This RC oscillator is featured as follows: the current consumption is 0.2 ㎂; the supply voltage is 1.8V; the output frequency is 31.25 KHz with 1.52(Relative 3σ)% accuracy after calibration; it has only 0.4%/℃ temperature coefficient; its size is 190 um x 80 um exclude bonding pad. I. INTRODUCTION Many applications, such as PDA, mobile communication devices need to operate with low power consumption and low supply voltage to fulfil the requirement of long-term operation. For such System-on-Chips (SoCs), embedded a system wake up circuit is necessary [1]. Several analogue and digital blocks such as clock generator, timer and SRAM for retention must be activated to wake system up from a sleep-mode. Especially, a clock generator, which is the heart of digital circuits, will output unknown waveform of clock and the system will enter Fig.