Section 2. Oscillator
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Crystal Oscillators 1
Crystal oscillators 1. Objectives The aim of the exercise is to get acquainted with issues concerning the generation of waveforms (including sinewaves) in the basic structures of crystal generators. In addition, the exercise aims to familiarize with surface mount technique SMT (Surface Mount Technology/ Technics or SMD – Surface mounting Devices). 2. Components and instrumentation. In the exercise, it is possible to test quartz generators operating in the three simplest and most popular system structures: • Colpitts-Pierce quartz generator with bipolar transistor, • quartz generator implemented on TTL gates, • quartz generator implemented on CMOS inverters 2.1. Colpittsa-Pierce’s oscillator with bipolar transistor. The Colpitts-Pierce quartz generator system working in parallel resonance is shown in Fig. 1. + UCC Rb C2 XT C1 Re UWY Fig. 1. Colpittsa-Pierce oscillator with BJT. Using, in the system, quartz resonators with resonance values up to several tens of MHz, the elements C1, Re in the generator system can be selected according to the graph shown in Fig.2. RezystorRe [Ohm] Frequency [MHz] Fig. 2. Selection of C1 and Re elements in the Colpitts-Pierce oscillator 2.2. Quartz oscillator implemented using TTL digital IC Fig. 3 presents a diagram of a quartz oscillator implemented using NAND gates in TTL technology. The oscillator works in series resonance. In this system, while maintaining the same resistance values, quartz resonators with a frequency from a few to 10 MHz can be used. 560 1k8 220 220 UWY XT Fig. 3. Cristal oscillator with serial resonance implemented with NAND gates in TTL technology In the laboratory exercise, it is proposed to implement the system using TTL series 74LS00 (pins of the IC are shown in in Fig.4). -
Analysis of BJT Colpitts Oscillators - Empirical and Mathematical Methods for Predicting Behavior Nicholas Jon Stave Marquette University
Marquette University e-Publications@Marquette Master's Theses (2009 -) Dissertations, Theses, and Professional Projects Analysis of BJT Colpitts Oscillators - Empirical and Mathematical Methods for Predicting Behavior Nicholas Jon Stave Marquette University Recommended Citation Stave, Nicholas Jon, "Analysis of BJT Colpitts sO cillators - Empirical and Mathematical Methods for Predicting Behavior" (2019). Master's Theses (2009 -). 554. https://epublications.marquette.edu/theses_open/554 ANALYSIS OF BJT COLPITTS OSCILLATORS – EMPIRICAL AND MATHEMATICAL METHODS FOR PREDICTING BEHAVIOR by Nicholas J. Stave, B.Sc. A Thesis submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Master of Science Milwaukee, Wisconsin August 2019 ABSTRACT ANALYSIS OF BJT COLPITTS OSCILLATORS – EMPIRICAL AND MATHEMATICAL METHODS FOR PREDICTING BEHAVIOR Nicholas J. Stave, B.Sc. Marquette University, 2019 Oscillator circuits perform two fundamental roles in wireless communication – the local oscillator for frequency shifting and the voltage-controlled oscillator for modulation and detection. The Colpitts oscillator is a common topology used for these applications. Because the oscillator must function as a component of a larger system, the ability to predict and control its output characteristics is necessary. Textbooks treating the circuit often omit analysis of output voltage amplitude and output resistance and the literature on the topic often focuses on gigahertz-frequency chip-based applications. Without extensive component and parasitics information, it is often difficult to make simulation software predictions agree with experimental oscillator results. The oscillator studied in this thesis is the bipolar junction Colpitts oscillator in the common-base configuration and the analysis is primarily experimental. The characteristics considered are output voltage amplitude, output resistance, and sinusoidal purity of the waveform. -
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 -
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. -
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. -
Crystals Load Capacitance Calculation And
Load Capacitance PRINTED: 12/21/2012 TYPICAL OSCILLATOR CIRCUIT OSC CELL OSC CELL = oscillator circuit integrated into any IC. Rf = feedback resistor, sometimes integrated in IC or is required as external resistor Rf CLOCK SIGNAL Cg = capacitance of oscillator input for IC internal use Cd = capacitance of oscillator output Rd = Phase shift resistor, necessary at lower frequencies to meet oscillation condition that phase shift all the way around the oscillator loop need to add up to 360°. Y1 = Quartz crystal unit C1 and C1 = external load capacitors. CPCB1 and CPCB2 = stray capacitances of PCB traces Cg Cd The total LOAD CAPACITANCE of the oscillator circuit is the sum of all capacitances. OSC IN OSC OUT consisting of: 1. The two external capacitors (here called C1 and C2) 2. The IC input and output capacitances (here called Cg and Cd) 3. The stray capacitances of PCB traces (here called CPCB1 and CPCB2) CPCB1 Rd Commonly being only the values of the external capacitors known so that a correct calculation of the actual load capacitance is not possible. SIGNAL OUTPUT OPTIONALCLOCK In such case we use simlified formula to calculate the load capacitance as: C1 C2 CL C TOTAL C1 C2 STRAY CPCB2 Here C1 and C2 are the external capacitors in the cricuit, values should be known. Cstray is summarized value for IC input and output capacitance and the PCB traces. Y1 Cstray in a 3.3VDC circuit is often 3~4pF. C1 C2 Cstray in a 5.0VDC circuit often 5~7pF. However, we have also seen circuits that had large deviation from these values. -
MEMS) Technology
Microchip Oscillators and Clocks Using Microelectromechanical Systems (MEMS) Technology Author: John Clark and Graham Mostyn The next milestone will be next-generation MEMS res- Microchip Technology Inc. onators that achieve very low phase noise for high-end communication systems. Microchip acquired MEMS timing technology through OVERVIEW the purchases of Discera and Micrel in 2015. Since Dis- For decades, oscillators and clocks have relied on cera shipped its first production oscillators in 2008, quartz crystals for the creation of a stable frequency almost 100 million devices have been manufactured reference. Crystals perform very well for many applica- and sold. tions. However, microelectromechanical systems This paper describes the benefits of a MEMS-based (MEMS) technology, replacing quartz crystals with solution, the resonator technology, and the design of MEMS resonators, entered the marketplace ten years the final product. ago and is rapidly maturing. MEMS-based timing devices offer high reliability KEY FUNCTIONALITY (including AEC-Q100 certification for automotive use), extended operating temperatures, small size, and low Microchip’s MEMS-based oscillators and clocks offer power consumption. Video surveillance, automotive benefits over traditional quartz solutions (Figure 1). ADAS, general industrial applications, and data trans- These include stable frequency, small size, high reli- mission to 10 Gbps are prime areas of usage today. ability, flexibility, many programmable features, fast guaranteed start-up, and high integration. FIGURE 1: Benefits of Microchip MEMS-Based Oscillators and Clocks. 2017 Microchip Technology Inc. DS00002344A-page 1 MICROCHIP RESONATOR quency of the beam and minimize vibrational energy TECHNOLOGY loss to the substrate. This, in turn, maximizes its quality factor and frequency selectivity. -
Microcontroller Oscillator Circuit Design Considerations by Cathy Cox and Clay Merritt
Freescale Semiconduct or, Inc... 2 CrystalOscillatorTheory 1 Introduction By CathyCoxandClayMerritt Considerations Microcontroller OscillatorCircuitDesign can beexpected,asignificantamountofpowerisrequiredtokeepanamplifierinlinearmode. digital NANDgateasananalogamplifierisnotlogical,butthishowoscillatorcircuitfunctions.As The voltageincreasesuntiltheNANDgateamplifiersaturates.Atfirstglance,thoughtofusinga energized, theloopgainmustbegreaterthanonewhilevoltageatXTALgrowsovermultiplecycles. overall loopgainequaltooneandanphaseshiftthatisintegermultipleof360 stabilize thefrequencyandsupply180 sists oftwoparts:aninvertingamplifierthatsuppliesavoltagegainand180 The Pierce-typeoscillatorcircuitshownin pitfalls. document istodevelopasystematicapproachgoodoscillatordesignandpointoutsomecommon ing crystalandmicrocontrollerfunctionswithoutthehelpofmatingspecifications.Theobjectivethis timing overawidetemperaturerangeusecrystaloscillator.PCBdesignershavethetaskofintegrat- The heartbeatofeverymicrocontrollerdesignistheoscillatorcircuit.Mostdesignsthatdemandprecise cy selectivefeedbackpath.ThecrystalcombinedwithC 1. 2.The M68HC11oscillatorcircuitpinsarelabeledXTALand EXTAL. forpowerconservation. STOP isaninternallygeneratedsignalthatdisablestheoscillator circuit EXTAL Cx STOP Figure 1PierceOscillator 2 ° phaseshiftfeedbackpath.Insteadystate,thiscircuithasan 1 Figure 1 Rf Y1 isusedonmostmicrocontrollers.Thiscircuitcon- x andC y formatunedPInetworkthattendsto XTAL Cy 2 ° phaseshiftandafrequen- Order thisdocument byAN1706/D ° . Uponbeing Freescale Semiconductor, -
CIRCUIT IDEAS for DESIGNERS Ultra Low Voltage Crystal Oscillator
Category: FET CIRCUIT IDEAS FOR DESIGNERS Schematic no. fet_11121.0 Ultra Low Voltage Crystal Oscillator Circuit using Active Loads Description This is an ultra low-voltage crystal oscillator circuit using EPAD MOSFETs with active load and output buffer. This circuit is similar to a standard crystal oscillator circuit used in 5V circuits. However, at low operating voltages, the values of the resistors and the impedance of the inverter MOSFET are selected to optimize oscillation stability and minimize power consumption. An active load device using a depletion mode EPAD MOSFET such as an ALD114804 replaces a passive resistor load at the inverter. Using appropriate component values, a crystal oscillator circuit can be configured to operate in the range of supply voltages from V+ = 5V to V+ = 0.5V, with crystal frequencies ranging from 1 MHz to 16 MHz. The active load reduces the contrast in the corresponding power consumption at different supply voltages. At V+= 5V the power consumed by the oscillator circuit is 346 µW whereas at V+= 0.5V, the same circuit consumes a mere 32 µW while oscillating at the same selected crystal frequency. At higher crystal frequencies in excess of 4 MHz, a dual EPAD MOSFET can be connected in parallel to provide more low voltage drive current necessary. Recommended Components EPAD MOSFETs: M1, M3 ALD110800 (either single or dual MOSFET connected in parallel); Active Load: M2 ½ ALD114904 CL1=10pF; CL2 = 22pF; RF= 5.6MOhm; RL= 6 Ohm; ROUT = 2.4KOhm Other Related Circuit Ideas Schematic no. fet_11120.0 Ultra Low Voltage Micropower Crystal Oscillator Circuit 2005 Advanced Linear Devices, Inc. -
EURO QUARTZ TECHNICAL NOTES Crystal Theory Page 1 of 8
EURO QUARTZ TECHNICAL NOTES Crystal Theory Page 1 of 8 Introduction The Crystal Equivalent Circuit If you are an engineer mainly working with digital devices these notes In the crystal equivalent circuit above, L1, C1 and R1 are the crystal should reacquaint you with a little analogue theory. The treatment is motional parameters and C0 is the capacitance between the crystal non-mathematical, concentrating on practical aspects of circuit design. electrodes, together with capacitances due to its mounting and lead- out arrangement. The current flowing into a load at B as a result of a Various oscillator designs are illustrated that with a little constant-voltage source of variable frequency applied at A is plotted experimentation may be easily modified to suit your requirements. If below. you prefer a more ‘in-depth’ treatment of the subject, the appendix contains formulae and a list of further reading. At low frequencies, the impedance of the motional arm of the crystal is extremely high and current rises with increasing frequency due solely to Series or Parallel? the decreasing reactance of C0. A frequency fr is reached where L1 is resonant with C1, and at which the current rises dramatically, being It can often be confusing as to whether a particular circuit arrangement limited only by RL and crystal motional resistance R1 in series. At only requires a parallel or series resonant crystal. To help clarify this point, it slightly higher frequencies the motional arm exhibits an increasing net is useful to consider both the crystal equivalent circuit and the method inductive reactance, which resonates with C0 at fa, causing the current by which crystal manufacturers calibrate crystal products. -
Single Transistor Crystal Oscillator Circuits
Copyright © 2009 Rakon Limited SINGLE TRANSISTOR CRYSTAL OSCILLATOR CIRCUITS The majority of modern crystal oscillator circuits fall into one of two design categories, the Colpitts / Clapp oscillator and the Pierce oscillator. There are other types of single transistor oscillators ( Hartley and Butler for example ), but their usefulness and application is beyond the scope of this discussion. For an electronic circuit to oscillate there are two criteria which must be satisfied. It must contain an amplifier with sufficient gain to overcome the losses of the feedback network (quartz crystal in this case) and the phase shift around the whole circuit is 0 o or some integer multiple of 360 o. To design a crystal oscillator the above has to be true but there are a myriad of other considerations including crystal power dissipation, unwanted mode suppression, crystal loading (the actual impedance the crystal sees once oscillation has started) and the introduction of a non-linearity in the gain to limit the oscillation build-up. Consider the apparently simple circuit of the Colpitts / Clapp oscillator in Fig. 1. Without the correct simulation tools it is not immediately obvious this circuit has Negative Resistance at the frequency of oscillation (necessary to over come the crystals Equivalent Series Resistance), an initial gain in excess of one (to allow oscillator start- up) which drops to unity once the oscillation starts, and is then subsequently stabilised by either the voltage limiting on the transistor’s base emitter junction, or transistor collector current starvation. For AT cut crystals this circuit, with careful choice of the component values, can be made to oscillate from about 1MHz to above 200MHz with complete control over the crystal drive level and crystal loading impedance. -
Simple Two-Transistor Single-Supply Resistor-Capacitor Chaotic Oscillator Lars Keuninckx, Guy Van Der Sande and Jan Danckaert†
IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II, VOL. X, NO. Y, DECEMBER 2015 1 Simple Two-Transistor Single-Supply Resistor-Capacitor Chaotic Oscillator Lars Keuninckx, Guy Van der Sande and Jan Danckaerty Abstract—We have modified an otherwise standard one- adding a dimension to a predominantly two-dimensional limit transistor self-biasing resistor-capacitor phase-shift oscillator to cycle oscillator. In other cases, notably the Collpits oscilla- induce chaotic oscillations. The circuit uses only two transistors, tor [7], a chaotic regime is already present for certain values no inductors, and is powered by a single supply voltage. As such it is an attractive and low-cost source of chaotic oscillations for of the design parameters. Others directly translate a known many applications. We compare experimental results to Spice chaotic system of differential equations to electronics. The simulations, showing good agreement. We qualitatively explain necessary nonlinear terms are implemented by using dedicated the chaotic dynamics to stem from hysteretic jumps between analog multipliers as in reference [8] or operational amplifier unstable equilibria around which growing oscillations exist. based piece wise continious functions [9]. Being able to Index Terms—chaos, oscillator. nonlinear dynamics, RC- avoid operational amplifiers and dedicated multipliers is a ladder. plus in terms of cost and circuit complexity, as there is Copyright (c) 2014 IEEE. Personal use of this material is no connection between complexity -in terms of used parts- permitted. However, permission to use this material for any of the circuit and complexity of the chaotic oscillations -in other purposes must be obtained from the IEEE by sending terms of measurable quantitative properties such as entropy, an email to [email protected] attractor dimension, spectral content etc.