DOCSLIB.ORG

Wien-Bridge Oscillator with Low Harmonic Distortion

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Wien-Bridge Oscillator with Low Harmonic Distortion WIRELESS WORLD MAY 1981 51 Wien-bridge oscillator with low harmonic distortion New way of using Wien network to give 0.001 % t.h.d. by J. L. Linsley Hood, Robins (Electronics) The Wien-bridge network can be 1kHz of some 0.003%, which tended to connected in a different way in an increase with frequency above this point, R oscillator circuit to give a sine wave as the effectiveness of the common-mode with very low total harmonic isolation deteriorated. distortion. An I.e.d/photocell However, it is not implicit, in the use of a Wien network as the frequency-control amplitude control is external to the Output circuit. method, that the configuration shown in Fig. 1, in which the output of the network is taken to the non-inverting input of the R The Wien-bridge network remains the amplifier and the amplitude controlling most popular method of construction of negative-feedback signal is taken to the variable-frequency sine-wave oscillators, other, is the only circuit configuration since the basic circuit can be very simple in which can be employed. In particular, con­ ov form. It is a fairly straightforward matter sideration of the phase and transmission to design oscillators of this type in which characteristics of such a network, shown in Table 1 and Fig. 2 for equal values of C the harmonic distortion is only of the order Fig. 1. Basic Wien-bridge oscillator circuit of 0.01-0.02%, and which allow frequency control by means of a simple 2-gang poten­ Fig. 2. Gain and phase characteristics of tiometer. Wien network 1-0 131 The basic circuit for an oscillator of this O· 9 form, using a single operational amplifier z 0 o 8 w_ as the gain block, is shown in Fig. 1, and >Vl _Vl 7 the author has shown a practical design of z O· �-IVli: 121 oscillator, based on this, for a use as a wz §lO· 6 0: Vl « " 0: simple, general-purpose workshop tool. 1 f- i:Vl O· ....... However, in the form shown in Fig. 1, a �O 4 ............ significant problem exists in that the trans­ 0: ..... 111 f- 3 mission of a normal Wien network, at the O. .......z�-- w ,/7 " '/}:;II)' Vl operating frequency, is only 113, which O·2 0 ;! / '-... � CL means that an inconveniently large propor­ O·1 I tion of the output signal voltage appears at 0 the inputs of the amplifier, and will lead to 01 02 04 0·6 0 2 4� OSCILLATION FREQUENCY non-linearities in the transfer characteris­ - 9Cf' tics of the amplifier due to 'common mode' defects. An oscillator design, which em­ ployed an input device operated in a cas­ Fig. 3. Rearrangement of Wien network code configuration with a junction f.e. t. to R between signal sources gives small in­ minimize this type of defect, was shown by phase signal at point X the author in 1977,6 and allowed a t.h.d. at -..... '---...... ov (al Ibl Fig. 4. Use of arrangement of Fig. 3 in TABLE 1. Phase and transmission charac­ oscillator circuit teristics of simple Wien network. FIFa phase transmission 0.1 73.14° 0.10 R 0.2 57.99° 0.18 0.3 45.32° 0.23 0.4 34.99° 0.27 0.5 26.57" 0.30 Outr>ut 0.6 19.57° 0.31 I-Eyl 0.7 13.65° 0.32 0.8 8.53° 0.33 R 0.9 4.03° 0.33 1.0 0° 0.33 1.2 -6.97" 0.33 1.5 -15.52° 0.32 2 -26.57" 0.30 ----4�-------�-------_OV 3 -41.63° 0.25 Figures in brackets 5 -57.99° 0.18 refer to diagram 3 b 8 -69.15° 0.12 10. -73.14° 0.10 52 WIRELESS WORLD MAY 1981 and R, implies that if, instead of the net­ be significantly lower, because of the very operating frequency of the oscillator. Fast work of Fig. 3(a) being connected between small input-signal amplitude and the ab­ response-speed, high h.f. gain op.-amps. a signal source Ein and the OV line, it was sence of any internal transfer errors be­ can therefore be used without problems. connected between two signal sources + E x tween the inverting and non-inverting in­ and -Ey, where these are sinusoidal and puts, than is the case for an identical For these reasons, it can be expected identical in frequency and the negative amplifying element in a series-feedback that the residual harmonic distortion of sign implies phase opposition, as shown in configuration.3,4 this oscillator design will be exceedingly Fig. 3(b), then a small, in-phase signal • The time-delay errors in the second am­ small, and measurements on two proto­ would exist at the point 'X', at the fre­ plifying stage (A2) no longer contribute to types have indeed shown this to be the quency of maximum transmission, (fo), if loss of stablility in the system, but only to a case. So far as can be determined, the +Ex was slightly greater than -2Ey• very small compensatory shift in the residual distortion - almost exclusively This could then be used as a positive­ feedback signal in a circuit such as that shown in Fig. 4, to sustain oscillation at R the frequency fo. Indeed, such a circuit will work quite well, and will sustain a Thermistor Rs constant output magnitude of oscillation if a thermistor is employed, as shown, to make the gain of the second, inverting, Output amplifier stage dependent on the ampli­ tude of the input signal. However, there is, in practice, a small snag with such an R arrangement, and that is that the inverted negative-feedback signal applied to the in­ put of Al will suffer an additional phase ____�� --------------��------------��OV error due to the internal time lag within Figures in brackets Rp. Rs and Rin chosen to SUIt individual thermistor A2, and this will cause unwanted h.f. insta­ refer to diagnom 3b employed bility if '3rd generation' high speed op.­ amps. such as the CA 3140, or the 174 1 S, Fig. 5. Final form of new configuration in low-distortion oscillator are used in the realisation of this circuit. It is, fortunately, an easy matter to re­ solve this difficulty if the circuit is recast in 0·01 the form shown in Fig. 5, in which the ·009 , (Includes negative-feedback signal, equivalent to ,50 Hz "hum" I ·005 " -Ey in Fig. 3(b), is derived from the am­ plifier AI> and the positive-feedback signal "- , is obtained from the output of the second "- � ..... inverting amplifier A2• :z o ..... .... This configuration offers several signifi­ 0001 .... �o ... cant advantages. l­ ... �--- V) • The input signal to Al is extremely a .0005 small, since it is only required to be EOUl/2M, where M is the open-loop gain of AI - typically 100dB for a good modern op.amp. i.c. - and, as pointed out by the 2 author in an earlier article , with semi­ 00001 100 lk conductor amplifiers the non-linearity of 1Ok FREQUENCY such devices is essentially an input charac­ (Hz) teristic, dependent on the magnitude of Fig. 6. Measured total harmonic distortion of improved oscillator of Fig. 5 the input signal. • The second-stage amplifier is operated as a shunt-feedback element, and the non­ Fig. 7. New oscillator with external optoelectronic amplitude-control circuit. Silonex linearities of such a stage can be shown to (formerly National Semiconductors) cell, Type NSL395, is obtainable from Cheston Electronics Ltd., Vanguard House, 56 Oughton Street, Ormskirk, Lancs. Tel: 069572456 1/ Photoconductive cell 10k NSL395 10}! 47k Si 3k3 56k Si Si I1 3k3 3k3 3k3 \�--------------�vr--------------�/ \�------------------�vr------------------�/ \�------,v�----�/ Feedback control Oscillator Full wave rectifier circuit Output Note: PC and LED are in optical contact 1 1 WIRELESS WORLD MAY 1981 53 third harmonic - is that due to the de­ photo-conductive cell and the light-emit­ Measuring tranSient pendence of the resistance of the thermis· ting diode combination shown in Fig. 7, in tors used to control the amplitude of the which the time constant and other dy­ intermodulation of oscillation on the instantaneous value namic characteristics of the control circuit continued from page 47 the signal potential applied to them. This can be optimized by a suitable combina­ limiting filter. characteristic of oscillators with averaging tion of proportional, integral and differen­ The authors are interested in measuring control s�stems has been analysed by tial (p.i.d.) adjustment to the gain of the t.i.m. principally to test the effectiveness Robinson who suggests that the distortion control circuit (A2). Needless to say, the of anti-t.i.m. measures such as input filt­ of such a system, which is shown to be photoresistive element should be chosen to ers, and to design low-t.i.m. monolithic mainly third harmonic, will be have a very low voltage coefficient of resis­ amplifiers. The availability of a simple and tance and an adequate response speed to X3 _ 1 . Ao-l'j 1 accurate measuring system has already -- avoid the introduction of a further signifi­ Xl l'j provided useful results, exemplified by the - 8rj . 'Iitji cant time delay into the control loop. R.I.A.A. preamplifier shown in Fig. 12; a where (Ao-l'j)/l'j is the fraction by which Leaving aside the question of the means circuit designed around the TDA32 10 ste­ the low-level loop gain exceeds the gain employed to control the amplitude of the reo preamplifier i.c.
Load more

Recommended publications
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • Van Der Pol Approximation Applied to Wien Oscillators João Casaleiroa,B,∗, Luís B
    Available online at www.sciencedirect.com ScienceDirect Procedia Technology 17 ( 2014 ) 335 – 342 Conference on Electronics, Telecommunications and Computers – CETC 2013 Van der Pol Approximation Applied to Wien Oscillators João Casaleiroa,b,∗, Luís B. Oliveirab, António C. Pintoa aDep. of Electronics, Telecommunications and Computers Engineering, Instituto Superior de Engenharia de Lisboa - ISEL, Lisboa, Portugal bDepartment of Electrical Engineering, FCT, CTS-Uninova, Caparica, Portugal Abstract This paper presents a nonlinear analysis of the Wien type oscillators based on the Van der Pol approximation. The steady-state equations for the key parameters, frequency and amplitude, are derived and their sensitivities to ambient temperature are discussed. The added value of this work is to present an analytical method to obtain the fundamental characteristics of the Wien type oscillators and to relate these characteristics with the circuit parameters in a simpler manner. The simulation results confirm the amplitude and frequency equations, and confirm that the amplitude is controlled by the limiter circuit. ©c 20142014 TheThe Authors. Authors. Published Published byby Elsevier Elsevier Ltd. Ltd. This is an open access article under the CC BY-NC-ND license (Selectionhttp://creativecommons.org/licenses/by-nc-nd/3.0/ and peer-review under responsibility of ISEL). – Instituto Superior de Engenharia de Lisboa. Peer-review under responsibility of ISEL – Instituto Superior de Engenharia de Lisboa, Lisbon, PORTUGAL. Keywords: Oscillator, Wien oscillator, quasi-sinusoidal, Van der Pol, amplitude stabilization. 1. Introduction The oscillators of the Wien type are well known, second order, quasi-sinusoidal oscillators, suited for low frequencies and low distortion applications [1]. The low-distortion feature of this type of oscillator justifies its use for the characterization of analog-to-digital converters (ADC)[2], instrumentation circuits and a wide variety of measurement circuits.
    [Show full text]
  • PH-218 Lec-16: Oscillator
    Analog & Digital Electronics Course No: PH-218 Lec-16: Oscillator Course Instructors: Dr. A. P. VAJPEYI Department of Physics, Indian Institute of Technology Guwahati, India 1 Positive Feedback When input and feedback signal both are in same phase, It is called a positive feedback. Positive feedback is used in analog and digital systems. A primary use of +ve feedback is in the production of oscillators. + Vi Vs Σ A( f) Vo + Vf SelectiveNetwork β(f) V A o = V = AV = A(V +V ) and V f = βVo o i s f Vs 1− Aβ Barkhausen Criterion: for oscillator βA=1 and +ve feedback 2 Oscillator Circuit Oscillator is an electronic circuit which converts dc signal into ac signal. Oscillator is basically a positive feedback amplifier with unity loop gain. For an inverting amplifier- feedback network provides a phase shift of 180 °°° while for non-inverting amplifier- feedback network provides a phase shift of 0°°° to get positive feedback . Vo A = If βA=1 then V o = ∞ ; Very high output with zero input. Vs 1− Aβ Use positive feedback through frequency-selective feedback network to ensure sustained oscillation at ω0 Use of Oscillator Circuits Clock input for CPU, DSP chips … Local oscillator for radio receivers, mobile receivers, etc As a signal generators in the lab Clock input for analog-digital and digital-analog converters 3 Oscillators If the feedback signal is not positive and gain is less than unity, oscillations dampen out. If the gain is higher than unity then oscillation saturates. Type of Oscillators Oscillators can be categorized according to the types of feedback network used: RC Oscillators: Phase shift and Wien Bridge Oscillators LC Oscillators: Colpitt and Hartley Oscillators Crystal Oscillators 4 RC Oscillators R −1 X C Vo = ( )Vin and φ = tan ( ) R − jX c R o o Φ =0 if Xc=0 and Φ =90 if R=0 However adjusting R to zero is impractical because it would lead to no voltage across R, thus in a RC circuit, phase shift is always ≤ 90 o and it is a function of frequency.
    [Show full text]
  • The Barkhausen Criterion (Observation ?)
    View metadata,Downloaded citation and from similar orbit.dtu.dk papers on:at core.ac.uk Dec 17, 2017 brought to you by CORE provided by Online Research Database In Technology The Barkhausen Criterion (Observation ?) Lindberg, Erik Published in: Proceedings of NDES 2010 Publication date: 2010 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Lindberg, E. (2010). The Barkhausen Criterion (Observation ?). In Proceedings of NDES 2010 (pp. 15-18). Dresden, Germany. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. 18th IEEE Workshop on Nonlinear Dynamics of Electronic Systems (NDES2010) The Barkhausen Criterion (Observation ?) Erik Lindberg, IEEE Life member Faculty of Electrical Eng. & Electronics, 348 Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark Email: [email protected] Abstract—A discussion of the Barkhausen Criterion which is a necessary but NOT sufficient criterion for steady state oscillations of an electronic circuit.
    [Show full text]
  • Wien Bridge Oscillator
    Wien Bridge Oscillator Conventional analysis Consider the amplifier shown below. The potential at the noninverting input is equal to the input signal: v+ = vi . The potential at the invertiing input is related to the output via a voltage-divider: Rf1 v− = vo . Rf1 + Rf2 Using the ideal op-amp assumption that v+ = v– leads to vo = Gvi where Rf2 G ≡ 1 + . Rf1 This is the standard non-inverting amplifier configuration. Now let's ask if we can sustain a finite output if, instead of an external input, we feed the output back to the input through a frequency-dependent network. Using complex phasor notation such that v = ℝVê jωt (where ℝ means "real part of") , we write Vî = H(ω)Vô . We also had Vô = G(ω)Vi.̂ (Note: in the current case G actually does not have any frequency dependence. The notation is for purposes of generality.) Self-consistency requires Vî = G(ω)H(ω)Vi.̂ This requires that the loop gain G(ω)H(ω) = 1. This is the Barkhausen condition for oscillation, which implies both that the magnitude of the loop gain is unity and that the phase shift is zero or a multiple of 2π . Wien Bridge Consider the resistance - capacitance network shown above. Z1 i = o. Z1 Vî = Vô . Z1 + Z2 R 1+jωRC Vî = Vô . R R j 1 1+jωRC + ( − ωC ) 1 Vî = Vô . j ωRC 1 3 + ( − ωRC ) Thus 1 H(ω) = . j ωRC 1 3 + ( − ωRC ) Remember that Vô = GVî with G having the real value Rf2 G = 1 + Rf1 .
    [Show full text]
  • CHAPTER Feedback Amplifier & Oscillators
    Analog Circuits Day-12 Oscillators Introduction to Feedback: The phenomenon of feeding a portion of the output signal back to the input circuit is known as feedback. The effect results in a dependence between the output and the input and an effective control can be obtained in the working of the circuit. Feedback is of two types. • Negative Feedback • Positive Feedback Negative or Degenerate feedback: • In negative feedback, the feedback energy (voltage or current), is out of phase with the input signal and thus opposes it. • Negative feedback reduces gain of the amplifier. It also reduce distortion, noise and instability. • This feedback increases bandwidth and improves input and output impedances. • Due to these advantages, the negative feedback is frequently used in amplifiers. NegativeFeedback Positive or regenerate feedback: • In positive feedback, the feedback energy (voltage or currents), is in phase with the input signal and thus aids it. Positive feedback increases gain of the amplifier also increases distortion, noise and instability. • Because of these disadvantages, positive feedback is seldom employed in amplifiers. But the positive feedback is used in oscillators. Positive Feedback In the above figure, the gain of the amplifier is represented as A. The gain of the amplifier is the ratio of output voltage Vo to the input voltage Vi. The feedback network extracts a voltage Vf = β Vo from the output Vo of the amplifier. This voltage is subtracted for negative feedback, from the signal voltage Vs. Now, Vi=Vs + Vf =Vs+βVo The quantity β = Vf/Vo is called as feedback ratio or feedback fraction. The output Vo must be equal to the input voltage (Vs + βVo) multiplied by the gain A of the amplifier.
    [Show full text]
  • Operational Amplifiers Is That the User Often Finds That They Oscillate in Connections He Wishes Were Stable
    CHAPTER XII ADVANCED APPLICATIONS 12.1 SINUSOIDAL OSCILLATORS One of the major hazards involved in the application of operational amplifiers is that the user often finds that they oscillate in connections he wishes were stable. An objective of this book is to provide guidance to help circumvent this common pitfall. There are, however, many applications that require a periodic waveform with a controlled frequency, waveshape, and amplitude, and operational amplifiers are frequently used to generate these signals. If a sinusoidal output is required, the conditions that must be satisfied to generate this waveform can be determined from the linear feedback theory presented in earlier chapters. 12.1.1 The Wien-Bridge Oscillator The Wien-bridge corifiguration (Fig. 12.1) is one way to implement a sinusoidal oscillator. The transfer function of the network that connects the output of the amplifier to its noninverting input is (in the absence of loading) V.(s) _ RCs 2 V0(s) ~ R Cess + 3RCs + 1 The operational amplifier is connected for a noninverting gain of 3. Com­ bining this gain with Eqn. 12.1 yields for a loop transmission in this positive-feedback system 3RCs L(s) = C2s 2 3RCs (12.2) R2Cs + 3RCs + 1 The characteristic equation 3RCs R2C2 s2 + 1 I - L(s) = 1 - 3RsR222+1 (12.3) R2C2 s 2 + 3RCs + 1 R2 C2s 2 + 3RCs + 1 has imaginary zeros at s = ±(j/RC), and thus the system can sustain constant-amplitude sinusoidal oscillations at a frequency w = 1/RC. 485 486 Advanced Applications 2R, R R C +0 Va C R Figure 12.1 Wien-bridge oscillator.
    [Show full text]
  • Wien Bridge Oscillator
    Wien Bridge Oscillator Introduction Oscillators are circuits that produce periodic waveforms without any input signal. They generally use some form of active devices like transistors or OPAMPs as amplifiers with feedback network consisting of passive devices such as resistors, capacitors, or inductors. Fig.1 demonstrates the a basic negative feedback system in which VIN is the input voltage, VOUT is the output voltage from the amplifier gain block (A), and β as the feedback factor, that is fed back to the summing junction. E represents the error signal that is equal to the summation of the feedback factor and the input voltage. Figure 1 Basic block diagram explaining feedback When Aβ = 1, i.e. the unity loop gain with phase shift of 180° provided by the feedback network (Aβ= 1∠–180°), the denominator term becomes 0 and the gain with feedback, , becomes infinite. This means infinitesimal signal (noise voltage) can provide an output voltage, and the circuit acts as an oscillator even without an input signal. This is Barkhausen Criterion for sustained oscillations. This can be explained using control theory using following three conditions: 1. If the loop gain Aβ <1, the poles of the transfer function Af, lie in the left half of the s-Plane (real part σ being negative). The system oscillates but eventually they die out. (Refer Fig 2a) 2. If the loop gain Aβ=1, the poles of the transfer function (which are complex conjugates with real part σ equal to zero) of the closed loop system lie on the jω axis. However, in reality, the nonlinearity of the circuit components eventually causes Aβ to become less than one and the oscillations cease out.
    [Show full text]
  • INSTITUTION Controlledoscillators. Each Lesson Follows a Typical
    DOCUMENT RESUME ED 190 906 CE 026 591 TITLE ' Military Curricula'for Vocational & Technical . Education. Baied Electricity and Electronics*. CANTRAC A-100%0010. Module 32: Intermediate Oscillators. Study Booklet. INSTITUTION Chief of Naial Education and Training Support, Pensacola, Fla.: Ohio State Univ., Columbus. National Center for Research in Vocational Education. '. FEPORT No CMTT-E-050 rut DATE Jul BO NOTE 262p.:Forfrelateddocuments see CE 026 560-593. --, , EDRS PRICE MFO1 /PC11 Plus Postage. DESCFIFTORS . *Electricty: *Electronics: Individualized Instruction: Learning Activities: Learning Modules: Postsecondary Education: Programed Instruction:' *Technical Education IDENTIFIERS Military COrriculum Project: *Oscillators ABSTRACT This individualized learning module on intermediate oscillators is one in a series of modules for a course in basic electricity and electronics. The course is one of a number of military-developed curriculum packages selected for adaptation to vocational instructional and curriculum develbpsent in a civilian setting. Five lessons are included in the module: (1) Hartley . Oscillators,(2) Resistiye Capacitive Phase Shift Oscillators, (21 Wien.-Bridge Cscillators, (U) Blocking Oscillators, and(5) Crystal ControlledOscillators. Each lesson follows a typical format including a lesson overview, a list of study resources, the lesson content, a programmed instruction sections, and .a lesson summary. (Progress checks and other supplementary material are provided for each lesson in a students guide, CE 026 590.1 (LEA) i' *********************************************************************** * Reproductions supplied by EDRS are the best that can be jade * * from the original document. * *********************************************************************** rd. .1770.1114.131Pr Ara:AIL* %IR 6 10 411. t v-- . C:k LAJ CHIEF OF NAVAL EDUCATION AND TRAINING.1, ilitaryurrla CNTT-E-054. \\.. 4- al JULY 1980 we' Technical Education I BASIC ELECTRICITY AND ELECTRONICS'.
    [Show full text]
  • Wien Bridge Oscillator Using Op-Amp for a Given Frequency of 1Khz
    Experiment No. 9 WIEN BRIDGE OSCILLATOR USING OPAMP AIM: To design a Wien Bridge oscillator using op-amp for a given frequency of 1kHz. THEORY: An oscillator is a circuit that produces periodic electric signals such as sine wave or square wave. The application of oscillator includes sine wave generator, local oscillator for synchronous receivers etc. An oscillator consists of an amplifier and a feedback network. 1. 'Active device' i.e. opamp is used as an amplifier. 2. Passive components such as R-C or L-C combinations are used as feedback network. To start the oscillation with the constant amplitude, positive feedback is not the only sufficient condition. Oscillator circuit must satisfy the following two conditions known as Barkhausen conditions: 1. Magnitude of the loop gain (Av β) = 1, where, Av = Amplifier gain and β = Feedback gain. Fig 1. Basic oscillator block diagram 2. Phase shift around the loop must be 360° or 0°. Wien bridge oscillator is an audio frequency sine wave oscillator of high stability and simplicity. The feedback signal in this circuit is connected to the non-inverting input terminal so that the op-amp is working as a non-inverting amplifier. Therefore, the feedback network need not provide any phase shift. The circuit can be viewed as a Wien bridge with a series combination of R1 and C1 in one arm and parallel combination of R2 and C2 in the adjoining arm. Resistors R3 and R4 are connected in the remaining two arms. The condition of zero phase shift around the circuit is achieved by balancing the bridge.
    [Show full text]
  • Early Vintage Hewlett-Packard Oscillators 1938-1941 by Kenneth A
    Early Vintage Hewlett-Packard Oscillators 1938-1941 by Kenneth A. Kuhn August 4, 2008, rev. 6, Aug. 22, 2009 This is an article in progress. Revisions will be made as more information is discovered. Introduction Many people who have acquired or found a vintage HP oscillator have inquired to the author as to whether that oscillator could have been built in the famous garage. The answer is always no. Only a very small number of oscillators were built in the garage and typical oscillators people own have characteristics that prove that they were constructed years after the garage days. However, a recent inquiry had enough credible characteristics to inspire the author to explore deeper into the history of the oscillators and write this article. It turns out that it is almost a certainty that that oscillator was built in the garage and the author is very glad to have been able to analyze detailed pictures of it. A picture of the front of that oscillator is shown in Figure 1. It probably has been repainted at some point as the normal color was gray like shown in Figure 4 and the red fill in the engraving was probably added by some owner over the years as every example of engraved panels the author is aware of are unfilled. The original metal output binding posts have been replaced by more modern plastic versions. The author is aware of at least four of the small case units in existence. Figure 1: A recently discovered garage vintage oscillator (photo courtesy of Cal Taylor) The purpose of this article is to provide all of the known information (which is not very much) concerning the earliest vintage oscillators built by the Hewlett-Packard Company.
    [Show full text]