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DYNAMICS OF AN OSCILLATOR FOR SINUSOIDAL INPUT

IRJET, 2022

An oscillator is the most basic element for generating sources of signals. It generates sinusoidal signals of required frequency and amplitude. It is the basic instrument used in electrical and electronic measurements in laboratories as well as researches. The applications include frequency modulation and amplitude modulation. Although we speak of an oscillator, as a generation of sinusoidal signal, it does not store any energy. The function of an oscillator is exactly reverse of that of a rectifier and therefore sometimes it is also called as inverter. Although an alternator also called as AC generator generates sinusoidal power of 50HZ but it cannot be called as an oscillator. This review paper gives a detailed idea of different types of oscillators present, their working principle, their frequency of oscillations, their gains with neat labelled diagrams.

Microwave/RF Oscillator Systems Stability Analysis

2017

An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. Oscillators are class of circuits with one terminal or port, which produce a periodic electrical output upon power up. Oscillators can be classified into two types: (a) Relaxation and (b) Harmonic oscillators. Relaxation oscillators (also called unstable multi-vibrator) is a class of circuits with two unstable states. The circuit switches back and forth between these states. The output is generally square waves. Harmonic oscillators are capable of producing near sinusoidal output, and are based on positive feedback approach.

Crystal Oscillators and Circuits

It is often required to produce a signal whose frequency or pulse rate is very stable and exactly known. This is important in any application where anything to do with time or exact measurement is crucial. It is relatively simple to make an oscillator that produces some sort of a signal, but another matter to produce one of relatively precise frequency and stability. AM radio stations must have a carrier frequency accurate within 10Hz of its assigned frequency, which may be from 530 to 1710 kHz. SSB radio systems used in the HF range (2-30 MHz) must be within 50 Hz of channel frequency for acceptable voice quality, and within 10 Hz for best results. Some digital modes used in weak signal communication may require frequency stability of less than 1 Hz within a period of several minutes. The carrier frequency must be known to fractions of a hertz in some cases. An ordinary quartz watch must have an oscillator accurate to better than a few parts per million. One part per million will result in an error of slightly less than one half second a day, which would be about 3 minutes a year. This might not sound like much, but an error of 10 parts per million would result in an error of about a half an hour per year. A clock such as this would need resetting about once a month, and more often if you are the punctual type. A programmed VCR with a clock this far off could miss the recording of part of a TV show. Narrow band SSB communications at VHF and UHF frequencies still need 50 Hz frequency accuracy. At 440 MHz, this is slightly more than 0.1 part per million. Ordinary L-C oscillators using conventional inductors and capacitors can achieve typically 0.01 to 0.1 percent frequency stability, about 100 to 1000 Hz at 1 MHz. This is OK for AM and FM broadcast receiver applications and in other low-end analog receivers not requiring high tuning accuracy. By careful design and component selection, and with rugged mechanical construction, .01 to 0.001%, or even better (.0005%) stability can be achieved. The better figures will undoubtedly employ temperature compensation components and regulated power supplies, together with environmental control (good ventilation and ambient temperature regulation) and " battleship " mechanical construction. This has been done in some communications receivers used by the military and commercial HF communication receivers built in the 1950-1965 era, before the widespread use of digital frequency synthesis. But these receivers were extremely expensive, large, and heavy. Many modern consumer grade AM, FM, and shortwave receivers employing crystal controlled digital frequency synthesis will do as well or better from a frequency stability standpoint. An oscillator is basically an amplifier and a frequency selective feedback network (Fig 1). When, at a particular frequency, the loop gain is unity or more, and the total phaseshift at this frequency is zero, or some multiple of 360 degrees, the condition for oscillation is satisfied, and the circuit will produce a periodic waveform of this frequency. This is usually a sine wave, or square wave, but triangles, impulses, or other waveforms can be produced. In fact, several different waveforms often are simultaneously produced by the same circuit, at different points. It is also possible to have several frequencies produced as well, although this is generally undesirable. In an oscillator, the feedback network determines the frequency and stability of the generated signal. Frequency is of course the number of cycles per unit time produced and is generally specified in Hz, kHz (1000 Hz), MHz (1 million Hz), or even GHz (1 billion Hz). Stability is another matter. What we are trying to express is how much the oscillator frequency will change in a certain amount of time. The key here is the length of time. Long term stability is generally expressed in frequency drift (delta F or ∆F) per unit time or specified time interval. Long term drift is caused by component aging due to electrical, thermal, physical, and chemical changes in components over a relatively long (100 hours or more) time period. This is generally, but not always, permanent. This is generally compensated for by readjustment ofcircuit parameters, either manually or automatically. Short-term stability is usually caused by component changes due to circuit heating, warmup, temperature fluctuations, and instability of components, both

Oscillators and operational amplifiers

A generalized approach to the design of oscillators using operational amplifiers as active elements is presented. A piecewise-linear model of the amplifier is used so that it make sense to investigate the eigenvalues of the Jacobian of the differential equations. The characteristic equation of the general circuit is derived. The dynamic nonlinear transfer characteristic of the amplifier is investigated. Examples of negative resistance oscillators are discussed.