Oscillators, Physics tutorial

Definition:

The oscillator gives the source of repetitive A.C. signal across output terminals without requiring any input (except D.C. supply). Signal generated by oscillator is generally of constant amplitude.

Wave shape and amplitude are determined by design of oscillator circuit and choice of component values. Frequency of output wave may be fixed or variable, depending on oscillator design.

Kinds of Oscillator:

Oscillators may be categorized by the kind of signal they generate.

  • Sine wave oscillators create sine wave output.
  • Relaxation oscillators and Astable multivibrators create Square waves and rectangular pulses.
  • Sweep oscillators create saw tooth waves.

Sine wave oscillators can also be categorized by frequency, or kind of frequency control they use. RF (radio frequency) oscillators working at frequencies above approx 30 to 50kHz use LC (inductors and capacitors) or Crystals to manage their frequency. These may also be categorized as HF, VHF, and UHF oscillators, depending on frequency.

LF (low frequency) oscillators are usually utilized for producing frequencies below approx 30 kHz and are generally RC oscillators, as they utilize resistors and capacitors to manage their frequency.

Square wave oscillators like relaxation and astable oscillators may be utilized at any frequency from less than 1Hz up to several GHz and are very frequently implemented in integrated circuit form.

Sine Wave Oscillators:

These circuits ideally generate pure sine wave output having constant amplitude and stable frequency. The kind of circuit utilized depends on number of factors, comprising frequency required. Designs based on LC resonant circuits or on crystal resonators are utilized for ultrasonic and radio frequency applications, but at audio and very low frequencies physical size of resonating components, L and C would be very big to be practical. Therefore combination of R and C is utilized to control frequency.

LC oscillators:

Inductors and capacitors are combined in the resonating circuit which generates a very good shape of sine wave and has fairly good frequency stability. That is, frequency doesn't modify very much for changes in D.C. supply voltage or in ambient temperature, but it is comparatively simple, by using variable inductors or capacitors, to make variable frequency (tuneable) oscillator. LC oscillators are widely used in producing and receiving RF signals where variable frequency is needed.

Relaxation oscillators:

These oscillators work on the different principle to sine wave oscillators. They generate square wave or pulsed output and usually utilize two amplifiers, and frequency control network which just creates a timing delay between two actions. Two amplifiers operate in switch mode, switching fully on or fully off alternately, and as time, during which transistors are really switching, only lasts for very small fraction of each cycle of wave, rest of the cycle they relax while timing network generates remainder of wave.

Sweep oscillators:

Sweep waveform is another name for the saw-tooth wave. This has linearly changing (e.g. increasing) voltage for approximately the whole of one cycle followed by the fast return to wave's original value. This wave shape is helpful for changing (sweeping) frequency of voltage-controlled oscillator that is oscillator which can have its frequency varied over the set range by having variable sweep voltage applied to control input. Sweep oscillators frequently comprise of ramp generator which is basically a capacitor charged by the constant value of current.

Significance of oscillators:

Oscillator is essentially considered to be technical indicator which is utilized to produce repetitive signals. In technical terms, one can say that oscillator has a path where part of output signal is fed back to produce input signal. Or oscillators have capacity to generate output signals without input signal.

On the basis of output signals generated by oscillators, they are essentially classified in two classes, i.e. harmonic oscillators and relaxation oscillators. And most common kind of waveform generated by oscillators is sinusoidal and square.

They come in different packages and each has its own functionality and characteristics to offer. Thus, you must be quite careful while selecting oscillators. Oscillation is periodic variation and people frequently consider similar to vibration. Oscillation is the process which not only exists in physical world but in biological world as well.

Usage of oscillators has increased gradually. Nowadays, they are usually found in almost all electronic, most commonly in everyday circuits. Basic feature of oscillators to produce oscillating output is utilized to produce signals in electronic products. Different outputs which can be generated by oscillators are square, sine, saw tooth, triangle or complex waveform.

Principle of Oscillators:

The oscillator comprises of the amplifier and feedback network. Basic components are needed to get oscillations are given below:

  • Active device either Transistor or Op Amp is utilized as amplifier.
  • Feedback circuit with passive components like R-C or L-C combinations.

To begin oscillation with constant amplitude, positive feedback is not only enough condition. Oscillator circuit should satisfy following two conditions called as Barkhausen conditions:

1. first condition is that magnitude of loop gain (Aβ) should be unity. This signifies product of gain of amplifier 'A' and gain of feedback network 'β' has to be unity.

2. Second condition is that phase shift around loop should be 360° or 0°. This signifies, phase shift through amplifier and feedback network has to be 360° or 0°.

Applications of the Multi wave oscillators:

Healing action of MWO is very broad because of fact that it is holistically at work. Healing process takes place in all parts of body. Multi-Wave-Oscillators are utilized in several countries worldwide by therapist and individuals and it is effectively applied to:

Electro stress afflictions:

Pain in neck, shoulders, lower back, tennis elbows and so called pinched nerves and infected tendons, and slipped disk (Hernia).

Additional applications by:

Rheumatic arthritis, Rheumatism, arthritis, heart rhythm disorders, headaches, infections, migraines, and chronic fatigue syndrome and several more other afflictions.

Cancer and tumors:

Some results indicate that the Multi-Wave-Oscillators can be applied also with the treatment of cancer and tumors, but further research will indicate into how effective it is.

Oscillators are significant in several different kinds of electronic equipment. For instance, quartz watch uses quartz oscillator to keep track of what time it is. The AM radio transmitter utilized oscillator to generate carrier wave for station, and AM radio receiver utilized special form of oscillator called resonator to tune in station. There are oscillators in computers, metal detectors and even stun guns.

Other Applications:

Crystal oscillators are utilized in several electronic applications. Few of these applications are Military and Aerospace, Communications, Electronic warfare, Fuses, Guidance systems, IFF (Identification Friend or Foe), Navigation, Radar, Sensors and Sonobuoys.

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