General explanation of the oscillator and Oscillator Types

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Oscillators are the basic components forming circuit called a clock and a timer circuit (Timing) as well as a series of generating / signal describing mathematical functions programmed into the system. Oscillator is also an electronic device that produces output with no signal voltage. In the electronic communications system oscillator can not operate without a source of sinusoidal electric wave. Many types of oscillator circuits are used to produce a sinusoidal wave, and only a few of the commonly used by many people. Wave is in Layer Cathode Ray Tube (CRT Layer) will be analyzed on the oscillator in order to illustrate the methods commonly used. Since the oscillator is one of a series of clock and has a timing properties, the oscillator can be divided into various kinds of bridge RC oscillator, wien bridge oscillator, and the oscillator T-twin. In the oscillator can be determined pr-conditions for the oscillator is a positive feedback loop and voltage gain.

In the use of oscillators, we would know the Timer IC 555 which is a fundamental component in the practice oscillator. Timer IC 555 is one of the most versatile integrated circuit chip ever produced. 555 timer IC is not just a mix of analog and digital circuits are neat, but also the application of the circuit are virtually unlimited in the world of digital pulse generation. This tool can also be an excellent case study for the newcomers in the world of electronics as a tool incorporates some of the concepts and techniques that are important. Basically, the device consists of two operational amplifiers are used as a differential comparator and RS bi-stable element. Standard 555 timer is stored in an 8-pin DIL package sources and work from the source voltage between 4.5 V and 15 V.

Oscillator is an electronic device that produces the output of the voltage signals. Shape cues voltage versus time was different, that is forms sinusoid, square, triangle, sawtooth, or pulse. Different oscillator amplifier, therefore requiring the amplifier input signals to produce output signals. In the oscillator no input signal, only the output signal only, the frequency and amplitude can be controlled. Often an amplifier accidentally generate a frequency output without input whose value can not be controlled. In this case, the amplifier is said to oscillate. Oscillator is widely used as a source of cues to test an electronic circuit. Oscillator is usually called a generating signal, or if the function generating output signal can take many different forms. Oscillator is also used on radio and television transmitters, as well as in radio communications, microwave, and optics to generate electromagnetic waves that can be boarded for information. Radio and television receivers also use the oscillator to process signals coming. This gesture came mixed with signals from a local oscillator to produce an information carrier signal with a lower frequency. This last gesture is known as a signal if (intermediate frequency).

Oscillator is also used to detect and determine the distance to the microwave (radar) or ultrasound (sonar). Furthermore almost all digital devices such as watches, digital calculators, computers, computer helper tools, and so forth using an oscillator. So, it is clear oscillator plays an important role in the electronic world. There are basically three kinds of oscillators, ie RC oscillator, LC oscillator, and relaxation oscillator. The first two signals produces sinusoidal shape whereas relaxation oscillator signal generating square, triangle, sawtooth or pulse.

RC oscillator. An oscillator with a resistance R and capacitance C to set the frequency. Signaling can be assured that the resulting sinusoidal shape. Oscillator using positive feedback that is reactive, so that the condition of the oscillator, which is only valid for a single frequency value, resulting sinusoidal output signal. 

Wien bridge oscillator. An improvement than the RC oscillator as a new bridge will be covered are bridge oscillator Wien. Wien bridge oscillator can be controlled using an automatic gain control (AGC-Automatic Gain Control) in order to have a fixed amplitude versus time. One problem that arises in RC oscillator is the oscillator stability. An oscillator is said to be stable if the amplitude of the output signal continues to rise and eventually cut or depressed oscillation signal so it does not come out. Discussion of stability oscillator requires understanding of control theory, but here can be summed up by the following. If the gain is less than 3, the oscillations would off and if more than 3, the output signal will continue to grow so truncated. As a result, the output is no longer sinusoidal. 

Oscillator T-Twins. T-Twins is a series of the amplitude of the T-twin is a filter that forwards the tape seal all frequencies except within a frequency band around 1/RC. RC oscillator is used to generate a low-frequency sinusoid signal, ie below 500 KHz. RC oscillator does not use inductors, and the frequency can be changed by adjusting the resistance of a potentiometer. In this chapter we can discuss about the LC oscillator, the oscillation obtained through parallel LC circuit. LC oscillator is used to obtain a sinusoidal signal of audio frequency to radio frequency, even microwave frequencies. Hartley oscillator can be switched on and off at regular intervals by a series resistor and a capacitor, so that the oscillator can produce sounds similar to the sound of chicks. The emergence of the sound can be explained as any unfilled electric charge capacitor, the oscillator works to produce sound. Charged capacitor voltage and charge through the resistor so that the voltage at the base will rise. A transistor voltage exceeds 0.6 volts, the transistor will saturate so that the oscillation stops. At the same time a sudden change in flow will result in induced voltage L1, which will also lead to the opposite voltage L2. As a result, the positive charge the capacitor to be drawn through the second capacitor so empty. At that time the oscillator to work again to produce the sound. Thus continue to occur repeatedly. Another modification of a Hartley oscillator is used for the FM microphone.

Crystal Oscillator. In order to obtain a stable frequency people use crystal oscillator circuit. The meaning is crystal quartz crystal oscillator, the crystal of silicon dioxide. These crystals are piezoelectric. Piezoelectric properties are properties of several kinds of crystal, if the crystal is pressed, pressed between two surfaces that will arise different voltage. Conversely, if the crystal surface between two given electric potential difference will occur between the two surfaces of the mechanical stress that causes changes in the crystalline form. The nature of the resulting crystals of quartz crystal behaves as a resonant system. Curvature of the crystal resonance is very sharp, or have very high load factors (in the order of thousands). Crystal resonant frequency depends on the thickness of the crystal, and the direction of the field of cutting crystal oscillation to determine the strength and frequency of temperature changes.

Relaxation Oscillator. Shape signal released by the relaxation oscillator sinusoid formless, but may be a square, pulse, triangle, or sawtooth. Relaxation oscillator using charging and strengthening the charge on a capacitor through a resistance. A change that occurs exponentially in time called relaxation. Therefore, by charging a fixed voltage that is exponential, then the oscillator that uses this mechanism is also known as a relaxation oscillator. Relaxation oscillator can be made ​​using fluorescent lamps, single connection transistor uni junction transistor (UJT), PUT, op-amps, and transistors. Neon relaxation oscillator can be used as a small fluorescent lamps are often used in pen-test or panel lights. Fluorescent lamps containing neon gas at very low pressure. Above a certain voltage neon lights and neon lamp resistance becomes very small. This occurs because the neon lights are caused by the ionization of neon gas between two poles. UJT oscillator. UJT or Uni Junction transistor is an active component that is widely used to produce a pulse signal. These pulses are used to control the instrumentation. UJT widely used to set the SCR and the Triac, the semiconductor component that functions as tiration using pulses generated by the base current UJT. Schmitt Trigger oscillator using a hysteresis in the transfer function Schmitt trigger.

Multivibrator. There are many instances where we need the square wave output of an oscillator instead of sine wave output. Multivibrator is a type of oscillator circuit that generates an output waveform consists of one or more square pulses. The name "multivibrator" stems from the fact that such a waveform is rich in harmonics, namely 'plural Vibrations' / 'Multiple vibrations'. Multivibrator using regenerative feedback (positive), the active devices in the oscillator circuit works as a switch, alternately experiencing cut-off and saturation. The main types of multivibrator is:

• Stable multivibrator which provides a continuous circuit pulses (the device is sometimes referred to as a free-running multivibrator).
• Monostable multivibrator which produces a single output pulse (the device has a stable condition and is therefore referred to as a series of one-shot).
• Bi-stable multivibrator has two stable condition and requires a trigger pulse or a control signal to change from one condition to the other conditions.

Electronic communication system can not operate without electricity sinusoidal wave source. Many types of circuit used to produce sinusoidal oscillator, and only a few of the commonly used will be analyzed, in order to illustrate the general method.

Another LC oscillator. Colpitts oscillator is the most widely used LC oscillator. The capacitive voltage division resonant circuit is the right way to develop a voltage feedback. But many other types of oscillator can also be used.

Reference

1. Komunikasi Elektronika by Chairman Jakarta: Rineka Cipta
2. Rangkaian Elektronika by Sutanto Jakarta :Universitas Indonesia
3. Elektronika Teori Dasar dan Penerapannya by Sutrisno Bandung :ITB