What is An Oscillator?

What is An Oscillator?

Oscillators are circuits that can transfer electrical energy from the DC power supply to AC electrical energy without external signaling at a certain frequency. Oscillator is called circuits that continuously output at the frequency at which it is set or at a fixed frequency.Oscillator

An oscillator is an integrated circuit that produces periodic AC output without applying the input signal in any way. There are many types. These species are named according to their structure and according to the output waveforms they produce. The word oscillator used here is a signal generator, which usually refers to the sine wave. In fact, an oscillator is an amplifier circuit that provides its own input signal.

Oscillators in general; sinusoidal oscillators and non-sinusoidal oscillators are divided into 2 classes. Sinusoidal oscillators produce signals such as sinusoidal signal at exit and non-sinusoidal oscillators such as square, rectangular, triangular and saw teeth. Oscillator circuits that produce square waves are also called "multivibrators".Oscillator

Oscillation What?

In electrical and electronic systems, electrical signals whose direction and intensity change in a certain order over time are called oscillation. It is undesirable to have a high oscillation rate at the exit of the circuit. For this purpose, various circuits are used to reduce oscillations. Examples of these circuits include active-passive electronic filters. However, in some systems, oscillation is a necessity. Therefore, circuits that produce oscillation signals are also needed. Oscillators are used in these circuits and the circuits are called oscillator circuits.

Types of Oscillators

RC OscillatorOscillator

Oscillators that produce sinusoidal signals at the output produce signals from low frequencies (several hertz), high frequencies (109 Hz). If resistance and capacitors are used for frequency detecting circuitry in low frequency oscillator types, such oscillators are called "RC OSCILLATORS". RC oscillators have a wide application area in the sound frequency field between 20 Hz and 20KHz.

LC OscillatorOscillator

High frequency oscillators that cannot be obtained with RC oscillators are obtained with LC oscillators. High frequency sinusoidal signals are obtained at MHz level with LC oscillators.The circuit consisting of parallel coil and capacitor is called "Tank Circuit". LC oscillators; There are also different types of Colpits oscillator, Hartley oscillator, Collector tuned oscillator Ticler oscillator.

Crystal Oscillator

Frequency stability is very important in oscillators. The ability of an oscilator to remain at a fixed frequency is called "Frequency Stability". Frequency stability is also not good with RC and LC oscillator. If an oscillator, a receiver or transmitter will operate at a fixed frequency, i.e. there will be no slight change in the frequency at which it operates, it is best to use crystal-controlled oscillators with the best frequency stability in the transmitter circuits to broadcast at the allocated frequency.

In RC or LC oscillators, frequency stability varies depending on environmental changes such as variability in L, C and R values, changes in the static working point of the transistor amplifier, temperature and humidity.


The circuits that produce the square, rectangular signal used as a trigger signal in digital circuits are called multivibrators. These circuits provide the required square wave signal, i.e. trigger signal, in our flip flop circuits. It is also possible to use multivibrators as memory elements. With these features, they form the basis of flip-flops. The nonstop burning and deflation of an LED connected to a circuit is called a flip-flop. The combustion of the LED is called flip, the deflation state is called flop.

Types of Multivibrators

Monostable Multivibrators

Monostable multivibrators give an output signal in the form of only a single pulse, depending on the mark applied to their input. These circuits are called one-shot. The duration of the output mark depends on the values of the timing (resistance and capacitor) elements to be connected from the outside. The duration of the trigger signal may be large or small, regardless of the output pulse. The duration of the output pulse may be wider than the input pulse. The following illustrator shows the monostable multivibrator circuit with transistor. The T1 transistor, which initially received horse polarity through R1 resistance, is in the transmission and the T2 transistor is in the cut. Meanwhile, the C capacitor will charge as in the figure. As soon as a positive trigger signal is given from the trigger entry, the T2 transistor will be discharged through the C capacitor R1 and T2 transistor, and the T1 transistor, which cannot receive the brain polarization, will go to the cut. This situation will continue until the capacitor discharges. When the capacitor discharges, the T1 transistor will re-transmit and the T2 transistor will go to the cut. This will be maintained until the next trigger signal.

Self-Employed (Astable) Multivibrators

Another type of multivibrator circuit is called astable multivibrator.They are circuits that change the situation in the periods determined by the timing elements from the moment the working voltage is applied. The Astable multivibrator is used as a square wave oscillator for trigger signaling purposes in timing circuits.

Dual Stable (Bistable) Multivertradors Oscillator

Circuits that maintain their condition are called double-stable multivibrators unless there is an external trigger signal.