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What is an Oscillator Circuit?

An oscillator is a circuit that generates a continuous, repeated, and alternating waveform without any input. Essentially, oscillators convert unidirectional current flow from a direct current source into alternating current which is the desired frequency for a majority of operations. In this blog, we will outline oscillator circuits, their various types, and their differing applications.

To better understand oscillators, you must analyze the behavior of an LC tank circuit, or resonant circuit. Within this circuit, an inductor (L) and a completely pre-charged capacitor (C) are its main components. To begin, the capacitor discharges via the inductor, which converts its electrical energy into an electromagnetic field that can be stored in the inductor. Once the capacitor completely discharges, no current flow will be present in the circuit.

At this point, the stored electromagnetic field has produced a back-EMF which enables the flow of current through the circuit in the same direction as before. This flow continues until the EMF collapses which results in the back-conversion of electromagnetic energy into an electrical form, making the cycle repeat itself. However, the capacitor is charged with the opposite polarity depending on which one gets an oscillating waveform as the output.

The resulting oscillations that arise due to the interconversion between the two energy forms cease as they are subjected to the effect of energy loss from the resistance of the circuit. The amplitude of these oscillations decreases until it reaches zero. In order to acquire oscillations that are steady and continuous, one must compensate for the loss of energy. More than that, the energy supplied should be controlled with accuracy and must be equal to that of the energy lost.

If the energy supplied is more than the energy lost, then the amplitude of the oscillations will increase, creating a distorted output. In contrast, if the energy supplied is less than the energy lost, then the amplitude of the oscillations will decrease, leading to unsustainable oscillations. In simplistic terms, oscillators are amplifier circuits that provide negative or regenerative feedback where a part of the output signal is fed back to the input.

In this instance, the amplifier contains an amplifying active element that can either be a transistor or an Op-Amp. Meanwhile, a back-fed in-phase signal is responsible for maintaining the oscillations by making up for the losses in the circuit. When the power supply is switched ON, the oscillations are initiated in the system due to the electronic noise present in it. This noise signal makes its way around the loop, gets amplified, and converges to a single frequency sine wave very quickly.

Types of Oscillators & Applications

There are many types of oscillators, though most can be roughly categorized into two main categories: linear oscillators and relaxation oscillators.

In linear oscillators, also known as harmonic oscillators, the energy flow comes from the active components to passive components, and the frequency of oscillations is determined by the feedback path.

In relaxation oscillators, on the other hand, the energy is exchanged between the active and passive components, and the frequency of oscillations is decided by the charging and discharging time-constants involved in the process. Finally, linear oscillators produce low-distorted sine-wave outputs while relaxation oscillators generate non-sinusoidal waveforms.   

When your operations necessitate a specific frequency of a signal, oscillators are viable options. It is important to note that the frequency of oscillation can be varied by adjusting the component value with potentiometer arrangements. Some common applications of oscillators include quartz watches, which use crystal oscillators, alarms, metal detectors, radio, and more.


If you need voltage controlled oscillators, resonators, amplifiers, or other related circuit components, rely on ASAP Semiconductor. ASAP Semiconductor is a premier distributor of countless top-quality electronic parts, all of which are subjected to varying levels of quality assurance measures, tests, and verifications. Kickoff the procurement process with a competitive quote which can be accessed via our Instant RFQ service and see why customers choose us for all of their operational needs!


October 13, 2021

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