Oscillators are a type of circuit found in many types of electronic equipment, including clocks, radios and computers.

An electronic oscillator is a circuit that produces a repetitive electronic signal, often a sine wave or a square wave. Oscillators are important in many types of electronic equipment, including clocks, radios and computers. There are two main types: the harmonic oscillator and the relaxation oscillator. This tutorial illustrates a type of relaxation oscillator called an LC oscillator or tank oscillator, and involves an inductor and a capacitor.

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Capacitor by moving the Switch Position slider to the "Battery" position; the Knife Switch closes to create a circuit between the battery and capacitor. Electrons (depicted as yellow particles) flow from the negative terminal of the battery to the capacitor (electrons flow opposite conventional current). The electrons stop when the capacitor has reached its capacitance for storing electricity. For every electron absorbed by the negative plate, a positive charge (depicted by red particles) appears on the opposite plate. Between the plates, which are divided by an insulating dielectric, an electrostatic field is maintained.

Next, move the switch position slider to the "Inductor" position. This creates a new circuit connecting the newly charged capacitor to the Inductor, a solenoid coil. The capacitor discharges electrons, which pass through the inductor as they rush to the opposite plate of the capacitor. As the electric current passes through the inductor, it produces a magnetic field (represented by blue lines) due to electromagnetic induction. (As this magnetic field grows, it retards somewhat the flow of electrons through the inductor due to Lenz’s Law – an effect not seen here but illustrated in our tutorial on EMF in Inductors). This field swells then subsides as the electrons stream through the inductor on their way to the oppositely charged plate of the capacitor, turning what had been the positive side of the capacitor into the negative side.

The path then reverses, as electrons are attracted from the newly charged negative plate of the capacitor to the positive plate, passing through the inductor on their way. This process goes through a few rounds, with the current subsiding gradually due to resistance in the circuit.


Thanks to our scientific advisor on this page, James Andy Powell, head electronics engineer in the MagLab's Instrumentation & Operations division.

Last modified on 7 January 2015