L-C Oscillators

Author: N.H. Crowhurst

As well as amplifiers, to make audio waveforms larger, we also need oscillators to produce audio waveforms. They may be needed for testing, for electronic musical instruments, or for the high-frequency bias and erase in tape recording. In addition, they supply control frequencies needed for some kinds of automatic operation. In audio work, the exact waveform of the oscillation is important.

Voltage and current in a tuned circuit

There are three basic kinds of oscillators. One uses an inductor and capacitor in parallel to produce a tuned or resonant circuit in which energy passes between the inductor and capacitor at the resonant frequency of the circuit. All that is needed to use this circuit in an oscillator is to feed back enough energy to make up for that lost in every transfer due to the losses in the circuit. This is usually achieved by having the tuned circuit in either the plate or grid circuit of a tube and using the amplification of the tube to feed back some of the energy in the correct phase to maintain the oscillation.

Basic Oscillator Circuits