Voltage-controlled oscillator

A voltage-controlled oscillator (VCO) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscillation frequency. Consequently, a VCO can be used for frequency modulation (FM) or phase modulation (PM) by applying a modulating signal to the control input. A VCO is also an integral part of a phase-locked loop. VCOs are used in synthesizers to generate a waveform whose pitch can be adjusted by a voltage determined by a musical keyboard or other input.

A voltage-to-frequency converter (VFC) is a special type of VCO designed to be very linear in frequency control over a wide range of input control voltages.^[1]^[2]^[3]

Linear or generate a sinusoidal waveform. Harmonic oscillators in electronics usually consist of a resonator with an amplifier that replaces the resonator losses (to prevent the amplitude from decaying) and isolates the resonator from the output (so the load does not affect the resonator). Some examples of harmonic oscillators are LC oscillators and crystal oscillators.

harmonic oscillators

can generate a sawtooth or triangular waveform. They are commonly used in integrated circuits (ICs). They can provide a wide range of operational frequencies with a minimal number of external components.

Relaxation oscillators

VCOs can be generally categorized into two groups based on the type of waveform produced.^[4]

(LFO)

Low-frequency oscillation

Modular synthesizer

(NCO)

Numerically-controlled oscillator

(VFO)

Variable-frequency oscillator

Variable-gain amplifier

(VCF)

Voltage-controlled filter

. Ian Purdie's Amateur Radio Tutorial Pages. Archived from the original on 2019-01-04. Retrieved 2018-01-28.