Voltage Controlled Oscillator

What does Voltage Controlled Oscillator mean?

A Voltage Controlled Oscillator (VCO) is an electronic circuit that generates an oscillating signal whose frequency can be controlled by varying a voltage. They are used in a wide range of applications, from simple tone generators to complex synthesizers.

VCOs are constructed using a Variety of circuit topologies, but the most common type is the LC oscillator. This type of oscillator uses an inductor (L) and a capacitor (C) to create a resonant circuit. When a voltage is applied to the circuit, it causes the inductor to store energy in its magnetic field and the capacitor to store energy in its electric field. The energy flows back and forth between the inductor and capacitor, causing the circuit to oscillate at a frequency determined by the inductance (L) and capacitance (C) values.

The frequency of the VCO can be varied by changing the voltage applied to the circuit. This is typically done using a voltage-controlled amplifier (VCA), which is an amplifier whose gain is controlled by a voltage. When the voltage applied to the VCA is increased, the gain of the amplifier increases, causing the frequency of the oscillator to increase. Conversely, when the voltage applied to the VCA is decreased, the gain of the amplifier decreases, causing the frequency of the oscillator to decrease.

Applications

VCOs are used in a wide range of applications, including:

• Tone generators: VCOs are used in simple tone generators to create a variety of different sounds. The frequency of the VCO can be controlled by a knob or other control, allowing the user to change the pitch of the sound.
• Synthesizers: VCOs are used in synthesizers to create complex sounds. By combining multiple VCOs and using different waveforms, synthesizers can create a wide range of sounds, from classic analog sounds to modern digital sounds.
• Frequency modulation (FM) synthesis: VCOs are used in FM synthesis to create sounds with a rich, metallic character. FM synthesis works by modulating the frequency of one VCO (the Carrier) with the output of another VCO (the modulator). The resulting sound has a characteristic “warbly” sound that is often used in electronic music.
• Phase-locked loops (PLLs): VCOs are used in PLLs to Lock the frequency of an oscillator to a reference signal. PLLs are used in a variety of applications, including clock generation, frequency synthesis, and signal conditioning.

History

The first VCO was developed in the 1930s by Edwin Armstrong. Armstrong’s VCO was a vacuum tube oscillator that used a Variable capacitor to control the frequency. VCOs became increasingly popular in the 1960s with the development of the transistor. Transistor VCOs were smaller, more reliable, and more efficient than vacuum tube VCOs, and they quickly became the preferred type of VCO for use in electronic music and other applications.

In the 1980s, digital VCOs were developed. Digital VCOs use digital techniques to control the frequency of oscillation. Digital VCOs offer a number of advantages over analog VCOs, including higher precision, lower noise, and wider frequency ranges. Digital VCOs are now used in a wide range of applications, including telecommunications, instrumentation, and audio synthesis.