What is VCO : Voltage Controlled Oscillator

A Voltage Controlled Oscillator (VCO) is an electronic oscillator whose output frequency varies according to an applied control voltage. VCOs are fundamental components in phase locked loops, frequency synthesizers, wireless communication systems, radar equipment and signal generation circuits where dynamic frequency adjustment is required. Let us understand its function and types of implementations.

Oscillators whose frequencies are controlled using an external input DC voltage are referred to as VCOs. The full form of VCO, as mentioned, is Voltage Controlled Oscillator.

A voltage control crystal oscillator is known as VXO. They are used in applications where voltage to frequency conversion is needed. They are also used in FM modulators and RF synthesizer designs.

Refer to RF Synthesizer Design which uses a VCO in its applications.

There are many ways VCOs can be constructed:

• Implemented using discrete transistor and varactor diode circuits in high-frequency applications.
• Implemented using IC with RC multi-vibrator. Here, frequency is controlled using a wide range of AC/DC input voltages. These low-frequency VCOs have a frequency range of operation from 1 Hz to about 1 MHz. Normally, IC NE566 is used for such applications.

The figure above shows IC NE-566 used as an FM modulator application. The center frequency of the circuit is set using R1 and C1. RF carrier frequencies up to 1 MHz can be used with this VCO circuit.

VCO is also referred to as SCO. The full form of SCO is SubCarrier Oscillator.

Continue Learning Voltage Controlled Oscillators (VCO)

Deep dives into how voltage-controlled oscillators generate frequencies, how they are tuned, and how they integrate with PLLs.

• Voltage Controlled Oscillators (VCOs) Overview
• VCO Tuning Constant and Tuning Methods
• Difference Between VCO and PLL
• NCO vs VCO: Understanding the Differences
• VCO vs VCXO Differences
• MAX2871 Wideband PLL/VCO IC: Pin Diagram and Applications

Continue Learning Oscillator Fundamentals & Types

• Oscillator Types
• Numerically Controlled Oscillator (NCO) and its use in DDS Design
• Understanding YIG Oscillators
• Backward Wave Oscillators (BWO): Advantages & Disadvantages
• OCXO SC Cut Crystal Oscillator: Advantages & Disadvantages
• Understanding Oven-Controlled Crystal Oscillators (OCXO)

Compare Oscillator types - OCXO, Crystal, MEMS

• 3 Types of OCXO : Difference between AT, IT & SC cut crystals
• Difference Between a Crystal and an Oscillator
• Crystal vs Resonator Differences
• MEMS Oscillator vs Crystal Oscillator
• OCXO vs Rubidium Oscillators
• Mechanical vs Electrical Oscillators
• OCXO vs VCXO vs TCXO vs DCXO : Key Differences