What is the term used for the oscillator stage in a frequency synthesizer?

The term used for the oscillator stage in a frequency synthesizer is referred to as the Voltage-Controlled Oscillator (VCO). A VCO generates an output frequency that can be varied by changing the input voltage, making it crucial for producing a range of frequencies. This capability is essential in synthesizers, as it allows for fine-tuning and adjustment of frequencies as needed.

In the context of a frequency synthesizer, the VCO is responsible for generating the desired signal after being controlled by feedback from phase-locked loops, ensuring that the output remains stable and synchronized with a reference frequency. The importance of the VCO in this context highlights its role in maintaining accurate frequency output, which is a key aspect of high-performance communication systems.

Although other terms, such as the phase-locked loop, are related to the frequency synthesizer's function, they represent broader concepts that encompass more than just the oscillator stage. The LC oscillator is a specific type of oscillator that can be used within a VCO but does not specifically denote the voltage-controlled aspect critical for frequency synthesizers. Lastly, the term VFO (Variable Frequency Oscillator) is more general and does not necessarily imply voltage control, thus making VCO the most appropriate term in this particular context