In Frequency-Shift Keying (FSK) demodulation, a voltage-controlled oscillator (VCO) is often used to generate the output signal based on the frequency variations in the input signal. The voltage threshold for triggering the VCO in FSK demodulation is not a fixed value, but rather it depends on the specific design and requirements of the demodulation circuit.
The voltage threshold for triggering the VCO would be set based on factors such as the frequency separation between the two FSK signal frequencies, the sensitivity of the VCO to input voltage changes, noise levels in the system, and the desired demodulation performance.
In FSK demodulation, the VCO will typically be designed to respond to frequency changes in the input signal by varying its output frequency. The threshold at which the VCO switches between the two frequencies would be determined by the demodulation circuitry and the characteristics of the VCO itself. This threshold might be set by adjusting biasing or control voltage levels within the VCO circuit.
For accurate and reliable demodulation, the threshold should be chosen carefully to ensure that the VCO responds appropriately to changes in input frequency. The specific value of this threshold can vary from one implementation to another, and it's usually determined through experimentation, simulation, or careful analysis of the system's requirements.
If you're working on a specific FSK demodulation circuit or project, it's recommended to consult the documentation or specifications for that circuit or system to determine the appropriate voltage threshold for triggering the VCO.