VCO modulating voltage input

I have RF VCO module. I have 2 inputs Vcc (Power supply at 5V). Then I have modulating signal 0-4.5V. What should I do with the modulating signal? Can I short it to the GND (The GND on the VCC)? What is the modulating signal for? It is 1.2GHz VCO module. I need the VCO to be in the Box. It is not for a bench testing. If anybody have a reference for VCO book or manual that would be great. Thanks

by TheTraveler2025
December 03, 2021

That depends on the VCO that you use. You can have two Vcc pins if the IC has two VCO (a dual VCO chip).Some VCO produce a sinus wave, some a rectangular wave, some two complementary rectangular waves (both with a duty cycle of 50%). In any cases, it could be unwise to connect it to the ground or to Vcc without a load (resistor). The names of the "pins" are not standardized. As example, Analog Devices call the input voltage, governing the output frequency, Vtune. You should check the datasheet of your VCO for more specific details.

As a side note, you can built a VCO with a 555 (even if I doubt that it will be temperature independant and power friendly): 555 VCO circuit

by vanderghast
December 04, 2021

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