What is a voltage controlled oscillator and what does it look like?

[unbuildpain]

What is a voltage controlled oscillator and what does it look like?

On online tutorials, I keep coming across this VCO or voltage controlled oscillator, what is it? What does it look like? Or is it a custom circuit I have to build? Can it be made to oscillate to any frequency or is there a limit?

 

[wwfeldman]

a voltage controlled oscillator is exactly what is says
it is an oscillator - that is, it produces sin or square waves at some frequency
the frequency is controlled by an input voltage
for example, the control voltage may run from 0 to 10 V and it may produce a frequency from 1kHz to 25 kHz

i was using one about 30 years ago that was a 16 pin DIP - about 0.3 inches wide and about 1.6 inches long, about 1/4 inch high

each VCO has a frequency range over which it can be adjusted, according to its control voltage range

 

[KlausST]

Hi,

Why don't you do a simple internet search on your own?
You will find descriptions, example circuits discrete and integrated and specifications...

In short:
* Oscillator = frequency generator
* voltage controlled = input voltage determines output frequency

Is there a limit?:
* can the input voltage be unlimited high = infinite ( like million volts) ? --> no
* can the output frequency be unlimited high? --> no

Klaus

 

[unbuildpain]

Hi,

Why don't you do a simple internet search on your own?
You will find descriptions, example circuits discrete and integrated and specifications...

In short:
* Oscillator = frequency generator
* voltage controlled = input voltage determines output frequency

Is there a limit?:
* can the input voltage be unlimited high = infinite ( like million volts) ? --> no
* can the output frequency be unlimited high? --> no

Klaus

Before actually asking here, I searched Google and all the images it showed were of schematics of circuits. I got confused if it was a part or circuit.

What is highest voltage and frequency oscillation cheap ones support?

 

[d123]

Hi,

I had a look recently at standard parts, of the few I looked at the datasheets of some were max. ~10V, some were ~30V. It depends how old the IC design is.

XR2209 is a typical/classic (old, obsolete-ish) VCO. The link is to the datasheet on Farnell, have a read, it's an easy one to start with.

 

[unbuildpain]

Hi,

I had a look recently at standard parts, of the few I looked at the datasheets of some were max. ~10V, some were ~30V. It depends how old the IC design is.

XR2209 is a typical/classic (old, obsolete-ish) VCO. The link is to the datasheet on Farnell, have a read, it's an easy one to start with.

Thanks. Can those be used to create 350MHz to 5GHz?

 

[d123]

... I'd guess ~1 MHz - maybe - for cheap ones but may be wrong.

I found the problem was not highest voltage or frequency but that they generally need 'too high' a supply voltage and can require 'too much' supply current for low-power, low-voltage circuits.

You can experiment with op amp versions yourself to get a basic idea, most op amp cookbooks have at least a 'lab signal generator' schematic and some are adjustable.

 

[ZASto]

Thanks. Can those be used to create 350MHz to 5GHz?

Nah, to low, It goes above 3.2 THz

 

[d123]

Thanks. Can those be used to create 350MHz to 5GHz?

Not the ones I saw, they were old and 'slow'.

Do a parametric product search of VCOs on suppliers' and manufacturers' websites to see if anything matches your needs.

 

[unbuildpain]

Nah, to low, It goes above 3.2 THz

Why do you think it goes over 3.2THz? Are you trolling?

 

[BigBoss]

If you need a VCO that will work between 350 MHz-5GHz, it's not possible to design and build up such VCO with this huge wide-band.
VCOs have generally max. 2 octaves bandwidth or less.If you intend to use that frequency band, you have to use a VCO which works at highest frequency then you should divide this frequency by aid of divider but finding a discrete divider for that band is so difficult.
Best option is to use PLL+VCO ICs of Analog Devices ( or similar circuits of any other manufacturer ).

LTC6948 Datasheet and Product Info | Analog Devices

The LTC6948 is a high performance, low noise, 6.39GHz phase-locked loop (PLL) with a fully integrated VCO, including a reference divider, phase-frequency detector (PFD), ultralow noise charge pump, fractional feedback divider, and VCO output divider.The fractional divider uses an advanced, 4th...

www.analog.com

Or using multiple VCOs together with switching circuit to achieve desired frequency and signal.
There are many cost effective ready-to-use PLL+VCO circuits in the market.

 

[wwfeldman]

google is not really the best place to search for available components
try a distributor like DigiKey, Mouser, Newark (or Farnell in UK), Jameco ; there are other distributors
each has its advantages and disadvantages
they have search engines - i like DigiKey's search process

 

[ZASto]

Why do you think it goes over 3.2THz? Are you trolling?

Nope, have you seen a smiley?

Read The F.... Datasheet for the chip. Everything is written there