# Which architecture is the best for highly linear VCO?

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#### svensl

##### Full Member level 1
I would like to design a VCO that exhibits an almost-linear relationship between input voltage and output frequency. The more linear the better. I was wondering which architecture (LC, ring oscillator, negative resistance….) would be most suited for such a task?
Is there any literature that talks specifically about and compares different structures for linearity?

Regards,
sven

#### xtasa

##### Member level 1
Re: highly linear vco

Hello Sven,

Your question is question general type or you have some specific frequency requirement. I made some extremely linear VCO voltage/frequency but is frequency depending solution.

Gl XTASA

#### svensl

##### Full Member level 1
Re: highly linear vco

At the moment the question is more general.
Eventually, I am interested in a center frequency of no more than 100MHz. For the gain (sensitivity) Kvco I would like to have a minimum a tenth of the center frequency. For example, f_0=50MHz, K_vco=5MHz. So over the 5MHz range the dependency on the voltage should be as linear as possible.

What architectures did you use and what methods did you apply to achieve highly linear VCOs?

Thanks,

#### jdlijj2

##### Newbie level 5
Re: highly linear vco

svensl said:
At the moment the question is more general.
Eventually, I am interested in a center frequency of no more than 100MHz. For the gain (sensitivity) Kvco I would like to have a minimum a tenth of the center frequency. For example, f_0=50MHz, K_vco=5MHz. So over the 5MHz range the dependency on the voltage should be as linear as possible.

What architectures did you use and what methods did you apply to achieve highly linear VCOs?

Thanks,

ring oscillator can match your req, the frequency is not so high so no need to use LC circuit. but you should modify it carefully
and the noise is a problem.

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