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Design >> RF Design >> Synthesizer Vs VCO
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Message started by uzmeed on Jan 30^th, 2006, 10:54pm

Title: Synthesizer Vs VCO
Post by uzmeed on Jan 30^th, 2006, 10:54pm

Hi

I want to ask some thing very simple

wat are the demerits /merits of a synthesizer aginst a VCO

uzmeed

Title: Re: Synthesizer Vs VCO
Post by Juan F. on Mar 1^st, 2006, 8:37am

The typical Synthesizer composed by a PLL is a close loop circuit, it means that a frequency synthesizer is more robust again any VCO variation due to noise, temperature, process. Usually the FS consumes more power and area but in many applications the degree of accuracy in the generated signal impose you to use a PLL.

Title: Re: Synthesizer Vs VCO
Post by judean1 on Mar 21^st, 2006, 3:10am

Hi,
Synthesizer is a closed loop system where as the VCO an open loop, quite obvious answer.
Looking at the implementation part of the VCO, you would require a bank of voltage sources, if you wanted to change the frequency output. Synthesizer vaoids this problem by being a closed loop aystem. If fixed frequency is your requirement then one can make a VCO and keep the voltage constant.
There are certain architectures which compensates for the temperature, power supply variation effect on an oscillator, but this requires a synthesizer.
Noise output of the oscillator is of main concern, whatever may be the application. Possibility of having reduced noise can be achieved by using differential arcitectures of the VCO and having self biasing techniques for the same, so as to achieve more power supply noise rejection.
hope this helps.
Regards,
V