thanx man for helping, i tried crystal oscillator but i dont know how to model the crystal in a crystal oscillatort iam talking about the values of C1,C2,R1,RfDo you understand how the oscillator works at lower frequencies?
The Wiki for Colpitts Oscillator shows a complete circuit with values for a 50Mhz output, around halfway down the page.
If you need a very accurate signal source, try a crystal based oscillator.
i found this PDF (the PDF in the attachment) which say that for 1 MHZ crystal the feed back resistance should be from 5 to 10 MΩ and for 10MHZ crystal Rf should be from 1 to 5 MΩIn your Pierce oscillator above with the crystal, Rf should be around 1MΩ, and R1 should be 1k for LS series logic, up to 330k or more for CMOS (HC/HCT) based logic. C1 and C2 should be equal, typically between 20pF and 66pF.
You will want to buffer the output through another inverter so the load doesn't kill the oscillations.
If the clock is driving another IC or a long PCB trace/wire, the extra load may cause the amplitude or frequency of the oscillator to drift or stop completely. Essentially, the same effect as changing the value of R1 drastically.thanx for the reply , but could you explain to me plz why i need onther inverter ? cuz all the circuits i found it using 1 inverter only like post #4
I think 330k, in conjunction with C1 and C2, will cause WAY too much attenuation and phase shift at 60MHz.In your Pierce oscillator above with the crystal, Rf should be around 1MΩ, and R1 should be 1k for LS series logic, up to 330k or more for CMOS (HC/HCT) based logic. C1 and C2 should be equal, typically between 20pF and 66pF.
You will want to buffer the output through another inverter so the load doesn't kill the oscillations.
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