Oscillator design help!

[wangwang96]

I want to design a oscillator with 15MHz frequency output ,external resistor can be uesd,if I use tranditional RC oscillator ,the parasitic capacitor will affect precision of output frequency.if any other better structure ,please tell me,thanks a lot!

 

[sunking]

1. trimming
2. Crystal osc

 

[hung_wai_ming@hotmail.com]

Check out my previous answers. Check out patents from national or microchip. Again, if you do RC, never you can work out for a precise oscillator without final trimming. What you can do is to compensate for circuit, not for RC. however, if you have microcontroller, you can use register bits to step by step trim it without real trimming

 

[butterfish]

for RC oscillator, even triming used, frequency offset will be 2~3%, and also depends on temperature;

 

[iamxo]

do review of reported papers about OSC design.
there will be many ones.

like RC, Gm-C, and so on
then choose one after you compare with each other.

 

[acsreddy77]

You need to use crystal oscillator with external feedback resistor ( 1 to 10 Mohm).
Crystal has to be connected across simple inverter.
This will provide accurate frequency.

 

[sirk06]

a chain of inverters can be an option!

 

[jhan_wzx]

i think you have to have another external cap or you will not get an accurate oscillator without sunking's suggestion.
regards

 

[pankajdudulwar]

U can try the cross coupled configuration for oscillator .I think it's the best one available and as symmetry.
If u need any thing else let me know.

 

[IBO]

crystal osc. and harmonic gen. as a crystal osc. wid ur specified freq. is not found