need help in designing 10Mhz CMOS Oscillator

[Hitotsu]

cmos 10mhz oszillator

The Oscillator requirement:
C < 100ρF
R < 100MΩ
no crystal
no inductor

 

[Sadegh.j]

10mhz oscillator cmos

No Inductor -> Use a ring Osc
No Crystal -> The use of a PLL is not allowed

R and C limitations: Increase the number of stages instead of increasing the delay of stage so much

Good luck

 

[Hitotsu]

Thanks alot.

Can you guide me on how I should go about designing a ring oscillator

How many stage oscillator should i design to provide 10Mhz?
How the capacitor values affect my oscillator freq?

Thank you once again

 

[ombadei]

The ring oscillator looks good..

but how would one determine its maximum frequency? Are we to look at the propagation delay of the 'not' gate and hence, calculate how many odd stages are required to produce the desired frequency?

 

[kumarghz]

A odd series of Inverters which design using CMOS may help. Please use big size of transistor and many transistors in series.

regards,
Kumar

 

[krivan]

Hitotsu,

in this case I would use a simple ring oscillator as it has already been suggested. Put down odd number of inverters and with the variation of their vdd voltage the output frequency will change as well. This vdd is obviously not vdd!, which is the common positive rail.

So: odd number of inverters + change of their power supply -> frequency changes.

Good luck,
Krivan