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Help me solve problem in ring oscillator design that uses inverters

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akash_joshi

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Hi,

i am trying to design a ring oscillators using the inverters . I have connected 7 inverters in cascade and the output of last is connected to input of 1st.
I am trying to design it in 180nm technology and to output of each inverter i have connected a capacitor of 400 fF.
I am not getting the sustained oscillations and im not able to understand why?
If someone help .........It will be great
 

Re: Design related Query

The simulator is likely finding the circuit's "DC operating point," the point at which all 7 inverters are in their forbidden region (it's a point of unstable equilibrium). A tiny bit of noise would cause it to oscillate.

Try setting your simulator to skip the DC operating point, and set an initial condition (such as, set the 1st inverter's input to 0V).
 

Re: Design related Query

Im using Cadence Virtuoso as the design environment ............Can we set initial condition in it.
 

Re: Design related Query

I'm not familiar with Cadence Virtuoso, but a quick Google search presents this result: Click here. In this tutorial, the author is simulating a ring oscillator as well. If you want to skip to the part discussing initial conditions, just search the page for "initial" and you'll find it immediately.

Hope this helps.
 
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    jasonc2

    jasonc2

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Re: Design related Query

ZekeR said:
I'm not familiar with Cadence Virtuoso, but a quick Google search presents this result: Click here. In this tutorial, the author is simulating a ring oscillator as well. If you want to skip to the part discussing initial conditions, just search the page for "initial" and you'll find it immediately.

Hope this helps.
Click to expand...

Thanks a lot it really helped.:grin:
 

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