[SI-LIST] Re: Negative Resistance of Crystal Oscillators

Hi Merrick,
 Thanks for the answer. I have few more doubts which I
hope you can clear. 
 The negative resistance is due to crystal oscillator.
If so why do I need to replace crystal with current
source.
 How will oscillations occur and also different
impedance as crystal offers at different frequencies
when I replace crystal with current source?
  I am modelling crystal as a parallel resonant
circuit in Hspice.

Thanks in advance,

Regards,
Partha!

--- "Moeller, Merrick" <mmoeller@xxxxxxxxxxxxxxx>
wrote:
> Hi,
>       Place a unit current source in place of your 
> crystal, Include a parallel cap to account for Co.
> Wideband AC simulation. Plot Real[Z],you should see
> Neg R at your
> frequency of intrest. If you are working with 3rd OT
> you will see a crossing point prior to your
> frequency.
> 
> Hope that helps. If you have any questions I should
> be
> able to help.
> 
> Merrick M. Moeller
> 
> 
> -----Original Message-----
> From: Parthasarathy Sampath
> [mailto:parthsv@xxxxxxxxx]
> Sent: Tuesday, May 20, 2003 2:48 PM
> To: si-list@xxxxxxxxxxxxx
> Cc: analogcmos_vlsi@xxxxxxxxxxxxxxx
> Subject: [SI-LIST] Negative Resistance of Crystal
> Oscillators
> 
> 
> 
> Hi all,
>   I need to make certain measurements on crystal
> oscillator ckt. The closed loop has a crystal
> oscillator with Invertor as feedback to provide 360
> deg phase shift.
>    One measurement is to measure Negative resistance
> in open loop simulation.
>   Is it possible to measure negative resistance of
> the
> oscillator in open loop. If so how will I have to
> proceed?
> 
> Thanks in advance
> 
> Regards,
> Partha!
> 
> 
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