RE: ac analysis to ibs model

Wenqing,

The input and enable nodes of the B-element is purely for control,
and these are digital, i.e. an analog signal applied to them will
result only in a logic "1" or "0" on the output. You should not
view the B-element as if it was an op-amp. You cannot do an AC
analysis stimulating the input and look at the response at the
output. This simply does not make sense with the B-element (or
for any digital buffer for that matter).

You can only look at the B-element as a one-port (I/O node to GND,
or I/O node to power) and look into it at its analog side, the
I/O node. If you did that, you should see the complex impedance
that is composed from the IV curve and C_comp values.

Arpad
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-----Original Message-----
From: Wenqing Zhang [mailto:wqzhang@avanticorp.com]
Sent: Wednesday, March 28, 2001 6:38 PM
To: ibis-users@vhdl.org
Subject: ac analysi to ibs model

hi, all,
firstly, thanks for your reply and help to my yesterday's question.
now my question is the following:
I ran a AC analysis to a "output" buffer with Star-Hspice, but
simulation results of the ouput termination of that out buffer were zero.
I think the reasons are the following:
     AC source is in the input terminal of that output buffer, but the
     input part has no electrical relation with pullup circuit, pulldown
circuit,
     power clamp circuit, ground clamp circuit in frequency domain.
     this will lead to that PU, PD, PC, GC circuit have no AC source, so
     the output of that out buffer is zero in AC frequency analysis.
in fact We did a AC analysis to a "input" buffer with Star-Hspice,
simulation results also were zero.
I think we can't do ac analysis to ibs model version3.2.
Perhaps AC source should not be placed in the input terminal of buffer.
where should we place ac source?
perhaps we should increase four frequency response curve in ibs model.
that is corresponding to PU, PD, PC, GC circuit.
How do you think about it?
thanks for your help.
I am not a member of ibis-user, so pls email to:
wqzhang@avanticorp.com
how can I become a member of this group? who teach me?
best regards,
wenqing
  
  
  

-- 
Thanks
Wenqing Zhang
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