Spectre Warning -- No dc path from node to ground

I'm trying to simulate a circuit in Spectre. I having a warning which
says " No dc path from node ... to ground. Gmin installed to
provide....". I have a 1pF capacitor at the output. Am I missing
something.??

Also, is there a way to perform analysis using Spectre ?

Thanks!!

 

Hi Vignesh,

Q1: If your node is connected to an ideal capacitor only, then this
node would be floating during the DC analysis as a capacitor accounts
for an open in DC. So to avoid this situation, Spectre inserts a 'big'
resistor (R=1e12 Ohm) between this node and the ground. Well actually
Spectre inserts the conductance gmin whose default value is 1p, that's
why I talked about a resistor of 1e12 Ohm earlier. This is a normal
warning and there is nothing to worry about. You won't see this
problem if your node is connected to a real capacitor. Real capacitor
do a have a finite serial resistance.

BTW, These are few notes from the Spectre User Manual, I have provided
the path to this manual in previous post.
Chapter 14: "Identifying Problems and Troubleshooting" -> Section
"Spectre Warning Messages" -> Topology Messages

"Notice from spectre during topology check.
Only one connection to the following node: 4
No DC path from node `4' to ground, Gmin installed to provide path.
The Spectre topology checker identifies floating nodes and
automatically inserts a gmin
resistor (1e12 Ohms) to prevent a non-isolated solution. The Spectre
simulator then displays
a message telling you what it did."

Q2: I don't quite understand what do you mean by :
"is there a way to perform analysis using Spectre ?"
Spectre is capable of DC, AC, Tran, Noise, S-Parameters ... analysis.
Loads of them really. Just give a look at the Spectre Manual.

Hope this help.
Riad.

 

Oops!! I meant " Power Analysis".
And thanks for the capacitor info!!. I was picky about it b'coz I
assumed that it could be something serious.
Anyways, thanks a bunch.

Vignesh