Post-Sim of OP amp problem!!!

[shaq]

Dear all,

I have a problem.

When I do the post-sim by using hspice, I get a lot of the warning messages.
I just pick the one of these messages.

 **warning**  no dc path to ground from node        1:noxref_2641      defined in subckt opamp           
small conductance is inserted by setting dcstep=1

I'm so confused because the DRC&LVS of op amp is PASS!!!

What command of hspice should I use?

Plz help me!!!

Thanks so much!!!

 

[vbhupendra]

did u got warning in lvs about pStamperror or something like that.

 

[paulux]

It may be due to the problem of non-convergence model. Set your LVS extraction without Ccoupling to run simulation.

 

[borislee]

Check the node of 1:noxref_2641. It is not difficult to confirm whether there is dc path to ground from this node.

Comparing to pre-sim, there are many more parasitic capacitors in netlist. It is also common that some new nodes appear and may be floating.

 

[maxwellequ]

You must have some metal lines floating on the layout. This is ignored in LVS.
Either you find and eliminate it, or go to the netlist and place a large resistor (for example 1e12 ohm) from every floating node to gnd.

Rgds

 

[flamingo]

I don't think this is a serious problem. With DCSTEP and GMINDC option the simulator can give correct results, and similar problem also happened during schematic pre-simulation.