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Simulators >> Circuit Simulators >> problem with cccs in analogLib in spectre
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Message started by ethan on Sep 28^th, 2006, 11:51am

Title: problem with cccs in analogLib in spectre
Post by ethan on Sep 28^th, 2006, 11:51am

Hi everybody again,

I have tried to use "cccs" in spectre to build the ideal current amplifier. I am working in schematic in Cadence and doing simulation through Analog Simulation Environment. I have no problem with this.

The problem occurs when I add the ideal current amplifier with other NMOS and PMOS transistors in schematic and do simulation. The spectre always complains that some NMOS and PMOS vgs and vgd are beyond breakdown voltages. I know this is caused by the ideal "cccs". But I don't know how to fix it.

This kind of errors also happened for other ideal sources, like "ccvs", "vccs", "vcvs", etc.

I am wondering whether there is a way to combine ideal "cccs" or "ccvs" sources with real NMOS and PMOS spectre symbols to do simulation and have no such errors, such as vgs or vgd beyond breakdown voltages.

Appreciate your help.

ethan

Title: Re: problem with cccs in analogLib in spectre
Post by Geoffrey_Coram on Sep 29^th, 2006, 3:23am

I'd expect trouble with a cccs and MOS devices, since they have no gate current. A ccvs should be OK. You might want to investigate the min and max parameters for the controlled source, or be sure you have feedback to prevent large inputs from causing trouble.