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Date: Sat, 28 Jan 2012 21:23:57 -0500 (GMT-05:00)
From: daledouglas AT mindspring DOT com
To: geda-user AT delorie DOT com
Subject: [geda-user] nspice analog ic flow: how to size FETs?
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Reply-To: geda-user AT delorie DOT com

Hi all,

When designing in CMOS IC processes, you spend a lot of time sizing mosfets (setting W,L for a given Ids) and cascode gate voltages in order to get the desired operating points. In Cadence, you can DC annotate schematics with Vth, Vds, Vdssat, Gm, etc., and so this is pretty easy. On the other hand, I can't figure out any easy way to do this in ngspice. In other flavors of SPICE (such as Silvaco), an .op is distinct from a single point .dc in that an .op details the operating points (Vgs-Vth, Vds, gm, Ic, operating region, etc., etc.) of every active device. It would be great if this was integrated into ngspice. 

Otherwise, can anyone suggest an easy way to size in an ngspice flow?

Many thanks,
Dale