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is there any free but good/decent/usable schematic editor for analog IC design?

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alex2013

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Hi,
For quite some time I've been searching for a free but good enough schematic editor for analog IC design. What I found were usually for pcb design with discrete components (like LT Spice for example).

Can anyone share what kind of free but good schematic editor they use or know?

Thanks.
 

Well, if you really plan to take it all the way to round-n-shiny
then you need more than schematic editing, you need things
like at minimum a SPICE netlist export (preferably an integrated
layout and verification tool - SPICE:SPICE LVS can give you a
thumbs up / thumbs down but is not too debug-friendly).

The LASI system is kinda cute, has schematic, layout, SPICE
export from either, DRC, etc. There are some MOSIS processes
supported, perhaps they have added new ones since I last
looked.

Electric is another good suite, it's not useful to me because
my needs often involve GDS-II import and the data structure
of Electric uses constructs that can't be made from GDS-II,
only the "forward path" of direct layout editing. But a fairly
complete tool as long as you're working entirely within it.
You will have to compile it yourself if you don't want to pay
for object-code on media, source is free.

Several open-source schematic editors with SPICE export.
Where you'd get the models and device library, is a problem.
I'd look into gEDA and the side branch links you may find.

Silvaco and Tanner are tools you'd pay for but are on the
affordable end and have some decent level of foundry
support (PDKs).

I know old-timers who still design ICs using antique PC
based tools, and work with foundries that still let you
tape-in against a groundrule package rather than insisting
on a Cadence PDK verification. These are getting fewer....

Teh Googlez probably would cough up a few million hits
for "free CAD schematic", if you have time to kill. There
are sites that try to keep track but staleness can be a
bit annoying.
 

free but good enough schematic editor for analog IC design

Take a look at Falstad's animated interactive simulator:

www.falstad.com/circuit

It supports several common analog IC's, including op amps, 555 timer, 4017 decade counter.

Also a variety of logic gates and flip flops.

You can choose white or black background.

You can add text labels anywhere, at any size.

It cannot export a schematic in image format. To get a schematic, you have to grab a screenshot.
 

I don't think Falstad will be much use doing IC design. As Dick suggested, LASI is probably one of the few (only?) free ones. I have used it for layout but I must admit to using a commercial Spice package for simulation.

Keith
 

I like Qucs from SourceForge.
It includes a nice schematic editor, verilog support, SPICE netlister, and a decent SPICE simulator together with (modest) presentation tools for the results.
 

I don't think Falstad will be much use doing IC design...

Perhaps not. I wasn't sure what features the OP wants in a schematic editor, to make it suitable for IC design.

Even though it has limitations, I find it has a number of conveniences.

Earlier this year Falstad's simulator enabled me to assist a professional engineer in his design work. I received financial compensation.

Falstad's is easy to use. It creates schematics which are straightforward and uncluttered. Components have a single spec displayed beside them.

You can place/ move/ delete components easily, even while the simulation is running. Results update immediately.

The animated simulator portrays amounts of current flow through wires. Scope probes can be put on any component. Scope traces can show voltage, current, watts, V/I, and lissajous figures.

I wonder if this will demonstrate something about Falstad's suitability for IC design? Here are the internals of a 741 op amp (included in the library of circuits). The scope traces travel across the same screen below the schematic.

 

Unless it supports BSIM 3 and BSIM 4 models then it will be no use for IC design. Also, netlist export for LVS is a requirement as is AC analysis.

LTspice is workable for bipolar IC design I believe but I don't think it includes the necessary BSIM models for CMOS IC design.

Keith
 

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