[sdiy] LTSpice macromodell help

[Dave Manley]

Could this be done with a pair of voltage controlled switches (VCSW)?
I've seen them in the library but haven't used them.


On 4/14/2011 7:03 AM, Harry Bissell wrote:
> I'm trying to make a perfect comparator. So I have a voltage-controlled voltage source
> with a gain of 1e6, followed by a clamp.  The diodes and voltage sources didn't work too well,
> the currents become astronomical. The diode thing works real well at ot near the supply rails, though.
>
> Thanks for the article, its a good read.
>
> H^) harry
>
>
>
> ----- Original Message -----
> From: Tim Stinchcombe<tim102 at tstinchcombe.freeserve.co.uk>
> To: 'Harry Bissell'<harrybissell at wowway.com>, 'synthdiy'<synth-diy at dropmix.xs4all.nl>
> Sent: Wed, 13 Apr 2011 17:32:05 -0400 (EDT)
> Subject: RE: [sdiy] LTSpice macromodell help
>
> Darn! Seconds after I hit the 'send' button I re-read your message and
> realized that article probably _doesn't_ do what you were asking!
>
> So, I pulled Connelly&  Choi off the shelf, and sure enough they use the
> diodes+voltage sources method in their op amp macromodel, using a very ideal
> diode model:
>
> .model dx d (n=.001)
>
> and then diodes using 'dx' to clamp to the positive and negative rail
> respectively. (Hopefully this makes sense this time...).
>
> Tim
> __________________________________________________________
> Tim Stinchcombe
>
> Cheltenham, Glos, UK
> email: tim102 at tstinchcombe.freeserve.co.uk
> www.timstinchcombe.co.uk
>
>
>> -----Original Message-----
>> From: Tim Stinchcombe [mailto:tim102 at tstinchcombe.freeserve.co.uk]
>> Sent: 13 April 2011 22:22
>> To: 'Harry Bissell'; 'synthdiy'
>> Subject: RE: [sdiy] LTSpice macromodell help
>>
>>
>> As well as tanh already suggested, I think the 'arctan'
>> expression used in this nice little article does the job
>> tolerably well too:
>>
>> <http://www.edn.com/article/493732-Modular_macromodeling_techn
> iques_for_Spice_simulators.php>
>
> PDF version:
>
> http://www.edn.com/contents/images/198891.pdf
>
> Tim
> __________________________________________________________
> Tim Stinchcombe
>
> Cheltenham, Glos, UK
> email: tim102 at tstinchcombe.freeserve.co.uk
> www.timstinchcombe.co.uk
>
>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of
>> Harry Bissell
>> Sent: 13 April 2011 16:48
>> To: synthdiy
>> Subject: [sdiy] LTSpice macromodell help
>>
>>
>>
>> Hi all... yes its synth-related
>>
>> I'm trying to come up with a macromodel of a voltage limiter
>> circuit. Electronic Workbench includes such a device, LTspice
>> does not.
>>
>> The object would be to limit input voltages to a range
>> between Vpos and Vneg that I would set. Using a series
>> resistor, two diodes, and two voltage sources is a crude way
>> to do it. I'm looking for something much more elegant.
>>
>> Any takers ???
>>
>> H^) harry
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>>
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