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Faux MOSFET... Behavioral Modeling

For sometime now I have been trying to build a behavioral model of logic gates that was consistent with real-world behavior when mixed into an Analog environment.

(Existing logic models, such as those in PSpice and LTspice are state machines and do not behave properly when used for Analog applications, such as when you build a crystal oscillator around a 74HCU04.)

So I now invite you to visit the Device Models & Subcircuits page of my website...

and take a look at FauxMOSFET.pdf, where I have finally created a purely mathematical behavioral model of a MOSFET... using, of course, my favorite math function TANH :-)

With all derivatives continuous, it is suitable for modeling logic elements that can be run in an Analog simulator environment.

Watch this space for further announcements as I develop inverters, gates and complex functions that will run on any old analog simulator. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson
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At first I was all "Hyperbolic tangent, WTF does that have to do with SPICE?" Then I saw a TANH plot and the light came on. :) FWIW this guy has an intro to Analog Behavioral Modeling.

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  /  \__/ 
  \__/    Don Kuenz 
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Reply to
Don Kuenz

Thanks, Don, that's a nice intro and a nice composite listing of the different functions available. I've been at this long enough that I know that list by heart ;-)

If your simulator supports VALUE, I'd avoid the POLY form altogether... it's not only obtuse, but difficult to keep your head and the coefficient order on straight for any order above 2 ;-)

I settled on TANH while pursuing how to handle (simulation device) current sources which would pull voltages to infinity if unrestrained. My devices...

will not pull below zero volts, thus not only behave "real world", but have no convergence problems (limiting implemented with a TANH function). ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

I forgot to mention one thing that may be of interest. The transfer function of your everyday bipolar differential pair is TANH. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

That's interesting. I might have thought arctan since the curves look similar, but I haven't done that math.

Reply to
Daniel Pitts

See...

One of my very first patents (filed 1965)...

takes advantage of that transfer function to accomplish harmonic mixing. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

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