Behavior transistor models?

"RobertMacy"  wrote in message news:op.xm2o7w2c2cx0wh@ajm...

On Wed, 01 Oct 2014 13:13:28 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

>> ...snip....
> If it says...
>
> .MODEL ModelName NPN(...
>
>> it's conventional BJT, and BJT parameters have been fitted to the
>> datasheet
>
>> If it says...
>
>> .SUBCKT ModelName Node(s) [PARAMS: ...]
>
>> it's behavioral
>
>                                         ...Jim Thompson


>Oh, I always called them models [even if they're a subckt] and behavioural 
>[because the subckt is based upon observation, not basic principles]

It gets into a grey area as, for example, there are parameters in standard 
spice models that are there empirically, not because of a 3D physics based 
analysis.

>For example, I always thought behavioural was made up of a conglomeration 
>of mathematical components that 'acted' like the component. not based upon 
>basic, deep down principles of a particular mask set using a semiconductor 
>process.

Probably a bit of individual preferences for the name "behavioural". For me 
I agree with what you say. I usually only refer to "behavioural" as 
mathematical expressions and ideal components. However, in Spice this will 
always be achieved by putting the description in a .subcuit. If one then 
makes say, a diode by an exp() function, one might end up just using a 
diode, so it morphs into mix of mathematics and Spice parts to make, what is 
still, essentially, a "behavioural" description.

In SuperSpice I actually a set of components, like edged clocked d-types 
using nothing more than tanh()

Kevin Aylward
www.kevinaylward.co.uk
www.anasoft.co.uk - SuperSpice