LTspice subckt model for AD734

Hi Helmut,

Thanks for a clean hierarchical schematic!

Amusing myself with how to make a full behavioral model...

Do you have any ideas on how to characterize a CMOS inverter?

I think you could characterize an inverter as an input capacitance versus input voltage and the output as a resistance variable with input voltage and also with a capacitance likewise related. ...Jim Thompson

One usually uses input transition rate and output load as parameters to characterize the behavior of an inverter (or any other gate) ie you make tables of delays which give you output delay and transition given input transition and output load (usually only in terms of capacitance) for a specific corner of pvt.

I'm interested in making a voltage-controlled resistor which matches that of a CMOS transistor. I'm guessing a SINH function might be a good start.

That'll be the easy part. The hard part will be getting input and output capacitances as a function of input AND output voltages.

Tables won't improve simulation time that much. Though they certainly can model parts that are difficult to fit with _smooth_ equations. Take a look at the varicap models on my website. ...Jim Thompson

"Jim Thompson" schrieb im Newsbeitrag news: snipped-for-privacy@4ax.com...

Hello Jim,

I haven't needed the CD4046 for myelf. I guess somebody asked for it. My goal has been to use the highest possible level of components to get it quickly done. Thus I tried to avoid the transistor level as much as possible.

Best regards, Helmut

Hi Helmut,

I wasn't thinking transistor-level, just a behavioral equivalent that avoided special digital structures... make an inverter from G-sources and a capacitor or two.

That led me to thinking that an NMOS device is just a two-variable G-source (VGS and VDS) with a TANH equation...

Then one could make up their own accurate digital library using analog behavioral components :-) ...Jim Thompson

Helmut, do you have any idea why the LTSpice group might "forget" members? It shows up under "My Groups" but then a screen pops up to "Join Now". Weird.

Any chance this group might be newsserver accessible some day? Most technical ones already are, via gmane. The Yahoo interface is IMHO a pain, inefficient and very slow.

Subscribe to the E-mailed "digests". I do. I go thru the Yahoo interface so rarely I have trouble remembering my password ;-)

Of course I still predominately use PSpice, but the group is just stock-full of great ideas, and pro-level posters... Helmut and Woodgate... yep _our_ Woodgate. ...Jim Thompson

Can you post via that?

Yes, that is very true. The icing on the cake would be if Mike Engelhardt would stick his head in there once in a while.

I think so. I've certainly "Replied to group" with suggestions of solutions to problems.

I've not seen Mike post there. That doesn't mean he hasn't. ...Jim Thompson

That would be cool. But first I have to find out why it won't let me in anymore, else I won't be able to set anything.

schrieb

Too many PHTTTTTTTTTTTTs.

schrieb

Helmut is (I think) the moderator... ask him. ...Jim Thompson

Hello Joerg,

"Join now" only menas you have to login with your password. This happens after a every few weeks for safety reason. Somebody from Yahoo had this bad idea to name this "Join now" instead of "Login".

Type in your login and password. In the next window, directly go to Messages.

Best regards, Helmut

"Jim Thompson" schrieb im Newsbeitrag news: snipped-for-privacy@4ax.com...

Hello Jim,

A simulation with digital devices is much faster than the same with analog devices.

Best regards, Helmut

Thanks, Helmut, but it doesn't work anymore. After entering name and password a 2nd time it pops over to regular Yahoo. Wants all that a 3rd time but won't take it. Plus it moans and groans about cookies before that and then sets ad cookies.

IMHO they have royally screwed up this time. Can't you open the LTSpice group to gmane like the other tech groups? Then all this script kiddie nonsense is gone and people can use it like a real newsgroup. Without the file section, of course, for that one would have to wade through the morass (or try ...).

Of course, but how many people have, or can cope with, digital primitives ?:-)

And TANH is determinate... not exactly an analog component. ...Jim Thompson

I've tried to register several times. Each time it's failed with various messages about cookies (enabled) Javascript (enabled), or just plain not responding. Eventually, I gave up. A plague on its house!

BTW have you noticed the fine print? "Yahoo collects personal data".

The only thing true I feed such sites is an E-mail address. And that's not a problem, I currently have 260 different E-mail addresses :-) Anyone who abuses an E-mail address... it's gone. ...Jim Thompson

Now you know the reason why I declined the "upgrade" to Yahoo mail from SBC or now AT&T, which at least to me looks like a cheap outsourcing attempt.