ECL logic SPICE models

and

boost

IBIS

Some of the cheapest gain-bandwidth around is in darlington MMICS. You can get 4-8 GHz of stable, 20 dB-ish gain for under a buck. They work fine in pulse apps, too.

John

One issue I found with RF devices was that you can sometimes only obtain small signal simulator models that aren't very helpful with pulse apps, plus require software that costs more than your Volkswagen. Even with big LDMOS parts I had that happen. One company (PolyFet) stuck out and provided SPICE models. So the big competitor will be left out ... sorry, NXP.

There are tons, like

Some of the SOT-89 devices are really interesting.

I don't simulate this stuff, I test. Most microwave parts are characterized small-signal, S-params. Spice models are very rare in this business. I know things about some of these parts that the manufacturers don't know.

John

Those are cool. However, the ECG003 is over three bucks although the datasheet looks great.

Lately I have simulated more, and then straight to layout. The one that's in fab right now is a white-knuckle ride because I am using a device in a weird way. Usually pans out though.

What often amazes me is how close to abs max people (and sometimes app notes) bias RF devices. When it says 7V they bias them to 5V or 6V on the collector/drain. Some day a huge pulse finds its way into the input, almost saturates the device, then it lets go, the inductor shoots up ... phut.

I've run 7-volt-rated MESfets at 18 volts, and 2 volt RF schottkies at

1. I sometimes test parts to destruction and then back off some. The performance is often worth the small risk.

Lots of RF devices seem to have voltage ratings that assume an RF tank in the output, so that the actual instantaneous drain excursion is 0 to twice Vcc. The RF guys are really, really terrible when it comes to realtime specs. You're lucky to get any DC curves. More often there's an app circuit with an input match, an output match, and a gate bias trimpot.

John

Really? I thought that went away with vacuum tubes!

Tim

I've seen that. But if you are a consultant and this goes into some aircraft you can't design like that. Even with an indemnification clause that can cause lots of grief should it go wrong in only one case. It's got to be by the book.

All they really offer in many cases is a set of S-parameters. Since I design a lot of pulse circuitry I almost do a rain dance every time there is just a snippet of SPICE data.

Somewhere in my bag-o-tricks is an S-Parameter-to-Spice-Model converter (and vice-versa).

When I find it I'll post.

...Jim Thompson

All my S-Parameter to Spice stuff has been updated on the SED page of my website... except a good article by Microcap... get that from their website, so I don't step on any copyright toes ;-)

...Jim Thompson

That would be very kind.

However, except for super large transmitter devices (and sometimes even then) the S-parameters have been measured under small signal conditions. Doesn't help much when pulsing them hard, then you are back to what John said, experiments on the lab bench. Got one of those coming up. I am going to do the first run with tubes again to see if the concept pans out, in order not to have stuff blow up in my face. It's really nice to know that one can still buy the mil version of the 6146 tube, at affordable prices. So far I haven't blown one though, only tired out a pair.

Thanks. I assume you mean this link:

Now I have to learn QuickBasic, whatever that is ;-)

obtain

sorry,

There are four articles there, each beginning (in the listing), "S-Param...", all of which are elucidating.

...Jim Thompson

obtain

apps,

sorry,

Unless I understand something wrong the first three are for extracting S-parameters from SPICE or PROBE (Orcad's version of SPICE).

But maybe I'll read them again and some more elucidation will come :-)

obtain

apps,

and

sorry,

input,

...

Most math is bilateral ;-)

...Jim Thompson

obtain

apps,

with

and

sorry,

input,

...

Ok, true, I was lazy here. Thought about some SW-routine where you slap the datasheet on a scanner, press magic button, out comes SPICE sub-circuit :-)))

obtain

apps,

with

and

sorry,

app

input,

...

clause

I can do that for you... for a fee ;-)

...Jim Thompson

I know :-)

Right now I don't need to convert though because I just went over to manufacturers who furnish SPICE models. But if we really need to and it's crunch time I might take you up on that, or a client of mine would.

If you and your son-in-law (the computer guy) get together and write a program that does this you could probably sell it to numerous manufacturers. Every time a guy like me walks away because they don't have SPICE models that means serious money is being left on the table. Once the BOM is done and done, it takes a major earth-shattering event to change it. Or very painful price cuts. I had sales reps almost in tears when they realized they shoulda ...

The RF boys call that "load pull" testing. People make interfaced load-pull boxes so you can automate exploring the nonlinear space of large-signal RF amps. Between explosions, anyhow.

google "load pull tuner"

Got one of those coming up. I am

My first job interview, I told the guy that I preferred tubes to transistors because tubes were harder to blow up. The smug SOB said "that won't do" and sent me away. My next interview, I said the same thing, and Melvin laughed and hired me. I designed $200 million worth of stuff for him.

John

obtain

sorry,

Mostly I just press on, eye-ball the rough L and C values, go into the garage and see if I have enough suitable variable capacitor for a test. Then it's off to the plumber's place for some copper tubing, to make the coils. At Home Depot that's now called "plomeria".

I've had a similar event with a potential client a long time ago. Proposed an unorthodox solution that seemed to be "too simple" for them, not academic enough. They turned me down. A few years later this company was at the financial end of the rope and went belly up. The sad thing is that my solution would have potentially saved them, along with about two dozen jobs :-(