RF circuit design.

[snip]

Sure, there are a handful of ways of having some resistors and capacitors around the transistor. Since they are just a click away, why not check them all ?

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Yes.

I recently did a successful design at 2.2GHz, and have done one at

3.8GHz that needed only a mild amount of tweaking... predicting spiral inductors is black art ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Hello Rob,

Just my two cents: Place the emphasis on designing and building. Simulations are nice but their value is often inversely proportional to the frequency. At a GHz or so parasitic component values can render a SPICE simulation useless. Except when designing chips, but that's a whole other topic.

Regards, Joerg

These were supposed to "talk" (coupled), but the foundry's numbers were off.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
     It\'s what you learn, after you know it all, that counts.

Hello Jim,

That holds true not just for the spiral ones. The real challenge is to predict how much they'll talk to each other.

Regards, Joerg

Hello Jim,

Hopefully they'll at least swallow the cost for that run.

Regards, Joerg

They had to, I was designing for them ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | It's what you learn, after you know it all, that counts.

I've never subscribed to this philosophy. If you are designing for

1GHz, then you need a HUGE investment in signal generators, spectrum analysers and network analysers. Whatever the potential pitfalls of inaccurate spice models and insufficient modelling of the parasitics, there are just as many pitfalls with the hands-on approach; you end up measuring the noise-floor of your analyser, unexpected harmonics are just down to the the IP2 of your analyser's front-end, you screwed up the two-port cal of your VNA, etc.

Conversly, one of the wonders of simulating is that you can very easily determine the effect (or otherwise) of lead-inductance, parasitic capacitance, etc. on your design's performance. You've only got to look at the literature to realise that, if you're careful, simulation can agree very well with measurement, and the advantage of simulating first is that it gives you some expectation of the performance of your real circuit that you otherwise wouldn't have.

--
Rick

Hello Rick,

Usually one of the virtues of someone who learned by building hardware very early on is that he or she is able to make do with a surprisingly limited assortment of gear. There have been many cases where clients were chasing a problem with a $50,000 analyzer and I finally found the root cause using a borrowed Radio Shack scanner. Doesn't always work, of course, but many times it does. You just have to know when it won't and why.

Agree, I did find stuff like reverse recovery spike via SPICE that one couldn't see on the available oscilloscopes. But it's also easy to be fooled by simulators. Same here, one has to know where the practical limits are.

Regards, Joerg

Hi at all. Thanks for all the replies. I assume from the replies is that I can use the simulator to model accurately (within reason) circuit that I design. I am more interested in getting the theoretical circuit correct at this moment.If my circuit calculations are correct I will be able to see it in the simulation.(By the way I'll be using SWCAD for simulation purpose) Cheers for now Rob