M-SimonI was discussing my ECN article Some Tools I Use with the guys on the TinyCAD list and they suggested that I look into FreePCB for PCB layout. I did and it looks like a wonderful tool (I have just downloaded it and haven't had a chance to use it yet). What really caught my attention is a page of independently developed add ons which include an auto router and software that creates very photo-realistic images of the top and bottom of a PCB (part of this sentence was lifted directly from the FreePCB site). You access all these wonderful downloads by going to the Download page of the FreePCB site. And of course FreePCB integrates with TinyCAD.

Another tool I have been using is 5Spice. It has a truly easy to use interface for the schematic draw part of Spice. In about an hour of noodling around I was up and simulating. And that is not the only good part of the user interface. The help files are most excellent. There was a model missing from the library I wanted to use (2N7000) and I was wondering how to add it. No problem. A consultation with the help files showed how to make the small changes necessary to get Windows to accept the new files (you have to change a file extension from .txt to .mod to get the file recognized by 5Spice). The really great thing is that the model files loaded exactly as provided by the manufacturer (On Semiconductor). No modification of the files required. 5Spice has a whole page devoted to downloadable models. For another circuit I was working on the developer of this wonderful product, Richard Andresen, suggested that I use a more modern JFET such as the 2N4416 vice the part I was working with in physical reality the MPF102.

The 5Spice software is useable free for 30 days (in a somewhat truncated version) and then you have to buy a license (under $200) to use the whole thing (basically larger schematic pages). If you like to do simulations to get a feel for the design space preparatory to doing prototyping (you can't beat the real world - don't even try) this is, in my opinion, the tool to use.