sawtooth circuit modeling?

Thats easy. Doing a sine wave oscillator with an LM555 is a bit harder.

On the CMOS LM555, the pin 3 swings all the way to either rail. A couple of resistors with diodes in series can make any rise vs fall ration within reason.

The classic sawtooth osc used a neon lamp or as I vaguely remember some kind of diode.

A high voltage one used the 0Z4 if you know what that was.

You're at a total loss? Of course we'd all like a program that would convert our randomly plunked-down "circuit" into a set of relevant equations, but such a beast does not exist. If someone were to write a program that would attempt to recognize common circuits and supply all the relevant preprogrammed formulas. That'd be nice, but it would quickly be seen as a mere toy, only able to handle a limited set of pre-programmed circuits. Even for those, it'd probably fail to provide a critical piece of information that one had in mind for his exact application.

As a teacher, a better approach would be to teach your students how to derive the formulas themselves, and how to estimate or calculate the circuit results. Or you could have them run some spice simulations and compare some measured results from spice against their calculations. ON Semiconductor used to offer the demo version of Intusoft's spice on free CDs, which you could order and hand out to your students. You can ask, but I think now they only offer downloads, but they're pretty big files,

this is not a course in circuits, it's a course in using computers to address biological problems. most of the students in the biological sciences at my university have zero experience with MATLAB, Mathematica, IDL, Perl, or any of the other tools that physicists and engineers use to solve problems. what i was hoping for is a set of differential equations that the kids would have to numerically solve using one of those common computational tools. the circuit would simply be a simple projection of the complex underlying genetic network, something to sort of 'motivate' the problem.

dan