sawtooth circuit modeling?

[Jasen]

the data's not published just yet, so i'm reluctant to give out too
many details.

it looks like you using an op-amp integrator might do the trick for
the ramping-up, and if i can rig up a switch across the capacitor that
will quickly discharge it once the voltage has reached a certain
value, then i've got my sawtooth. so now i guess the question is: how
do i implement that switch? it's been so long since i've looked at an
electronics textbook; at least 10 years. is there a way to set up
some kind of comparator, so that when the voltage on the output of the
op-amp reaches a certain threshold, the switch is thrown and the
capacitor rapidly discharges, and then is quickly thrown again so the
ramping-up can begin all over again?

depending on the voltage and current involved you could thyistor with a
zener to set the trigger level, the ne32 neon lamp, or just a spark gap,

Bye.
Jasen

 

[MooseFET]

Yes it is. It has more parts that yours but then again, it probably
works! I like the op-amp design because it is more symmetrical. Can
you use the 555 version to make a nice triangle or reverse sawtooth?

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.

 

[Bret Ludwig]

depending on the voltage and current involved you could thyistor with a
zener to set the trigger level, the ne32 neon lamp, or just a spark gap,

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.

 

[Winfield]

i'd like to model a circuit that outputs a sawtooth function. there's
really two things that i'm looking for: 1) a schematic of the simplest
circuit that can produce a sawtooth output, and 2) a way to model it
with something like MATLAB or Mathematica. is anyone here familiar
with any schematic capture circuit analysis packages, particularly
ones that can generate the underlying circuit equations? what i
imagine would be ideal is if i could just plunk together a couple of
resistors, capacitors, and op-amps in a SPICE like program, then get
the equations that describe the circuit, and finally carry those
equations over to MATLAB to model how things change as i vary system
parameters. i'm at a total loss here. does anyone have any
suggestions??

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,
https://www.onsemi.com/PowerSolutions/myon/intusoft.do Or get
all the files from Intusoft, http://www.intusoft.com/demos.htm

 

[dantimatter]

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

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

 

[John Fields]

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.