"Leon Heller" wrote in message
...
"Paul Keinanen" wrote in message
...
On Sun, 06 Jun 2004 17:59:00 -0500, Ed Bailen wrote:

The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Typically, an oscillator is just a noise amplifier with some frequency
selective feedback. ...

If the simulator does not simulate the thermal noise

I do not believe this is necessary. The normal charge-up of any coupling
caps will get you "off center" at the start. On PSpice ver 9 one of my
students "couldn't get an oscillator to go". I lenghtend the simulation
time and found that it took longer than he had set for the transient
analysis.
Out of the box on PSpice I got both a 555 and Colpitts to fly. I can't
speak to CircuitMaker, but there may be analysis set-up parameters such as
the aforementioned initial condition which may be the key. PSpice also has
something about "skipping" an initial transient state/solution which I
haven't experimented with to comment further, but could be a consideration.
Watch the options...

--
Steve N, K,9;d, c. i My email has no u's.