As a first step, can't you try to generate waveform plots with readable axes in Multisim. This would allow to discuss the results. Up to now, I can't say but "looks wrong, somehow".
If I understand right, you are showing the same waveform for transistor and 741 circuit. :-(
Sorry I ahave managed to over write one of those images below so now it doesn't match the text. The image showing the noise is of a pretty stock standard transistor multivibrator that you would use in an LED flasher. But in multisim at least they never seem to give a real tidy and clean signal.
Just for fun I am trying to implement a voltage boost circuit to take 12V to 18V.
Given the trouble I was having with the 'noisy' transistor multivibrators I hunted around a bit more and found this fully designed booster circuit that includes regulation:
Here is is in multism:
I have swapped the transistors used by the author to others I have on hand and it seems to still work very well.
I also changed up the zenner diode to get the output voltage to 18V under load and this has worked well also as you can see.
But I am a little puzzled by the circuit. There must be a multivibrator in order to drive the inductor and it has to be around the two BC337's. But it doesn't look anthing like the nice symetrical transistor multivibrators I have been playing around with previously in multsim. Can some one explain the multivibrator part of the circuit to me?
The author has used a pretty heavy duty transistor on the inductor. Since I wouldn't be drawing large currents from this thing I assume I can get away with a far less heavy duty transistor.
Interesting........ If I reverse the battery the circuit still functions but I only get -100mV out. But if I can figure out which components need to also be reversed it looks as though it will function nicely as a negative voltage booster as well.
That noise should not be there. Try reducing your maximum time step in multisim.
I assume you mean the time base scale Jason. I have fiddled with that a bit but it doesn't seem to make any difference - I still get noise.
Is that noise and artifact of multisim or is it likely to occur in a real circuit?