Originally posted by nenadilic84
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Thanks for your video link, nice build on your window motor setup.
Now that I use my home computer I managed to see your uploaded schematics on the astabil variable frequency/duty cycle multivibrator (in my office computer I see only a small rectangular icon instead of the schematics picture). And I think it is ok, it should work and be adjustable as you describe, no problem with that, using two timers from the NE558 quad package. Now I am certain that this circuit you show in that scematics can surely be built from either two LMC555CNs or a dual CMOS timer like TLC556Cs. Of course, the normal NE556 dual timer would also be good. However, I am not sure your claim on the 100MHz operation... Suppose you use 100 Ohm and 100pF for R1 and C1, they give 10nsec half period, and if R2 and C2 are also 100 Ohm and 100pF, then the other half period is also 10nsec, this could give a 20nsec total which sounds like 50MHz indeed BUT as far as I know the bipolar IC manufacturing process the NE555-558 timer family was fabricated in the 70s and 80s, they cannot work as fast as that. This is why I wrote I doubted that.
But nevermind, in this push-pull multivibrator circuit possibly even a few MHz operation is surely possible with the CMOS higher speed timer versions, so they would be worth trying.
Do you happen to have an oscilloscope or a frequency meter? I would like to know if you reduce R1, R2, C1 and C2 to small values like some hundred Ohms and some hundred picoFarads, then what frequency can come out from your NE558? The scope would be best to see the waveform of course....
Thanks, Gyula
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