40106 VCO revisited...through zero capabilities?

synthmonger

I'm not 100% sure this could be considered a 'Through Zero VCO' as I've never built one before, but I can say that it goes through zero.

You can leave out the sync sections just be sure to ground the input pins. You can also leave out the buffered "square out" section. The triangle output buffer and level shifter is a must. The triangle output will look a little "Aliased" from the high frequency VCO clocking the switch.

You can also use this as a "through zero" voltage controlled resistor. Just use the in/out pins on the 4016 switch as the ends to a resistor. I've used them in Phase Shifter, EG's, other VCO's and a buncha other designs with positive results.

Anyone wanna give it a shot and post feedback? Cool

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DGTom · Posted: Tue Oct 06, 2009 12:08 am Post subject:

very interesting, I might give this a shot tomorrow (sans "sync" & square) if I can overcome the brain-fart I've been having transferring this 4069 VC "tube boost" from bread to strip-board.

The VC Resistor application seems like it might come in handy as well! Idea

In use whats the differance, if any, between the 2 "sync" inputs?

Thanks very much for posting Very Happy

synthmonger · Posted: Tue Oct 06, 2009 3:16 am Post subject:

There really isn't any difference between the two sync inputs. I was thinking of turning the sync sections into "Pulse Width Modulators" that can vary the sync width. I would use them for PWM on either output waveforms (it accepts any wave not just tri/saw/sine) but I can only get a reliable 1-50% width not 1-90% like I could with op-amps. It is possible to get 1-90% PWM with three but as the frequency changes so does the duty cycle. I haven't figured out how to get around that yet.

synthmonger · Posted: Tue Oct 06, 2009 3:17 am Post subject:

You should check out my 40106 VCO in the Lunetta thread for an exponential current source. It may work better than the thru-zero vco method I mentioned.

DGTom · Posted: Tue Oct 06, 2009 8:04 pm Post subject:

your 40106 VCO is great, used it quite a few times, mostly as a high freq. core driving a divider, 4018 / 4024 etc.

expo or V/Oct. isn't really a concern for me, I like the idea of thru-zero"ish" CMOS tho Very Happy