Comparator [sdiy] inversion, CMOS, etc.

Cynthia Webster cynthia.webster at
Sat Aug 3 17:45:05 CEST 2002

Hi Gavin!

There's an excellent Voltage Controlled Comparator on Ken Stone's
Cat Girl Synth site.  See his Gated Comparator (which is an eight-level
staircase window comparator)  I finished building a prototype of one last
night with a Modcan modular style panel and banana jacks and it works great!
I'm building  a limited edition of twelve of these for other Modcan junkies
like me

There is a picture at the top of the page of my Modcan Style Panel artwork

Hope this gives you some ideas!


> on 8/2/02 1:27 PM, gavin at elmystico at wrote:

> OK, here's a sort of "Grab Bag" message, I've had a lot of ideas lately and
> no budget so things are sort of floating around in this abstract space...
> 1.  I need to invert a logic level pulse from positive to negative.  In
> other words the way the signal is now is 0V-+5V,  I need it to go from
> 0V--5V.  Normally in this application I'd use an OpAmp to invert it BUT this
> is a very High Frequency application and So far the circuitry is all TTL so
> if I can get away with not building an additional bipolar supply to power Op
> Amps I'd like to.  In my understanding a CMOS inverter like the 4049 or a
> TTL inverter like the 7404 will just put the signal 180 degrees out of
> phase.  Or if I need to use an Op Amp has anyone used the 351 for RF type
> frequencies that can vouch for its slew rate at high frequencies?
> 2.  I also need to take a signal oscillating between -5V and +5V and bring
> it up to 0V - +5V while keeping the waveform intact.  A comparator powered
> between GND and +5V will act like a schmitt trigger and a half have
> rectifier will preserve the upper peak but square off the lower.  Will
> mixing in a +5V DC signal through an opamp mixer bring the signal up to 0V -
> +10V?  Then I can reduce it with resistance to the appropriate amplitude.
> 3.  Thinking about pattern generation and analog computers has led me to the
> idea of building a voltage controlled comparator.  A simple circuit, to be
> sure, has anyone seen or implemented something like this?
> Allright that's where things are over here.  Crazy from the heat.  Let me
> know if any of this perks some interest!
> Thanks Again
> Gavin

More information about the Synth-diy mailing list