Odp: [sdiy] inversion, CMOS, etc.

Roman modular at go2.pl
Fri Aug 2 23:33:30 CEST 2002


1. If the pulses are short, or happen not too
often, that is if mean value
of the voltage here is almost 0V, you can simply
use inverter, capacitor and
resistor. Make C and R appropriate values to your
usual pulse duration,
say if its 1us, make C*R=5us, meaning C=4n7, R=1k.
Other, cleaner solution will require negative
supply anyhow.

2. Feed your +/-5V signal thru resistor divider.
One end to input, other
to +5V, middle to your comparator. OTOH you say to
leave the wave
itact and cut the lower peeks, so you simply need
a resistor and a diode
to ground.

3. Maybe it's to late for me to get it, but I
thought every comparator
is voltage controlled, as it... compares voltages.
What else would you like
to control in it with voltage?

Roman

----- Original Message -----
From: gavin <elmystico at earthlink.net>
To: synth <synth-diy at dropmix.xs4all.nl>
Sent: Friday, August 02, 2002 10:27 PM
Subject: [sdiy] inversion, CMOS, etc.


> 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




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