[sdiy] How To Make This Oscillator into a VCO

[Gavin]

yes, linear response is a big drawback as far as integration into a modular
system, etc.  But as a VCLFO or a ring mod carrier generator it's a nice
simple solution.  Looks quite a bit like what you used to get from the 550
(?) VCO IC.
Single supply?  even better, also there's a (sort of) puzzling note on the
schematic.  at the non-inverting input of the comparator op amp we see V+/2
which I'm assuming is half the supply voltage, to achieve a true square off
the comparator.  I think perhaps it's the internal temperature compensation
that makes the 324 the god choice for this application.
----------
>From: patchell <patchell at silcom.com>
>To: Gavin <elmystico at earthlink.net>
>Subject: Re: [sdiy] How To Make This Oscillator into a VCO
>Date: Sun, Oct 20, 2002, 2:00 AM
>

>    I would have to look at the circuit again...but I think that the common
>mode input range needs to include the negative voltage terminal on the opamp.
>This is strictly a single supply type application, although, I could be wrong.
>
>    One big disadvantage of this circuit is that it is stricktly linear
>response.
>
>Gavin wrote:
>
>> Wow! nice circuit, now ill this work with other op amps?  or is it specific
>> to the properties of the lm324?
>> ----------
>> >From: patchell <patchell at silcom.com>
>> >To: bill berzinskas <housenationmedia at yahoo.com>
>> >Cc: synth-diy at dropmix.xs4all.nl
>> >Subject: Re: [sdiy] How To Make This Oscillator into a VCO
>> >Date: Sat, Oct 19, 2002, 4:46 PM
>> >
>>
>> >    Yes it can...look in a National Semiconductor data sheet for the
>> >LM324.  There is a VCO that will produce a triangle that uses no OTAs.
>> >In fact, this is what I built for my first synthesizer back in 1974.
>> >Worked a lot better than the Paia 2720 oscilator...in some ways.
>> >
>> >bill berzinskas wrote:
>> >
>> >>    Thanks for all the good responses..  tons of good info..
>> >>
>> >>
>> >>
>> >> Next Question:   Can this be done without an OTA?  For the most part,
>> >> i'm working with standard opamp pieces..
>> >>
>> >>
>> >
>> >--
>> > -Jim
>> >------------------------------------------------
>> >* Visit:http://www.silcom.com/~patchell/
>> >*-----------------------------------------------
>> >*I'm sure glad Merry Christmas comes just once a year
>> >* -Yogi Yorgensen
>> >------------------------------------------------
>> >
>> >
>
>--
> -Jim
>------------------------------------------------
>* Visit:http://www.silcom.com/~patchell/
>*-----------------------------------------------
>*I'm sure glad Merry Christmas comes just once a year
>* -Yogi Yorgensen
>------------------------------------------------
>
>