[sdiy] Re: 4049 and 4069

[Czech Martin]

I guess it is the normal CMOS disease:
1/f noise, and the corner sitting at 100kHz
or higher, so all the excess noise sits in the
audio band.

After all, noise (in the sense of audio) was no
design or even process objective.
People who need to build CMOS linear amps
for audio spend a lot of time with this pesky
noise behaviour...

In fact, CMOS logic gates can be used as noise
source (linear, not time discrete shift registers).
You can see them on my web site.
http://www.geocities.com/SoHo/Museum/4459/circuits/cmosnoise.html

JFETs behave a little better, since no oxide
isolation. The basic Id/Ug characteristic is similar,
so why not building a distortion element with JFETs?

m.c.

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of jhaible
> Sent: Montag, 19. Januar 2004 20:53
> To: music.maker at gte.net; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Re: 4049 and 4069
> 
> 
> My 2 cents:
> 
> Yes, wonderful soft clipping from unbuffered CMOS. But also
> a little noisy. I wish I had such complementary MOS transistor
> pairs in a low noise version!
> 
> 15V (or /-7.5V) is what the chips can take, but the gain is
> much higher at low supply voltages.
> 
> JH.
> 
> -----Ursprüngliche Nachricht-----
> Von: Scott Gravenhorst <music.maker at gte.net>
> An: <synth-diy at dropmix.xs4all.nl>
> Gesendet: Montag, 19. Januar 2004 19:11
> Betreff: [sdiy] Re: 4049 and 4069
> 
> 
> > "Shokwave" <shokwave at nb.aibn.com> wrote:
> > >
> > >----- Original Message -----
> > >From: "harrybissell" <harrybissell at prodigy.net>
> > >
> > >> The 4049 may not work as well in linear apps as the 4069.  The
> transistors
> > >> in the 4049 are not a matched pair... they can (iirc) 
> sink much more
> > >current
> > >> than they can source.  The one time I tried a linear 
> circuit with them,
> it
> > >> oscillated
> > >> at the crossover point... causing me to have to redesign 
> the whole damn
> > >circuit.
> > >
> > >Well, thanks to Peter Snow being an awesome fellow, I have 
> a few 4069's
> as
> > >well! Anderton used the 4049 for his "tube-sound fuzz"...I 
> wonder what a
> > >4069 would sound like in there. I think I'm going to find out :)
> > >
> > >Of course, the fact that they AREN'T matched probably 
> contributed to the
> > >tubish qualities, shaping the waveform different above and 
> below the 0v
> > >line. Isn't it odd, I seem to find myself looking for 
> components with
> > >inexacting, "flawed" characteristics a lot (re "hunt for vactrols",
> "oooh, I
> > >found  j201's for cheap" etc). This is fun.
> > >
> > >-Darren
> > >
> >
> > Darren,
> >
> > I've done some work with the 4069UB (I don't know if there 
> is a buffered
> > version of 4069 at all, if so you don't want it for use as a linear
> > amplifier) and one thing I did notice about it (in linear 
> amplifier usage)
> is
> > that it's gain deteriorates as it's output approaches 
> either supply rail
> (Vss
> > or Vdd).  It does this in such a way that looks to me like 
> it mimics, to
> some
> > degree, the soft clipping of a tube amplifier.  So I 
> imagine that a 4069UB
> > might make a nice "tube distortion sound" device.  I've not 
> tried *that*
> per
> > se, but I have used this fact in a tri to sine shaper to 
> round things a
> bit.
> >  Under these circumstances, I got a very nice sound, very 
> sine-like.  I
> doubt
> > that it was a perfect sine, however.
> >
> > Also, one thing to remember about using either 4049 or 4069 
> in linear amp
> > mode is that the IC will draw more current than is spec'd 
> for logic use.
> > Bear that in mind when designing a supply for it.  They 
> also get slightly
> > warm.  The lower the operating voltage, the less current and heat.
> >
> > These parts can also be used with a dual supply, spec says 
> maximum of 15
> > volts (but an absolute maximum of 18) between Vss and Vdd.  
> This means
> that
> > +/- 7.5 stays within the strict spec advice, however, I've 
> used +/- 8
> volts
> > with no problem.
> >
> > Please keep us all up to date on anything you try!
> >
> >
> > =========================================================
> > - Where merit is not rewarded, excellence fades.
> > - Hydrogen is pointless without solar.
> > - What good are laws that only lawyers understand?
> > - The media's credibility should always be questioned.
> > - Governments do nothing well, save collect taxes.
> >
> > -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> > -- Linux Rex         | RedWebMail by RedStarWare
> > -- FatMan: home1.gte.net/res0658s/FatMan/
> > -- NonFatMan: home1.gte.net/res0658s/electronics/
> > -- Master of Arcane and Hidden Knowledge.
> >
> >
> 
> 
>