Linear Bias CMOS Inverters for not distortion functions

[Bill Mountain]

I am working an a mixer project that will make use of a lot inverting opamp stages (at least four).

I have a crap load of UB4049's that cost me about $0.40 ea.

I know they are not perfect representations of opamps but are they close enough to be used as active mixers and active filters or am I just asking for too much out of them?  Am I being blinded by mojo?

Who hasn't wanted a pocket sized "TUBE SOUND FUZZ MIXER"

I figure not only are there so many inverters available in the chip but the biasing is much easier and they have a tone of headroom.

Thought?

Concerns?

Criticisms?

[composition4]

I know this isn't helpful and doesn't directly answer your question... but... yeah... 80c each

http://au.mouser.com/ProductDetail/Texas-Instruments/TL074CNE4/?qs=sGAEpiMZZMtCHixnSjNA6Dh9CQmOfcFcWC%252bLpGtMkR0%3d


is it really worth messing around with inverters? just sayin'

for someting more useful to your question, take a look here:

http://www.diystompboxes.com/smfforum/index.php?topic=34050.0

[Bill Mountain]

I know this isn't helpful and doesn't directly answer your question... but... yeah... 80c each

http://au.mouser.com/ProductDetail/Texas-Instruments/TL074CNE4/?qs=sGAEpiMZZMtCHixnSjNA6Dh9CQmOfcFcWC%252bLpGtMkR0%3d


is it really worth messing around with inverters? just sayin'

for someting more useful to your question, take a look here:

http://www.diystompboxes.com/smfforum/index.php?topic=34050.0

Great point.  Tayda's got for $0.26:

http://www.taydaelectronics.com/tl074-quad-operational-amplifier-j-fet-pdip-14-tl074cn.html

I guess I have my MOJO blinders on.

[Bill Mountain]

It's interesting.  R.G. states that Hex Inverters make great buffers and can be used as filters with low gain (unless I'm reading it all wrong).  This is 99% of what this project is doing.

[amptramp]

I used to design low-noise amplifiers for infrared scanners and we did some odd experiments on occasion.  One was to run a CMOS inverter at liquid nitrogen temperatures (77K = -196°C) to see if we got acceptable noise.  We didn't get anything better than other designs we had due to the diode/resistor ESD protection at each input and we got occasional cracking sounds that corresponded to blips on the screen.  One other thing we saw was that even though CMOS is a low power technology when used as a digital gate, when biased in the linear mode, each inverter took 8 mA.  If you are running at 9 volts, this is 288 mW for four sections.

I would use a TL074 for this kind of thing but there are people who have success with CMOS gates in linear mode so by all means, try it out.  The headroom may not be as large as you think - these are designed as digital devices and they switch rail to rail within a volt or so around the Vcc/2 input point.

[Bill Mountain]

The headroom comment is based solely on the ear bleedingly high output of my Tube Sound Fuzz.

I'll stick with opamps I think but it's always fun to experiment.

[anotherjim]

You could still use a few of the 4049's in a mixer. Add an alternative "Valve sound" output bus and have a couple of "Valve sound" input channels.

[Bill Mountain]

I wonder...would it really be "tube sound" if little to no gain is applied???

[PBE6]

Depends how much you pay for it!