inverters used in analog circuits... how?

[Fp-www.Tonepad.com]

I am looking at the mxr Envelope filter with all those inverter stages, and I'm wondering what is the theory behind those.

Can somebody point me to a simple tutorial on how the inverter stages are used in analog circuits?

Fp

[toneman]

did U Google at all?
basically, the 1M resistor from the output 2 the input biases the
digital inverter 2 the linear region.  So instead of action "ON/OFF",
it now "amplifies" or has gain.
other's i'm sure will elaborate or point 2 a good web site...
staybiased(linearily)
tone

[amz-fx]

I don't have a schematic in front of me but as I recall the inverters (4049) are used as gain stages and the cmos switches (4066?) are used to make a switched-capacitor filter in conjunction with them.

regards, Jack

[puretube]

I`m really, totally, completely, and overwhelmingly
brutally being over-asked by this question...
I`ve been wondering myself, if they can be replaced by some
v*ero-layout with led-controlled expression-pedal,
or a PIC-simulation...

maybe an answer can be found here:
http://diystompboxes.com/sboxforum/viewtopic.php?t=34595
or here:
http://diystompboxes.com/sboxforum/viewtopic.php?p=242223#242223
:?:  :?:  :?:

:roll:

[toneman]

Jack's right on the money!!
Without *even* looking at the schemo!!
PT can control the 4066s with a PWM PIC.
Actually, U could control *several* filters like this with *one* PIC (16F84)
Now, has anyone figured how to use a PIC in the "linear" mode??
Call me if U have......
:lol:

[niftydog]

well, I'm fairly PIC savy, but not sure what you mean by "linear mode". can you expand on what it is you want to acheive?

[toneman]

my tongue was in my cheek, ND.
unless.......there's an A/D inside it.....
...like the PIC 16F1220..............

[niftydog]

ah ok. a lot of PICs have A/Ds and some have PWM outputs which can approx. analog outputs.

[R.G.]

Can somebody point me to a simple tutorial on how the inverter stages are used in analog circuits?

National Semiconductor CMOS Data Book, "Linear Applications of CMOS Logic", about 1976. They may still have this app note on their web site.

I am looking at the mxr Envelope filter with all those inverter stages, and I'm wondering what is the theory behind those.

(a) any inverting amplifier may be used as a linear amplifier with feedback if it has enough gain and a fairly linear region of amplification. CMOS single inverter stages qualify, at least the unbuffered ones. They have an open loop gain of about 30, so they can be used with feedback for gains lower than that with little trouble. Buffered CMOS gain stages have quite large gains, but there is no provision for compensating them to be stable with feedback. Unbuffered stages have low enough gain and phase shift and high enough frequency response to be stable with simple feedback.
(b) CMOS gain stages have reasonably complementary input devices and P/N channel characteristics, so with unity DC feedback they will bias close to the middle of the supply.
(c) For the theory of what gains you get when you feed back inverting amplifiers with limited gain, do a google search on negative feedback theory. The bottom line is that a feedback amplifier with an inverting gain of infinity and an infinite input impedance will give a closed loop gain asymptotically close to Zfeedback/Zinput. This simplifies to Rf/Ri for cases where you can ignore the reactive components. The gain only approaches Rf/Ri. With lower and lower gains, the "gain error" gets significant. You need an open loop gain at least ten times your desired closed loop gain to get close.

Is that the kind of thing you're looking for?

[niftydog]

found this at Fairchild, it's either the one or very similar to what R.G. was referring to.

[puretube]

SEARCH:  

(the strange behaviour of the forum-software (see "report problems here"-thread...) led me to that funny posting a couple hours ago...)  :roll:

[R.G.]

found this at Fairchild, it's either the one or very similar to what R.G. was referring to.

It's the same one. Looks like Fairchild and National used the same sources.