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Note in the CD4000 series there is a hex inverter of the
3-stage type, and one that is on purpose a single stage,
meant for use in crystal oscillators and such where 3
stages makes unacceptable phase lag and some chance
of small signal self-oscillation or phase-shift oscillation.
The unbuffered invs are CD4009UB, CD4049UB, CD4069UB
per TI current-day conventions. In an old RCA databook
the CD4049A and CD4069A show as a single stage inverters
but you'd want to verify the naming scheme on present-day,
different-vendor product lines (TI bought the family from
Intersil later on and has been editing stuff per their own
interests, since). There's also (I think) been some divergence
between the CD4000B and CD4000A branches over time...
The 4069 cmos inverter IC (unbuffered version 4069UBE) can perform the role of analog amplifier. Many schematics have 3 inverters in sequence with feedback resistors added.
Klaus is right. Don't use one if a 'real' amplifier is available. Only un-buffered 4069 inverters work and their performance in linear operation is poorly defined. Expect high noise and bad linearity. The mid-voltage point may also vary considerably from one gate to another.
In RF frontends the current regulated inverter with resistor feedback is not rare, as its noise figure is low thanks to NMOS and PMOS transconductance are added. Its linearity is not worse than a cascoded NMOS amplifier, bandwidth is similar.
Maximum gain is (gm.n+gm.p)*Rout~(gm.n+gm.p)*Rfeedback considering resistive feedback for biasing and capacitive load.
4069 is an example for a CMOS inverter, but it is a discrete device designed for low speed logic. Even its ESD protection is not designed for RF, I can imagine that it is enough to couple all supply noise to its input, but without current regulation its supply(noise) dependence is high too. For audio I agree it is a terrible choice.
Do a quick measurement, strap a 10 Meg R across the inverter, drive AC coupled function
generator into it, and measure its max G. I would use spit screen with FFT to keep
an eye on harmonics/over driving the gate.
If you want a more involved look use a Nano VNA to get phase response as well.
But keep in mind device to device, even on same die, will exhibit large variance.
It was not optimized as a G element. So circuit design cannot rely on a known
accurate closed loop G.
The severe audio distortion might be used as an electric gEEtar fuzz producing circuit.
Here is a test a long time ago for only one of them. Some will have much more gain and others will have much less gain:
The severe audio distortion might be used as an electric gEEtar fuzz producing circuit.
Here is a test a long time ago for only one of them. Some will have much more gain and others will have much less gain:
I am using auto-biased inverters for an application where speed is key and cal can be done before the "science shot", while closed loop BW would ruin the pulse to detect & quantify. Especially as the science in question jacks every junction in the chip, simplicity offers a way to get it done.
Expect gain of about 10, gross nonlinearity and a very limited "linear-ish" range and mucho PVT variation.
Note in the CD4000 series there is a hex inverter of the
3-stage type, and one that is on purpose a single stage,
meant for use in crystal oscillators and such where 3
stages makes unacceptable phase lag and some chance
of small signal self-oscillation or phase-shift oscillation.
The unbuffered invs are CD4009UB, CD4049UB, CD4069UB
per TI current-day conventions. In an old RCA databook
the CD4049A and CD4069A show as a single stage inverters
but you'd want to verify the naming scheme on present-day,
different-vendor product lines (TI bought the family from
Intersil later on and has been editing stuff per their own
interests, since). There's also (I think) been some divergence
between the CD4000B and CD4000A branches over time.
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