[sdiy] IN your mind, what is ....

[jhaible]

> > So, has there been a "Norton amp" before the 3900, or was the
> > word introduced to describe this chip?
> >
>
> I think the reference is to it's current nature.

Certainly. Just as constant current diodes are called "Norton Diodes".

But I still wonder if National initially decided to create a quad
monolithic version of current differencing amp (to offer an
integrated version for a similar discrete building block), or
if it was just a happy accident.

It *looks* like an ordinary opamp with the pnp input stage missing.
(The npn current mirror forming an active load for that missing
input stage - see that ARP 4pole VCF, with the capacitor disconnected ...)
I can imagine that at some point, maybe after some trouble with the
pnps, they just said hey, this will make a useful chip just as it is !!
(Only a wild guess, of course.)

JH.





 Voltage analysis of a
> circuit is call "Thevenin" equivalent circuits and current analysis is
> called "Norton" equivalent circuits.
>
> Takken from "Transform Circuit Analysis for Engineering and Technology" by
> William D. Stanley. A good book an the Laplace transform.
>
>