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

[jhaible at debitel.net]

> > Quoting the LM3900 designer once more:
> > "Because application design approaches are very different
> > from those used with standard opamps, the LM3900 is usually
> > not called an opamp to avoid confusion with standard
> > opamps."
> 
> Indeed.  Technically the LM3900 is a Norton opamp.

Sure. Maybe it even was the other way round, and the LM3900
first coined that word, Norton opamp?
Are there any predecessors for such a current mirror input
device?


> But hey, the Philbrick "brick opamp" of the 1960s didn't have much gain 
> above 100 either!  

Yes, that's technical progress ...
Today's state of art is tomorrow's junk - or vintage device, depending
on your application. For many audio applications, you don't need
an "operational" amp at all - you just need an amp. Discrete, when
I have the choice. And with a single transistor input stage, because
the second half of a differential pair will add 3dB of noise. (;->)
(But then again, try building a GIC or FDNR filter from a LM3900 or a 
Philbrick opamp ...)

BTW, when Harry speaks of Bob Pease dissing that LM3900 (Hi Harry!)
this is from _today's_ point of view. Back then, he wrote the
foreword to that Fredriksen Book where the 3900 is presented as an
important part of National's opamp history. And he gave me that book
with the comment that it's still valuable reading today. (;->)

JH.

-------------------------------------------------
debitel.net Webmail