Future Trends in IC Opamps

[jackinnj]

from 1968

http://www.edn.com/index.asp?layout=...leID=CA6371161

[Nelson Pass]

Back in 1968, the designers I admired in turn admired Widlar.

[Wavebourn]

..and you see, there were no single word about audibility of distortions...

[FastEddy]

... that article and Mr. Widlar's work was reprinted / rewritten in Popular Electronics then expanded into "cook books" of op-amp circuits ... most of which is still valid and useful.

I remember reading all of this stuff over and over, then getting some very expensive samples from Alalog Devices and Fairchild Semi and breadboarding some really cool stuff.

" ... no single word about audibility of distortions ... " If you paid attention to the Slew Rates, you could make audio pre-amps from these with quite respectable distortion numbers ... of course keep 'em from oscilating was a neat trick.

[Leolabs]

Originally posted by Wavebourn
..and you see, there were no single word about audibility of distortions...

Maybe he dont think that people will use OPAMPs for high quality audio purpose.

[lineup]

Conclusions

Bipolar transistors probably will continue to play the dominant role
in integrated-circuit development in the foreseeable future.

Devices will be built providing input currents of 1 nA over the full military temperature range,
along with offset voltages of 2 mV.

The use of trimmed hybrid resistors to obtain even lower offsets is expected to be important in the military market
where potentiometers of adjustments cannot be used.

For demanding full-range applications,
temperature-stabilized bipolar circuits promise the best performance
and fewer technological difficulties.

-----------//----------

Junction FET's appear to be a temporary solution to the input current problem,
but the fact that adjacent devices do not give low offset
is expected to limit their success.

Further, when temperature-stabilized, their leakage currents can be expected to be about the same magnitude as the bias currents of bipolar devices,
so they offer no advantage.

-----------//----------

As for other parameters, there appears to be little motivation to make improvements, except in the areas of simplifying frequency compensation and making the amplifiers impervious to abuse.

The Conclusions are interesting.
We can expect an era of BIPOLAR Op-amps using bipolar input,
but with as low input current as 1 nA!



lineup

[lineup]

Originally posted by lineup


The Conclusions are interesting.
We can expect an era of BIPOLAR Op-amps using bipolar input,
but with as low input current as 1 nA!

lineup

What makes me suspicious, is the date.
Is this article from 1968 ????

.
Future Trends in IC Operational Amplifiers

By R. J. Widlar -- 6/10/1968

EDN
.

[clem_o]

lineup,

Look at the first post, from jackinnj... I think that's pretty clear...

Cheers

[jackinnj]

Widlar developed National's first big chipamp -- the LM12.