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Opamps - Die pictures

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Noopy:

Hi all,

if you are interested in more opamp die pictures I can post them here.


Till know I have taken pictures of a


Raytheon LM318

https://www.richis-lab.de/Opamp05.htm

Thomson LM318

https://www.richis-lab.de/Opamp06.htm

Sescosem SFC2741

https://www.richis-lab.de/Opamp07.htm

Signetics NE5534

https://www.richis-lab.de/Opamp01.htm

 :popcorn:

magic:
Coincidence: LM318 actually has a somewhat similar three stage topology to NE5534, although it may be hard to see it in this jungle of a schematic.
Capacitors are also connected in the same way, only one is not used (or perhaps not included in the datasheet). National's "Linear Brief" LB-17 explains a few things about this design.

Did you have some particular interest in this chip or just opened it because somebody from the forum sent you one?

Many precision amps like OP-07 or LT1028 (LT1115 is at Zeptobars) also use similar three stage topologies with similar compensation. LM118/318 was the first as far as I know.

BTW, those "adjustable" resistors appear to be simply pinch resistors. This has nothing to do with adjustments or precision of any kind, their tolerance is quite poor actually, but everything to do with producing high resistance on minimum die area.

Noopy:

--- Quote from: magic on June 10, 2020, 08:25:26 pm ---Coincidence: LM318 actually has a somewhat similar three stage topology to NE5534, although it may be hard to see it in this jungle of a schematic.
Capacitors are also connected in the same way, only one is not used (or perhaps not included in the datasheet). National's "Linear Brief" LB-17 explains a few things about this design.

--- End quote ---

Interesting!  :-+



--- Quote from: magic on June 10, 2020, 08:25:26 pm ---Did you have some particular interest in this chip or just opened it because somebody from the forum sent you one?

--- End quote ---

The opamps just appeared in my inbox.  ;D



--- Quote from: magic on June 10, 2020, 08:25:26 pm ---BTW, those "adjustable" resistors appear to be simply pinch resistors. This has nothing to do with adjustments or precision of any kind, their tolerance is quite poor actually, but everything to do with producing high resistance on minimum die area.

--- End quote ---

I agree with you principally.
I speculated whether Raytheon changed the length of the overlay to adjust the resistors. Indeed not very accurate...

Noopy:
Two more words about the suspected adjustable resistors.
Since they are pinch resistors they are commonly not very accurate. Anyway one can speculate whether Raytheon had a possibility to tune them (by mask modification perhaps).
It seems not plausible that Raytheon puts the least accurate resistors in places where they originally wanted the most accurate.

David Hess:

--- Quote from: magic on June 10, 2020, 08:25:26 pm ---Coincidence: LM318 actually has a somewhat similar three stage topology to NE5534, although it may be hard to see it in this jungle of a schematic.

...

Many precision amps like OP-07 or LT1028 (LT1115 is at Zeptobars) also use similar three stage topologies with similar compensation. LM118/318 was the first as far as I know.
--- End quote ---

Unlike those, the 318 uses emitter degeneration to lower transconductance of the first stage allowing better frequency response but this increases noise and drift making it unsuitable for audio and precision applications.  I think it was the first commercial integrated operational amplifier suitable for video applications.

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