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Dumbest "equivalent schematic" from a datasheet - how many errors can you find?

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EPAIII:
RE: "#2 Trivial"

IMHO, there is nothing trivial about this.

I have never liked the convention of drawing schematics without using the overpass style wire crossing where there is no connection. This NON-trivial error is the best argument for that dislike. And the fact that it has apparently survived over a long period speaks against any arguments that will be made against my dislike.

Not only was it an easy error to make, not only does that error render the circuit non-functional if followed, but apparently no one sees any real need to correct it even when told about it.

This style of schematic should not exist. It should have never existed. All existing such schematics should be properly updated with the overpasses ASAP by the original creators. And the original creators should not be paid a single penny for do this. And copies should be distributed by those creators IN PERSON, taking the time to insert them in place of the original, defective schematics in whatever form those originals may have taken.

Rid the world of electronics of this scourge! NOW!




--- Quote from: fourfathom on March 26, 2022, 07:36:33 pm ---(#1) PNP output transistor base-emitter short.
(#2 Trivial) Missing Vcc connection dot.

--- End quote ---

T3sl4co1l:
Meh, overpasses are old fashioned (and still subject to transcription errors all the same).  Current best practice is to never use 4-way junctions, except for crossings.

Which, the above circuit seems to take advantage of otherwise: the output is dog-legged from the current sense B-E shorting wire, for instance.  And then the capacitor and IN+ cross in an orderly fashion as we expect.  But then Vcc goes into a damn current source, and all bets are off. :)

(Another reason against overpasses is the implication of orientation, ordering, or z-height, an irrelevant detail -- a minor one to be sure, but it does technically add to the visual noise.  Conversely, one might argue the 3-way junction rule, harnesses visual noise instead: such connections tend to be less symmetrical, arguably uglier -- which highlights their importance, in a way.)

Tim

magic:
Which is funny because TI is normally very religious about avoiding four-way junctions.
I gather that they really meant to connect VCC to that damn current source rather than everything else :-DD


They are similarly obsessed with never drawing current mirrors with a single line crossing through all bases (like everyone else) but snaking around those transistors and branching off to each base ::)

Zero999:

--- Quote from: magic on March 26, 2022, 09:36:36 pm ---- are polarities of the inputs even right?
--- End quote ---
I admit, the only error I saw was the inputs reversed. I can't believed I missed the missed the base-emitter short on the output transistor.

--- Quote from: bsfeechannel on March 26, 2022, 09:39:08 pm ---LM358 equivalent circuit for comparison.



--- End quote ---
The drafting errors are more obvious and indeed understandable, after seeing the original, nut why didn't they simply copy and paste it? It's probably even the same die as the LM358, just with only one half connected.

Ed.Kloonk:

--- Quote from: magic on March 26, 2022, 09:36:36 pm ---I did take it from the current datash*t ;)
But you aren't wrong, it goes back all the way to 2005.

Still one blatant error to go. Hint:
- are polarities of the inputs even right?
- would it be stable without a whole bunch more compensation?

OTOH, I just noticed that the connection of the current sink to output PNP base is not actually technically wrong, because the base is shorted to the output anyway. So perhaps one less than I thought :D

--- End quote ---

Fascinating thread.

My spidey sence makes me wonder if they might of done that to try and catch counterfeiters.

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