This is an op amp?

[CJ]

This is listed as an op amp in the DBX patent sheet for the 2001 VCA. The stuff in the box, that is. I see a current source and an amp, I'm cool with that. But op amp? The wire leaving on the right is the output. Feedback wire coming up to input.

Anybody xplain to a dim wit?
Sorry for the low res, but at least you don't have to click on it.

J201, top and bottom.
Thanks!

 

[bcarso]

Well, it's an amplifier with inverting gain anyway, which could be used with feedback from output to input. So, no differential input per se, although the lower source can be considered a non-inverting input that is tied to ground.

A lot of the early analog computing amplifiers had only inverting inputs, and that's where op amps originated, so I guess they wre within their rights to describe that section as such, albeit a little perverse considering the date of the application.

 

[CJ]

Ooops, sorry for the confusion on the date, 2001 is the model, probobly late 70's.

And thanks for the reply!
Makes sense.

 

[gyraf]

[quote author="bcarso"] A lot of the early analog computing amplifiers had only inverting inputs, and that's where op amps originated, so I guess they wre within their rights to describe that section as such, albeit a little perverse considering the date of the application.[/quote]

Half of the art of writing patents is obscuring the actual information beyond recognition..

Jakob E.

 

[clintrubber]

But op amp?

Sometimes even a single BJT is considered/said to perform an opamp-like function (ignoring the Vbe-shift).
Like: AC-signals equal on B & E, and if not, then drive results, making them the same again.
You'll need additional circuitry of course for that last bit, but OK, the idea is valid.

 

[jhaible]

[quote author="clintrubber"]

But op amp?

Sometimes even a single BJT is considered/said to perform an opamp-like function (ignoring the Vbe-shift).
Like: AC-signals equal on B & E, and if not, then drive results, making them the same again.
You'll need additional circuitry of course for that last bit, but OK, the idea is valid.[/quote]

Yes. Also, the application might need an "opamp with current output". Then the common source amp, working into a constant current load (the upper FET), makes sense.
Does this output, by any chance, go to some emitters of BJTs in a variable gain cell?

JH.

 

[clintrubber]

Sometimes even a single BJT is considered/said to perform an opamp-like function

And of course the same holds for FETs, triodes etc etc.

Hey, as long as you put the right circuitry around it and with a little determination I figure we could even consider a TX as an opamp ! :wink:

 

[tmbg]

[quote author="clintrubber"]
Hey, as long as you put the right circuitry around it and with a little determination I figure we could even consider a TX as an opamp ! :wink:[/quote]


Messers Horowitz and Hill are pretty clear when they say that a transformer does not qualify as an op amp because there's no power amplification.

 

[clintrubber]

You're fully right of course, I wanted to add all kinds of stuff about a TX being & remaining a passive thing so it can't really be etc etc...
...but I didn't ! :wink:

 

[CJ]

I get it..."passive .....but I didnt"....very subliberated or whatever.

:green:

 

[clintrubber]

:grin: :thumb: