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Single Rail Op-amps

M

Marte Schwarz

Jan 1, 1970
0
Hi,
http://www.analog.com/library/analogDialogue/archives/35-02/avoiding/

(Fig 7)

But was unsure what *ground means in the diagram. I assume phantom
ground is the op-amp output is it?

Yes, but this Picture is a little wrong ;-)
http://www.edn.com/contents/images/200380f7.pdf

differs in that c2 goes to the *ground - so I am confused...

Place C2 to one pole of the battery. The resistors don't have to be
symmetrical, especially if the amplifier isn't symmetrically too. TLC27x for
example can reach negative rail but not the positive. with 3V3 supply there
is only 2V useful. There we use 1V as "virtual ground".

Hey Jörg, kannst Du mal übersetzen? Wir sprechen hier gern von
"Bezugspotential" im Gegensatz zu "Masse". Fürs Englisch kenn ich da immer
nur "ground". Aber "Erde" ist dann ja doch noch einmal was anderes, nicht?

CU
Marte
 
K

kell

Jan 1, 1970
0
Hi,




Yes, but this Picture is a little wrong ;-)



Place C2 to one pole of the battery.

In the analog.com paper, somebody got lazy. They had arrived at each
previous diagram by making a slight modification to the one before --
leaving component values, ground symbols etc unchanged. They
continued that practice into diagram #7. Wrong!
And what about the bypass caps on the power pins of the op amp in that
diagram. Doesn't it look like they should go to the battery?

When somebody at edu.com needed a diagram, he apparently copied
diagram #7 off the analog.com paper without examining it carefully.
(You will notice that along with having the same error, it has the
identical component values.)
 
G

Gerhard Fiedler

Jan 1, 1970
0
Hey Jörg, kannst Du mal übersetzen? Wir sprechen hier gern von
"Bezugspotential" im Gegensatz zu "Masse". Fürs Englisch kenn ich da immer
nur "ground". Aber "Erde" ist dann ja doch noch einmal was anderes, nicht?

Nicht Jörg, aber vielleicht trotzdem: Masse ist normalerweise "ground".
(Schutz)erde ist "safety ground". Bezugspotential könnte "reference
voltage" sein, oder auch "virtual ground".

Gerhard
 
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