I have an application where I need to supply an op-amp circuit from a single rail - and it needs to be dc-coupled. I saw this circuit which produces a phantom ground
(Fig 7)
But was unsure what *ground means in the diagram. I assume phantom ground is the op-amp output is it?
Also this one here
differs in that c2 goes to the *ground - so I am confused...
Thanks
Hi,
Yes, but this Picture is a little wrong ;-)
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
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.)
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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