plot

put a capacitor in parallel with each resistor as suggested, should work. it's what i do whenever i'm powering an opamp from a single supply.. never had a problem with it.

ikalogic

thx

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Ibrahim Kamal
check my electronics and robotics page: http://www.ikalogic.com/

ikalogic

hi
why does and op-amp for a dual voltage poer supply is better than just a simple voltage divider?
what makes it so special ?

i have heard b4 about using op-amps for dual voltage supply but never understood why ..Thx

__________________
Ibrahim Kamal
check my electronics and robotics page: http://www.ikalogic.com/

Nigel Goodwin

A potential divider is fine, as long as the current drawn from both the positive and negative rails is the same (or very similar). Using an opamp to generate the split supply allows them to be different (within reason), the opamp corrects for the difference.

Roff

Expanding on what Nigel said:
The problem with using the voltage divider without the op amp is that if the loads on the supplies vary, the supply voltages will fluctuate relative to the "ground" created by the divider. This may not be a big problem for other op amps in the circuit, because they generally have good supply rejection, but it can wreak havoc on other circuits using the same supplies. For example, a common-emitter transistor amplifier generally has very poor power supply rejection. Fluctuations of the supply voltage will show up on the output. Circuits such as these are one of the reasons we use voltage regulators.
I have re-posted the schematic of the circuit with the buffered ground below.

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