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### Topic: Rail splitter/virtual ground circuit trouble (Read 1 time)previous topic - next topic

#### alkopop79

##### Apr 13, 2013, 09:23 pm
I need virtual ground for a 741 op amp. The circuit schematics are here, the later can be simulated:

http://tangentsoft.net/elec/bitmaps/vgrounds/rdiv.png

https://www.circuitlab.com/circuit/y9x79d/rail-splitter/

I have simulated the circuit in three different programs an it always seem to work. However, when I build the circuit on the breadboard, it doesn't work. With 9V DC supply instead of getting 4.5V, 0V and -4.5V I get 9V, 4.5V and 0V. It seems as if the caps weren't even in the circuit. I checked the polarity and the value of the caps and even used different ones. Still don't get any virtual ground, the circuit acts as a voltage divider. A photo of the breadboard circuit:

http://www.flickr.com/photos/alkopop79/8646491414/.

The circuit is damn simple, it puzzles me why it doesn't work. Again, I checked polarities, power, etc. Any help would be appreciated!

#### afremont

#1
##### Apr 13, 2013, 11:13 pm
You have to stick your meter ground lead on the Vgnd (middle) location.  You will then see +4.5V and -4.5V relative to that.  You connect the Vgnd to your op-amp circuit ground.  You power your op-amp from the outer (+4.5V and -4.5V) locations.
Experience, it's what you get when you were expecting something else.

#### Grumpy_Mike

#2
##### Apr 13, 2013, 11:20 pm
The 741 is a very old chip. When you operate it on VS =±5V, the output will only be VO =±2V. Even so that can't be fed directly into an arduino because the +2V is sitting on the +5V center rail and will feed too much voltage into the arduino.

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