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Transform an Unipolar Power Supply into a Bipolar Power Supply

artificial Ground artificial Ground artificial Ground

The Approach used here is just an active Voltage Divider. The GND of the Output just has to be centered between the positive and the negative Supply. This can be achieved using a Power Opamp such as the L149 (4A) or the L165 (3A) or any equivalent type beeing available at your local hardware store. The Schematics below shows how to wire it ...

3 Amp. Version using L165 from SGS Thomson.
C2 and C3 may be realised with 100µF // 100nF

Schematics L165 active Power Split

The Connections on the left side are considered to be the Inputs whilst the Connections on the right side form the Output. The Picture below shows the Pinout of the L165 Power Operational Amplifier from SGS Thomson. The Voltage Divider formed with R1 and R2 holds the positive Input of the OPAMP at half the Supply. As the OPAMP is connected as Voltage Follower or Impedance Converter, the Output (which is connected to the negative Input) will always try to reach the Voltage at the positive Input. It will remain exactly centered. (If you do not excruciate it to much :-)

Pinout L165

4 Amp. Version using L149 from SGS Thomson.
C2 and C3 may be realised with 100µF // 100nF

Schematics L149 active Power Split

As this productuct is obsolete - check availability first !!! - or translate this knowledge to any other (newer and much better OPAMP)

When using the L149 the Schematics has to be expanded a little bit. One more OPAMP has to be added to achieve the desired function. The Schematics above shows how to wire it.

We thank Mr. Andrew Huber for his valuable Input and the Discussions about active Power Splits.

We thank Mr. Thomas Schaerer for pointing out, that the capacitors C2 and C3 greatly improve the high frequency behaviour. Also the ability for oscillation may increase if you choose the wrong Opamp. Read more here (in german languange).

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t1 = 6587 d

t2 = 250 ms

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