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Op-amps with single supply or dual supply ?

Question asked by colliard-piraud sylvain Employee on Apr 6, 2012
Dear forum members,

Perhaps, you wonder what is the difference between single and dual supplies ?
Or maybe if the op-amp will have the same behavior with Vcc= 0 -> 5V or Vcc= +/- 2.5V.

It is important to keep in mind that all voltages have a reference. It means that we have to think : difference of potential.
Most of the time, when we say Vcc=5V, it means a potential difference of 5V referenced to the GND : 0V.

As a conclusion, we can deduce that both of the following configuration will have the same behavior :
single_dual_supplies_4.png               single_dual_supplies_5.png
               


But, there is a point that you should take into consideration.
In your application, it is not as simple as it looks like to switch from one configuration to the other one. Actually, you have to take into account all your voltages.
Here you can find a simple example in order to illustrate it, if you want to switch from a configuration with Vcc= 0 -> 5V to a configuration with Vcc = +/- 2.5V :
 single_dual_supplies_1.pngsingle_dual_supplies_8_arrow.pngsingle_dual_supplies_6.pngsingle_dual_supplies_8_arrow.pngsingle_dual_supplies_7.png

Actually, in the 2nd configuration the output voltage won't have the same behavior than the 1st one : the op-amp will be saturated.
That's why it is important to take into account all voltages and not only the power supply voltages.

Best regards,
Sylvain Colliard-Piraud

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