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[SOLVED] Purpose of Dual Voltage Power Supplies?

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Junior Member level 3
Nov 17, 2012
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What's the purpose of having dual voltage power supplies such as +12V/-12V? I know they can be used to increase switching speeds or reverse polarity of an inductor? But is there a difference between a +/- 6V power supply and a 12V power supply?

I'm assuming it's all history and convention and that current designs need to match other devices. Technically, isn't -12 -6 0, -6 0 6, 0 6 12, fundamentally the same, assuming the virtual ground is chosen at the middle of the designated positive and negative rails?


You're close - technically a 24V supply delivers the same potential difference as a +12V/-12V supply, and a virtual ground as you say would give you your 0V reference point. However, how would you implement a virtual ground? With a couple of resistors? If so, then your supply rails to 0V now have a lot of internal resistance, due to the resistors that you have added. On the +12V and the 0V virtual ground rail, you'd have very little current delivering capacity due to the resistance. You could try to solve it by reducing the resistors, but that would then just make them toasty.

Those classical dual rail power supplies are extremely ideal for op-amp circuits of course, as well as other analog circuits
that were popular in the past. Nowadays even multiple positive rails are useful too, since some parts of circuitry run at 5V, others at 12V, etc. Example being a computer PSU.
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