Triple Output Tracking Power Supply Uses Standard 3-Terminal Regulators, Adjusts to Zero Out 2017-03-09

[crutschow]

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Dual Tracking Power Supply Using 3-Terminal Regulators, Adjusts to Zero - Plus/minus tacking supply using common 3-terminal regulators can go to zero volts out.

Here's a variation on a dual output tracking power supply using the common LM317 and LM337 3-terminal regulators that allows their outputs to be adjusted from the maximum down to 0V instead of the typical 1.25V.
The output of an LM317 is nominally 1.25V greater than he ADJ pin, thus the minimum output is 1.25V if the ADJ pin is connected to ground.
The circuit below adds an additional LM337 (U3) to generate -1.25V as a reference voltage for U1's ADJ terminal, allowing its output to be...

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