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Reverse Protection of Input Power with Low Voltage Drop 2014-04-03

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crutschow submitted a new article:

Reverse Protection of Input Power with Low Voltage Drop - Prevent damage from accidental application of reverse voltage with minimal normal voltage drop.

Diodes are often used for protection from accidental connection of the power with reverse voltage. But they either suffer from voltage drop for a series diode, or requiring a current limit, such as a fuse, for a parallel diode connection. A parallel diode also applies a small reverse voltage equal to its forward drop under short-circuit current conditions when the reverse voltage is applied, which may or may not be a problem for the protected circuit.

For minimum forward drop and no reverse...
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That's a nifty idea, thanks!

I used a related configuration recently to clamp a signal input voltage that was normally close to ground but might exceed the supply; the connection was very similar, but with the gate tied to the supply rail.

This allowed a low-impedance coupling of the (high-frequency) signal when it was within the range of interest, whereas a rather high value resistor would have been needed using a diode-and-resistor clamp alone.
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