Diode after a clamping diode

[Keno]

A questions came up in one of my Electrical III classes today, what would the purpose of a diode after a clamping diode be?

 

[misterT]

Can you post a schematic?

 

[Gary B]

It depends upon its polarity. If forward biased, the first thought that comes to my mind is that it cancels out the forward voltage drop of the clamping diode by dropping the same amount of voltage as the clamp thus ensuring the circuit input can never exceed the power rail.

 

[MrAl]

Hello,


Yes it would help a lot to see the actual circuit or a typical circuit here.

 

[Keno]

I think this is how the schematic goes, if its not ill upload it again.

 

[MikeMl]

The diode to ground is useless, unless you need to subtract 0.7V from the 12V supply.

 

[BobW]

The diode to ground will protect the other diode from burning out if the battery polarity is reversed.

 

[Keno]

Ah cool thanks. I asked a friend who is a auto major and he said the same as you Bobw!

 

[MrAl]

Hello,


Yes it appears to be a simple reverse polarity protector. Without it the fuse would blow if the polarity was accidentally reversed. With it in there if the polarity is reversed nothing happens so the operator knows they have got it backwards, and after correcting the polarity then it suddenly works fine without having to change the fuse.

 

[audioguru]

I think the schematic is a little on the dark side.