# Need help with understanding a clamping diode in a circuit

J

#### [email protected]

Jan 1, 1970
0
Can someone show me in the most generic form how a clamping diode
works? I have some cicuit anaylsis background from years ago, but I
cant seem to remember coming across this item. I've read the theory but
I still don't see it in a real circuit and how it "clamps". Are there
different ratings on clamping diodes? Basically I have a problem with a
transient spike that jumps from nominal 20V dc up to 30V dc and down to
-10V dc in about 1ms time. I'm was told a clamping diode will work.

Thanks

J

#### John Popelish

Jan 1, 1970
0
Can someone show me in the most generic form how a clamping diode
works? I have some cicuit anaylsis background from years ago, but I
cant seem to remember coming across this item. I've read the theory but
I still don't see it in a real circuit and how it "clamps". Are there
different ratings on clamping diodes? Basically I have a problem with a
transient spike that jumps from nominal 20V dc up to 30V dc and down to
-10V dc in about 1ms time. I'm was told a clamping diode will work.

Thanks

There are two distinct ways to clamp voltage peaks with diodes. one
involves a diode from the signal line to a supply voltage or ground
that becomes forward biased when the signal voltage gets one diode
drop (about .3 volts for silicon Schottky diodes and about .6 volts
for silicon junction diodes) past the particular supply voltage. This
provides a low impedance path for current that tends to load the
signal voltage down if it tries to go further.

The second method involved putting a device between the signal and
ground that has a high impedance up to some breakdown voltage, and
switches to a low impedance for higher voltages. A zener diode is the
classic example of this sort of clamp but there are lots of
variations, including Metal Oxide Varistors for higher voltages and
bidirectional high surge current zeners. These devices turn the
energy that would have produced an over voltage into heat.

Replies
6
Views
899
Replies
11
Views
2K
Replies
13
Views
3K
Replies
4
Views
2K
Replies
3
Views
860