Effectiveness of p6ke39ca clamping diode

Jan 05, 2005 2 Replies
R

Hey all,



I need to clamp a transient voltage (around 5-10 us) which can rise up to 20V +ve and 20 V -ve i.e. 40 V pp to +/- 5V. The frequency of this voltage varies from 10 to 15 MHz.



I was thinking of the p6ke39ca bi-directional diodes to clamp this voltage. One end of the diodes would be connected to the signal and the other ends would be connected to +5 and -5 V respectively as seen below


---|----|------> signal | | D D | | | |



+5V -5V

The maximum current in the system is 2A. My question is: would this be an effective scheme and would this need multiple diodes for operation ?


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R

A series resistor for the signal might limit the current ...

Rene

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W

That entire class of parts is very fast, but has high capacitance, e.g., 120pF for the 39V diode, at 39V (more at 0V), did you consider that?

You have a "signal" that delivers 2 amps?

REng later wrote...

That's not the way we did it in the old days when I was an oceanographic instrument designer, following in the steps of the masters at WHOI. We used a pair of back-to-back diodes in series with the transducer output transformer, and obtained the receive signal across them. One side was grounded. If we were being careful, we took some additional precautions to be sure the transformer primary was shunted during the receive time, insuring all the signal appeared across the diode-protected input.

Thanks, - Win
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