VECTORLIST - The Mailing List For The Technical Discussion of Vector-Based Arcade Games

January_1998
Re: TVS as *input* clamping?


From: Anders Knudsen ( )
Date: Wed Jan 28 1998 - 18:07:18 CST


At 12:03 AM 1/29/98 GMT, you wrote:
>On Wed, 28 Jan 1998 15:09:30 -0800, Clay Cowgill < > wrote:
>
>>Dunno if anyone suggested this yet or not, but as I was staring at the
>>"input protection board" on a 314 deflection board in my vector monitor
>>during lunch...
>>
>>Couldn't you just use bidirectional TVS' (at, say... 10V for "X" and
>>8.2V for "Y") across ground and the inputs? So if an op-amp failed and
>>yanked the output the +/- rail the TVS would clamp it?
>
>Wouldn't that be the same as back to back zeners? I've seen that used
quite a
>bit as input clamps. Does the input daughter board on the Sega system
contain
>back to back zeners? Seems like it did.
>
>(Isn't a bidirectional TVS, internally, really just two zeners back to back?)

It is, however, there are physical differences in the manufacturing process
of a TVS vs a zener.
-Anders.

 -----------------------------------------
| Anders Knudsen
| ASIC Design Engineer
| Adaptec, Inc., Boulder Technology Center
|
| http://www.adaptec.com
 =========================================


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