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Protecting my Analog output card

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archiees

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hi guys,
I have an Analog output card which is generating +/- 10 volt, and drives a metal plate in my instrument. This metal plate which is basically a load capacitor of around 20 pF, can sometimes have transient voltage from pick up. I want to protect my AO signal channels from these high transient voltages which can essentially fry my AO card. Can i use an opamp as a voltage follower before feeding this analog signal. So if by chance there are these surges my opamp (2 bucks) is fried not my card which is like $2000.
The type of analog waveforms fed are fairly simple such as ramps, triangular etc and change with less than usec time period.
Please help.
 

archiees,

If your output signals are not very fast, you could try a transorb on the Analog card output.
Regards,
Kral
 

    archiees

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Opamp as buffer will be good option but it has to be supported by bidirectional transient voltage suppresor (1.5KE15A , SA12A , or similar) or two 10V zener diodes connected in series anode-to-anode (≈11V +/- protection) ..
Regards,
IanP
 

    archiees

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thanks guys very useful information for me.
Though, one more question, i found these Channel protector lying in my lab.
https://www.analog.com/en/prod/0,2877,ADG467,00.html
Can i use these in series with my signal wires? The good thing is in one package i can have 8 channels protected.
Though it says over voltage protection upto 40 volts. So if i have a high surge, say 1 KV, will it still prevent the damage to my Analog output card? I don't care if its only the channel protector chip which is fried, as i can replace them inexpensively.
 

Using this IC helps but does not solve pin protection in 100% ..
See picture below for complete protection of AD/DA inputs/outputs ..
You need to use TVSs (or 2 zener diodes / pin) ..
Regards,
IanP
 

    archiees

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