Protecting my Analog output card

[archiees]

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.

 

[Kral]

archiees,

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

 

[IanP]

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]

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.

 

[IanP]

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