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AD8212 with 850V common mode voltage

Question asked by LeTriColor on Feb 14, 2014
Latest reply on Aug 13, 2017 by Lorentz

Hello,

 

  I was looking for a current sense amplifier with a high common mode voltage and I saw your circuit from the lab CN0218 which showed how you can achieve more than 500V of common mode voltage with the AD8212.  In my design I have a source that is ~850V common and i think that this circuit would still work but i need to change the transistor Q1.  I have looked through several different suppliers of transistors and i cannot seem to find a PNP transistor with more than -600V Vbe.  Can you let me know two things:

 

1. Can you recommend a PNP device that can handle up to 850V common mode voltage?  I have been unsuccessful in finding one. 

 

2. Can i use two PNP devices at -500V in series instead?  The picture below illustrates what i would like to see if possible if there isn't a feasible transistor from 1. (i took an snapshot from CN0218)

 

AD8212_850V.jpg

 

Thanks for your support!

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