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AD8397 to convert NI Current Driver from 20mA to 40mA?

Question asked by andy_3141593 on Dec 28, 2016
Latest reply on Dec 28, 2016 by JinoL

Hi There,

 

Well, its time to get out the old circuit design books!  Its been a while for me. Situation: I purchased a National Instruments PXI-6704 card with 16 analog current driver outputs. See link below. NI tells me that the current drivers regulate current by controlling voltage (as opposed to a switching strategy). The channels output from 4mA to 20mA. Problem: I need a driver rated for 40mA.  NI does have other cards that can be stacked to achieve 40ma, but I need at least 14 channels, and that gets out of my cost constraints.

 

Here's my thoughts so far: I think I'm looking for a "current amplifier"... i.e. current in, current out, current gain, current controlled current source CCCS. This is for instrumentation, so I believe that I need an amplifier with good linearity and noise rejection. My first thought was to use an operational amplifier to achieve linearity.  It looked like AD8397 might handle the current load and I'll probably have 24V and ground to supply it in the configuration below. I've not designed circuits in a long time, so I'm just starting to feel my way around. I thought that I'd try to make a few contacts to get help along the way.  I googled my way to Analog Devices looking for a high current OpAmp and saw your EngineerZone. I've not sure about the power supply and haven't even thought about I/O protection.  NI warned me to be careful not to overload current driver from the 6704 card rated for +-10V with voltage.

 

I've not designed circuits in a long time, so I'm just starting to feel my way around. I thought that I'd try to make a few contacts to secure some help for the journey. I googled my way to Analog Devices looking for a high current OpAmp and saw your EngineerZone. I wiki'd my way from SPICE to ADIsimPE.

 

So, my questions is, am I talking to the right people, am I on the right track, do you have any suggestions?  Thank you!

 

Andy

 

PXI-6704 NI PCI-6704 - National Instruments 

Circuit Op-Amp Current Amplifier - YouTube 

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