Author Topic: Replacing the MAX4239 with LTC6228 for higher bandwidth  (Read 161 times)

TristanR

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Replacing the MAX4239 with LTC6228 for higher bandwidth
« on: September 19, 2021, 12:22:57 PM »
Hi everyone,

I'm interested in buying the CurrentRanger, but would need a higher bandwidth than 300kHz. I'm thinking of replacing the two MAX4239 (GBWP: 6.5MHz) with the LTC6228 (GBWP: 890MHz). I'm not as concerned for the higher input offset voltage of the LTC6228 (20uV vs 2uV).

It seems that the LTC6228 can be a drop-in replacement for the MAX4239 (package/pinout, rail-to-rail, noise, shutdown feature). Is there anything else I should consider before doing this?

Thanks!

Felix

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Re: Replacing the MAX4239 with LTC6228 for higher bandwidth
« Reply #1 on: September 20, 2021, 08:44:05 AM »
I wonder what type of current signals you're trying to measure, that you need such fast opamps.
I haven't checked the specs on that opamp but note that all the noise figures get amplified 100 times ;-)
The combined cascading bandwidth is specified at -3db attenuation, so you may get higher bandwidth out of box, just more attenuated.
This type of change would only benefit the raw output since digital sampling cannot keep up with such fast signals you're trying to get.
I would just try it with the original opamps and then do the hack if you're up for it.
Also, definitely a at-your-own risk type of change, but I am interested in your progress and results.