Hi,
I have tried to use a INA116 Instrumentation amp as part of a potentiostat. I wanted to use the amplifier with a gain of 1 to provide a HIZ differential amp to measure voltage on a pair of electrodes. I wanted the ampl to have the capacity to take a +/-10V signal at 10Khz BW or so.
I have a pwr supply of +/-15V and am using a pair of opamps as per the app note to drive the input guards.
The ccts works well at DC, The guard ccts work well and impedance is indeed high.
My probelm is to do with distortion of the output at higher frq. The data sheet seems to indicat that the amp should work with a 10V output at more than 10K when on a gain of 1.
In practice however, I see a large amount of distortion when driving the input with a 10V pk sine at 10khz. The distrotion starts at about 3V pk at 3khz
The guard signals do not have the distortion and this indicates to me that the problem lies in slew rate limits on the instrumentation amp section.
When operating with a gain of 10 and using a 1V pk signal the cct performance is better but this is not good for my application.
Can anyone advise where i am going wrong?
I have tried a different chip on this cct as i thought the first one may have been damaged. so a second one from a different vendor was tried but it had the same results.
Because the guard ccts work i was thinking of using them to drive a external difference amp to get my output signal but this seams to be a bit silly.
