Improved Howland current source

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Majjik

Joined Oct 17, 2013
1
Hi guys,
I need your help a little bit :) Is here anybody who could help me with design - improved howland current source? I need constant current approximately 500uA with 50kHz and the input signal will be 0.5V. I created some source but the problem is that when I use OP177 and I change kHz or R_load the output current have changed, but when I use OPA277 nothing happen and the I(rms) is 491uA.

Why OP177 does not want to work?

Thank you very much
 

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crutschow

Joined Mar 14, 2008
24,352
Both of those op amps should work but you may have problems at 50kHz due to their low gain-bandwidth. Does the OPA277 work with a low frequency or DC input?
 
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