LOG114 for differential voltage input

Thread Starter


Joined Apr 6, 2009
Hi all,

I have just been introduced to LOG114[http://focus.ti.com/lit/ds/symlink/log114.pdf] and I am building a bioelectric signal amplifier. I am thinking of using the LOG114's A1,A2 and A3 as an instrumentation amplifier and the auxiliary op-amps A4 and A5 for filtering. But when I tried to modify the design for the above operation I am facing a lot of issues like frequency dependency over amplification and log conformity over change in frequency etc.

Has anyone tried using the LOG114 for such a use instead of the reference current input design ?

Thank you,


Last edited:


Joined Nov 30, 2010
Perhaps you could clarify your request. What I see is: Hi, I just met a new chip and I want to use it outside its specifications. Without telling you how far outside its specs, can anybody give me advice?

ps, specsheet attached


Ron H

Joined Apr 14, 2005
Aren't most bioelectric signals bipolar in nature, i.e., swinging both above and below ground? The LOG114 can only accept currents which are into the input pins.