Surprisingly few Ghits fot this exact term, although plenty that seem to skirt around it.

I suspect FR more naturally phrases it in a different way...

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Note added at 8 hrs (2018-10-04 15:13:11 GMT)
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Further research reveals that this can sometimes be referred to as an 'amplificateur-tampon' (note that in EN too, it is properly 'buffer amplifier', but these days the 'amplifier' is almost always taken as red) — but this fails to make explicit the fact it is a 'current' one. Another term I've found is 'amplificateur séparateur' — but I think this would be misleading in Asker's context here, as to some extent 'séparateur' refers to the function it perfomrs — but only in some instances!

Another version I've found is '(amplificateur-)suiveur' — again, we do equally talk about a 'current follower' in EN, but the technicallly significant aspect of 'current' does need IMHO to be rendered in some way — after all, you can also have a voltage follower!

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Note added at 15 hrs (2018-10-04 22:19:50 GMT)
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@ BDF

Yes, 'buffer (amplifier)' is the full term, and both the terms you mention are used as translations of 'buffer' — in some context, the key concept of the 'buffering' role is 'to kkeep 2 things apart' — though in truth, that's not really the primary techical issue here, where it is more of a 'suiveur'.
But what is curious is that no-one in FR sems to mention the 'current' — it's true that in many applications, a buffer can be assumed to be buffering current — but NOT in ALL! The stated rôle here is to convert a voltage signal into a current one, which is what the function of a buffer is in some contexts. But I still think it amounts to dangerous under-translation if one simply leaves out the 'current' aspect.