Active Electrodes are electrodes that have a build-in amplifier. This helps to reduce noise from the cables and produces better signal quality. In addition less skin preparation is needed when using active electrodes. Also see Passive Electrodes.
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Details
I see that
Jim Peters
(no board, gold-plated “headers”)
and
Jarek (no board, flat silver plates)
and
Pedro Ortega (circular breadboard, silver pins)
are using the
TLC272CP dual op amp
in their active electrodes.
Joe Street
seems to be using the
TL061CDR
A brief look at those links makes me think that the TLC272 (dual op amp) is slightly better than the TL062 (dual op amp) or the TL061 (single op amp, a few pennies cheaper).