Many organs in the human body manifest their functions through electric
activities. Measurements of these and other biopotentials can provide vital clues
that permits study as real functions of the organs. These measurements are not
an easy task because envolves extremely low amplitudes data acquisition,
between 1 μV and 10 mV, and also because these bioelectric recordings are
often disturbed by an excessive level of interference presents, resulting in
signal/noise degradation. Therefore, the biopotential amplifier project must be
associated with precaution to final circuit can meet great characteristics in such
signals measureming. This work shows a study about biopotentials origins, their
characteristics, circuits used in signal amplifiering and filtering, interferences
present in measurement systems and some circuits used to reduce such
interferences. Thereafter, is developed a cortical biopotential amplifier with
filtering and gain blocks. The tests with amplifier where realized by registering a
visual evoked potential and the electroencephalogram. In the experimental
results is possible to observe a satisfactory equipment performance.
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