In general, signals resulting from physiological have very small amplitudes and must therefore be amplified their processing and display can be accomplished. The specifications and lists of characteristics of biopotential amplifiers can be as long and confusing as those any other amplifier. However, most typical medical applications, the most relevant amplifier characterizing parameters are the seven described below;
Gain= The signals resulting from electrophysiological activity usually have amplitudes on the order of a few microvolts to a few milivolts. The voltage of such signals must be amplified to levels suitable for driving display and recording equipment.
Frequency Response= The frequency bandwidth of a biopotential amplifier should be such as to amplifier, without attenuation, all frequencies present in the electrophysiological of interests.
CMRR= The human body is a good conductor and thus will act as an antenna to pick up electromagnetic radiation present in the environment. In addition other spectral components added by fluorescent lighting, electrical machinery, computers and so on. The resulting interference on a signal ended bioelectrode is so large that it often obscures. The underlying electrophysiological signals.
Noise and Drift= This parameters are additional unwanted signals that contaminated a bio potential signal under measurement are generated within the amplifier circuitry.
Recovery= The time required for the return of normal operational conditions of the biopotential amplifier after the and of the saturating stimulus is known as recover time.
Input Impedance= The input impedance of a biopotential amplifiers must be sufficiently high so as not to attenuate considerably the electrophysiological signal under measurement.
Electrode polarization= Electrodes are usually made of metal and are in contact with an electrolyte, which may be electrode paste or simply perspiration under the electrode.
