Bio potential amplifier and its purpose

Bio potential amplifier and its purpose

Amplifiers are an important part of the modern instrumentation systems for measuring bio potentials. Such measurements involve voltages that are often at low levels,have high source impedances,or both. Amplifiers are required to increase signal strength while maintaining high fidelity. Amplifiers that have been designed specifically for this type of processing are known as “biopotential amplifiers.” The essential function of a biopotential amplifier is to take a weak electrical signal of biological origin( eg: brain)and increase its amplitude so that it can be further processed, recorded or displayed. The input circuit of a biopotential amplifier must also provide protection to the organism being studied. Any current or potential appearing across the amplifier input terminals is capable of affecting the biological potential being measured. (Here in our project we have considered the processing part of the above mentioned system ensuring that a good isolation is achieved between the patient part and the power supply part of the circuit.) In clinical systems electric currents produced by the bio potential amplifier and seen at its input terminals can result in microshocks or macroshocks in the patient being studied-a situation that can have grave consequences.To avoid these problems the amplifier should have isolation and protection circuitry, so that the current through the electrode circuit can be kept at safe levels and any artefact generated by such current can be minimized. The other basic requirements of the biopotential amplifiers are : 1) The output impedance of the amplifier must be low with respect to the load impedance and the amplifier must be capable of supplying the power required by the load. 2) Must operate in that portion of the frequency spectrum in which the biopotentials they amplify exists. 3) They make quick calibration possible. ` EEG requires an amplifier with a frequency response from 0.1H…


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