Sunday, 16 July 2017

Bioelectric Amplifiers

As the name implies, the bioelectric amplifiers are used to amplify the bioelectric signals. The bioelectric signals measured from various body parts are having an amplitude ranging from mVs to ┬ÁVs. So it is necessary to amplify the extremely low amplitude signals for the analysis of the biological data. It is for this purpose that the bioelectric amplifiers are used. Usually we use operational amplifiers as bioelectric amplifiers due to its high gain and other versatile features.
The bioelectric amplifiers have some properties.

1. The gain of the bioelectric amplifier may be low, medium or high depending on the type of amplifier and the signal to be amplified. For example the low gain amplifiers are used for the measurement of action potential, medium gain amplifiers are used for the amplification of ECG waveform and the high gain amplifiers are used for EEG signal amplification.

2. The bioelectric amplifiers may be ac coupled or dc coupled.

3. The frequency response of a bioelectric amplifier range from very low frequency to high frequency range.

4. Bioelectric amplifiers have differential input and single ended output.

5. High CMRR and extremely high input impedance.

Two important parameters of bioelectric amplifiers are noise and drift. We have to avoid the effect of both these parameters on bioelectric amplifiers. Drift is the change in output due to the change in temperature. Noise is the thermal noise generated in electronic devices. Both these problems can be avoided by proper design to make the bioelectric amplifier more effective.

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