Biological Amplifiers and Types of Biological AmplifiersPublished on 24/7/2018 and last updated on 3/9/2018
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Why is Bio Amplifier Required?Generally, biological/bioelectric signals have low amplitude and low frequency. Therefore, to increase the amplitude level of biosignals amplifiers are designed. The outputs from these amplifiers are used for further analysis and they appear as ECG, EMG, or any bioelectric waveforms. Such amplifiers are defined as Bio Amplifiers or Biomedical Amplifiers.
Basic Requirements for Biological Amplifiers
- The biological amplifier should have a high input impedance value. The range of value lies between 2 MΩ and 10 MΩ depending on the applications. Higher impedance value reduces distortion of the signal.
- When electrodes pick up biopotentials from the human body, the input circuit should be protected. Every bio-amplifier should consist of isolation and protection circuits, to prevent the patients from electrical shocks.
- Since the output of a bioelectric signal is in millivolts or microvolt range, the voltage gain value of the amplifier should be higher than 100dB.
- Throughout the entire bandwidth range, a constant gain should be maintained.
- A bio-amplifier should have a small output impedance.
- A good bio-amplifier should be free from drift and noise.
- Common Mode Rejection Ratio (CMRR) value of amplifier should be greater than 80dB to reduce the interference from common mode signal.
- The gain of the bio-amplifier should be calibrated for each measurement.
Types of Bio Amplifiers
- Differential Amplifier
- Operational Amplifier
- Instrumentation Amplifier
- Chopper Amplifier
- Isolation Amplifier