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Right leg drive - Meaning & Implementation

What does right leg drive mean and how can it be implemented with AD8233?

  • Right leg drive (RLD) is a technique that uses an amplifier to reduce common mode interference when making bipotential measurements. There are many different types of signals that can be easily picked up by not just the human body but also the electrodes and cables. An example of such interference could be 50Hz/60Hz noise signals from the mains. Therefore when selecting an instrumentation amplifier for Biosignal measurements such as ECG or EMG it's important to select a device that has high common mode rejection ratio (CMRR). Take a look at this post on Engineer Zone for a little more insight on how this right leg drive technique works.  

    The AD8233 has an integrated RLD amplifier that senses the common mode voltage present at the input signal and can drive an opposing signal into the patient that is being monitored. Thus the driven electrode functionality maintains a constant voltage between the patient and the AD8233 greatly improving the common mode rejection ratio. The AD8233 customer evaluation board EVAL-AD8233 implements this and key information on the implementation can be found in the user guide for the AD8233