Driven right leg circuit

A Driven Right Leg Circuit or “DRL” circuit is an electric circuit that is often added to biological signal amplifiers to reduce Common-mode interference. Biological signal amplifiers such as EKG (Electrocardiogram) EEG (Electroencephalogram) or EMG circuits measure very small electrical signals emitted by the body, often as small as several micro-volts (millionths of a volt). Unfortunately, the patient's body can also act as an antenna which picks up electromagnetic interference, especially 50/60 Hz noise from electrical power lines. This interference can obscure the biological signals, making them very hard to measure. Right Leg Driver circuitry is used to eliminate interference noise by actively canceling the interference.

Other methods of noise control include:

• Faraday cage
• Twisting Wires
• High Gain Instrumentation Amplifier
• Filtering

Further reading

IEEE Citation format (ISBN added)
[1] J.G. Webster, "Medical Instrumentation", 3rd ed, New York: John Wiley & Sons, 1998, ISBN 0-471-15368-0.
[2] B. B. Winter and J. G. Webster, “Driven-right-leg circuit design,” IEEE Trans. Biomed. Eng., vol. BME-30, no. 1, pp. 62–66, Jan. 1983.