Can driven-right-leg circuits increase interference in ECG amplifiers?

Abstract

The Driven-Right-Leg (DRL) circuit has been used for about 50 years to reduce interference due to common-mode voltage in biopotential amplifiers in scenarios that range from fixed equipment supplied from power lines to battery-supplied ambulatory monitors, and for systems that use gelled, dry, textile, and capacitive electrodes. However, power-line interference models predict that for isolation amplifiers, currently mandated by safety standards, power-line interference can often couple mostly in differential mode rather than in common mode. In this work we analyze the effect of the DRL circuit in different ECG leads to elucidate its actual effect on power-line interference reduction. It turns out that that the DRL circuit, which effectively reduces common-mode interference, affects differential-mode interference in an unpredictable way and can increase interference.

NeuroMonitor: a low‐power, wireless, wearable EEG device with DRL‐less AFE

“…The device was configured for two channel referential montage with online mode. PSD of Alpha (8-13 Hz), Beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and Theta (4-8 Hz) rhythms from FP2 location are plotted in Fig. 8 for four subjects (denoted with different colours).…”

“…3 of [25]). In addition, DRL circuit might increase differential mode noise if not properly matched, which is a severe design barrier for modular and scalable EEG systems [18]. Nonetheless, DRL based design even for battery operated EEG systems are still utilised [6, 10–12, 14].…”

“…This DRL circuit design constrains modularity and scalability for EEG channels due to interdependency of channels, as the number of channels of the system needs to be fixed at the design time for optimal operation. In fact, DRL circuit might increase differential mode noise if not properly matched [18]. This restricts the number of channels for the EEG system at deployment time.…”

An Engineering Perspective of External Cardiac Loop Recorder: A Systematic Review

“…The most widely used IA ICs were developed by Texas Instruments and Analog Devices. Texas Instruments ICs INA116 [109, 110], INA121 [111], and INA128 [112] were most widely used in ECG signal acquisition systems. INA116 provided high input impedance (1015 Ω) and the bandwidth of 0.38–44 Hz (±5%) with a single supply of 2 V; it was used for long time ECG monitoring of athletes [109].…”

“…It was also used in the designing of low noise EEG/ECG sensor circuit [110]. INA121 with a two-input voltage buffer as driving Right Leg (RL) circuit provided differential gain = 1000 from 0.05 Hz–100 Hz and common-mode gain = 0.06 at power-line frequency (50 Hz) that results in CMRR = 86 dB [111]. Analog devices ICs AD620 [113] and AD623 [114] were used for ECG signal acquisition and monitoring.…”