Datasheet

Rev 03 Jan 2013 19:42 | Page 4
Figure 3. AD8232-CHARZ Board Simplified Schematic (Refer to Figure 12 for complete version)
Right-Leg Drive Amplifier
The integrated right-leg drive (RLD) amplifier senses the common mode voltage present at the signal
inputs and can drive an opposing signal into the patient. This driven electrode functionality maintains
the voltage between the patient and the AD8232 constant, greatly improving the common mode
rejection ratio.
The board configures the RLD amplifier as an integrator, formed by an internal 150kΩ resistor and an
external capacitor of 1nF (C1). This results in a loop gain of about 20 at line frequencies, with a
crossover frequency of about 1 kHz.
In a two-lead configuration, the RLD pin can be used to drive the bias current resistors on the inputs.
To create this connection, place a jumper on J3.