[AD8232] Rigth Leg Drive amplifier

Hi T_yoshi ,

Good day. The effect of the integrator configuration on AD8232 depends on how you use the RLD and RLDFB pins. If the RLD pin is not used to drive an electrode as seen in Fig. 62 of the datasheet, the common-mode rejection will improve. If the RLD pin is used to drive an electrode as shown in Figure 64 of the datasheet, the system would be susceptible to common-mode interference.

Changing the 1nF capacitor to 10MΩ would greatly affect the loop gain for the frequency range of 50 Hz to 60 Hz for common-mode line rejection which is not advisable. Hope this helps.

Regards,
GIlbeys

Hi T_yoshi ,

Good day. The effect of the integrator configuration on AD8232 depends on how you use the RLD and RLDFB pins. If the RLD pin is not used to drive an electrode as seen in Fig. 62 of the datasheet, the common-mode rejection will improve. If the RLD pin is used to drive an electrode as shown in Figure 64 of the datasheet, the system would be susceptible to common-mode interference.

Changing the 1nF capacitor to 10MΩ would greatly affect the loop gain for the frequency range of 50 Hz to 60 Hz for common-mode line rejection which is not advisable. Hope this helps.

Regards,
GIlbeys

Hi Gllbeys,

Thank you for your reply.

I understand that changing the 1nF capacitor to 10MΩ  is not reccomended.

We are going to use RLD as the third electrode as in fig.64.

The datasheet says that the RLD improves CMRR by generating a voltage that is in antiphase with the input common mode voltage.

Since the RLD forms an integrator circuit, I believe that the output will be out of phase by 90 degrees with respect to the input common mode voltage.

Is this correct?

Does this mean that CMRR will be improved even if the deviation is 90°?

Best regards,

T-yoshi