Devices and methods for sensing physiological signals during stimulation therapy

Devices and methods provide for the sensing of physiological signals during stimulation therapy by preventing stimulation waveform artifacts from being passed through to the amplification of the sensed physiological signal. Thus, the sensing amplifier is not adversely affected by the stimulation waveform and can provide for successful sensing of physiological signals. A common mode voltage is applied to the stimulation electrodes while sensing during a recharge period where the common mode voltage approximates the stimulation pulse being received at the sensing electrodes. This common mode voltage is determined based on measuring a common mode signal for at least one of the inputs of the amplifier or by deriving the proper common mode from monitoring the output signal of the amplifier to observe the elimination of artifacts during stimulation. Blanking switches may be used to blank the sensing of the peak of the recharge period should that peak be relatively large.