Patent ID: 7424322

Claim:
Evoked potential amplifying apparatus adapted to receive an evoked potential signal from sensing electrodes and a stimulus signal from a stimulator indicating when a stimulus pulse is applied, comprising: a first amplifier section having an input for receiving a signal from the evoked potential sensing electrodes and providing an amplified output; a second amplifier section receiving the output of the first amplifier section and providing an output signal, the output from the second amplifier section connected by a feedback loop to an input of the first amplifier section; a coupling capacitor connected to receive the output of the first amplifier section and connected in a feedback loop to an input of the second amplifier section; a controllable switch connected across the first amplifier section and receiving a switch control signal indicative of application of the stimulus pulse, the controllable switch closing when receiving the control signal to reduce the gain of the first amplifier section to nearly zero and thereby to reduce the overall gain of the amplifying apparatus; and a hold and delay circuit connected to the controllable switch to apply a control signal thereto and adapted to receive the stimulus signal from the stimulator.