A stimulating medical device, comprising a plurality of electrodes, and a current source and a current sink connected to each one of the electrodes. The medical device also comprises a calibration arrangement configured to compare the current provided by a selected one of the current sources to the current sunk by a selected one of the current sinks, and configured to adjust an operational parameter of at least one of the source and sink based on said comparison such that the current provided by the selected current source is substantially the same as the current sunk by the current sink.
