Electromedical apparatus

Abstract

Known current stimulation apparatus have a current waveform generator with a constant-current output stage, which operates with a relatively high operating voltage (up to several 100 Volts), in order that the necessary currents can be applied even in the case of extremely high patient resistances. In the application of large-surface electrodes, the load resistances are generally comparatively low. The operating voltage required for the necessary currents for such normal instances is here substantially lower than the high operating voltage actually available, which leads to unpleasant irritation phenomena due to an increase in the current density when the resistance is suddenly altered due to the separation of the electrodes or the like. In accordance with the illustrated embodiment, the constant-current stage and the operating voltage supply are connected to an operating voltage control circuit which, in dependence upon the load resistance and/or the current intensity, regulates the operating voltage (U.sub.B) for the constant current stage from an initial voltage value (U.sub.V) to higher values with an increasing load resistance, whereby, however, the control time constant is such that, in the case of a differential resistance change which exceeds a specifiable threshold, the change in the operating voltage proceeds less rapidly than the resistance change. In the case of rapid change, for example, due to the separation and falling-off of electrodes, the operating voltage is thus only slowly adjusted upwardly such that undesired irritation pheomena are prevented.