Field-device
electronics including an
electric current adjuster, through which a
supply current flows. The
electric current adjuster adjusts and / or modulates the
supply current. The
supply current is driven by a supply
voltage provided by the
external energy supply. Additionally, the field-device
electronics has an internal operating and evaluating circuit for controlling the
field device, as well as an internal supply circuit
lying at a field-device
electronics, internal input
voltage derived from the supply
voltage and feeding the internal operating and evaluating circuit. Provided in the supply circuit is a useful-
voltage controller flowed-through, at least at times, by a first component of the supply current. The useful-
voltage controller provides in the field-device electronics a first internal, useful voltage controlled to be essentially constant at a predetermined, first voltage level. Moreover, the supply circuit has a second useful-
voltage controller flowed through, at least at times, by a second current component of the supply current. The second voltage controller provides in the field-device electronics a second internal, useful voltage, which is variable over a predetermined
voltage range. Also contained in the supply circuit is a voltage adjuster flowed-through, at least at times, by a third current component of the supply current. The voltage adjuster serves to set and maintain the internal input voltage of the field-device electronics at a predetermined voltage level. In accordance with the invention, the operating and evaluating circuit is flowed-through, at least at times, both by a first useful current driven by the first useful voltage, and by a second useful current driven by the second useful voltage.