An electric current controller for field-device electronics controls
and/or modulates the supply current. The supply current is driven by a
supply voltage provided by an external energy supply. The field-device
electronics has an internal operating and evaluating circuit for
controlling the field device, as well as an internal supply circuit, the
internal input voltage being derived from the supply voltage for feeding
the internal operating and evaluating circuit. In the supply circuit is a
voltage controller flowed-through, at least at times, by a first
component of the supply current. The 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 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.