An input circuit for a field device for communication with bidirectional signals superposed on an analog signal, the input circuit being part of a current loop, supplies the field device with energy and simultaneously carries an analog current signal for prescribing a reference value. The field device is connected to an actuator that is suitable for achieving the reference value, and the input circuit has a voltage limiter, a shunt resistor and an inductance connected in series between its input and output. The input signal of an analog-to-digital converter can be taken at the shunt resistor. The voltage limiter is connected in parallel with a voltage regulator. The inductance is coupled via a capacitance to a reception unit and/or to a transmission unit for digital signals.
The invention relates to a device for generating a regulating signal for a direct voltage converter. The device has a voltage regulator and a current regulator at whose output the regulating signal can be tapped. Between the voltage regulator and the current regulator, a limiter is provided, which serves to limit the output signal of the voltage regulator. The limiter has an input connection which can be used to supply it with a predeterminable limit value signal for the current reference value.
