A field device for use in monitoring or controlling an industrial process comprising: first and second loop terminals (146, 148) configured to couple to a two-wire process control loop; device circuitry configured to monitor a process variable or control a control device, the device circuitry powered by power from the two-wire process control loop; a current regulator in series with the first and second loop terminals (146, 148) and the device circuitry, the current regulator configured to regulate a loop current flowing through the two-wire process control loop and the first and second loop terminals (146, 148); a first shunt voltage regulator connected in series with the current regulator and the first and second loop terminals (146, 148), and in parallel with the device circuitry, the first shunt voltage regulator configured to regulate a first voltage across the device circuitry and to power the device circuitry, wherein the first shunt voltage regulator is coupled to the device circuitry which is configured to provide a voltage control signal for controlling the first voltage; supplemental circuitry connected in series with the first shunt voltage regulator and the second loop terminal, and powered by power from the two-wire process control loop shunted through the first shunt voltage regulator; and a second shunt voltage regulator connected in series with the first shunt voltage regulator and the second loop terminal, and in parallel with the supplemental circuitry, the second shunt voltage regulator configured to control a second voltage across the supplemental circuitry, and to power the supplemental circuitry through the second voltage. first and second loop terminals (146, 148) configured to couple to a two-wire process control loop; device circuitry configured to monitor a process variable or control a control device, the device circuitry powered by power from the two-wire process control loop; a current regulator in series with the first and second loop terminals (146, 148) and the device circuitry, the current regulator configured to regulate a loop current flowing through the two-wire process control loop and the first and second loop terminals (146, 148); a first shunt voltage regulator connected in series with the current regulator and the first and second loop terminals (146, 148), and in parallel with the device circuitry, the first shunt voltage regulator configured to regulate a first voltage across the device circuitry and to power the device circuitry, wherein the first shunt voltage regulator is coupled to the device circuitry which is configured to provide a voltage control signal for controlling the first voltage; supplemental circuitry connected in series with the first shunt voltage regulator and the second loop terminal, and powered by power from the two-wire process control loop shunted through the first shunt voltage regulator; and a second shunt voltage regulator connected in series with the first shunt voltage regulator and the second loop terminal, and in parallel with the supplemental circuitry, the second shunt voltage regulator configured to control a second voltage across the supplemental circuitry, and to power the supplemental circuitry through the second voltage.