The invention relates to an autarkic field device or an autarkic radio adapter (2) for a field device (1), of automation technology fed with limited energy via an energy supply unit (3) associated, or associable, with the field device (1) or the radio adapter (2), characterized in that, between the energy supply unit (3) and an internal voltage source (4), whose voltage exceeds, or at times can exceed, the voltage of the energy supply unit (3), a barrier (5a; 5b) of at least one diode group having at least two diodes (6) connected in parallel is arranged, which blocks flow of electrical current from the internal voltage source (4) to the energy supply unit (3) or to the connection terminals (7) of the field device (1) or of the radio adapter (2) for the energy supply unit (3).