An isolation device having normally off detection is provided. The isolation device having normally off detection includes a transient blocking unit (TBU) having at least one depletion mode device disposed between a pair of sense terminals, and at least one normally off transition element disposed to drive a gate of the depletion mode device in the TBU, where the normally off transition element transitions from a first resistive state to a second resistive state and one depletion mode device is connected to one sense terminal, and the normally off transition element transitions by detection of a current through the TBU. The TBU can be unidirectional or bidirectional.