Patent ID: 8724273

Claim:
A protective circuit comprising: a transient blocking unit comprising one or more blocking transistors having sources and drains connected in series with a parallel transistor subcircuit such that current passing through the transient blocking unit passes through the blocking transistors and through the parallel transistor subcircuit; wherein the parallel transistor subcircuit comprises two or more paralleled transistors having their sources and drains connected in parallel; wherein the transient blocking unit automatically transitions to two or more predetermined and distinct negative resistance states when a threshold current (I max ) is exceeded by an electrical transient; wherein the negative resistance states are predetermined by the paralleled transistors; and wherein the protective circuit has a DC current-voltage characteristic (I T (V T )) relating current through the transient blocking unit (I T ) to voltage applied to the transient blocking unit (V T ), wherein the characteristic has a current maximum at a trip point having a voltage V trip and current I max , wherein a first paralleled transistor begins to turn off at a voltage threshold of V trip , and wherein one or more second paralleled transistors begin to turn off at one or more voltages greater than V trip .