A circuit breaker comprising first and second JFETs, each comprising a gate, drain and source connection, the JFETs sources being operatively connected to each other to form a common-source connection and adapted to be connected to and operating to open an external circuit when the current flowing through the JFETs exceeds a predetermined threshold, the JFETs' gates, and common-source connection being operatively connected to a gate driver circuit which causes the JFETs to turn off when the predetermined threshold is exceeded; whereupon the current flows through the common-source connection into the second gate and into the gate driver circuit which causes the gate driver circuit to turn off the first and second JFETs and open the circuit breaker. Also claimed is a method of sensing an overloaded circuit comprising leading and trailing JFETs in a circuit that open the circuit and prevent current flow when a predetermined threshold is exceeded.