An electrical circuit having a load that includes at least one semiconductor junction device supplied with operating current at a voltage sufficient to bias the semiconductor junction device into conduction and control means to provide or inhibit supply of power to said load. A protection arrangement for the electrical circuit includes a sensing circuit that detects characteristics of the load when the operating current is not flowing. The sensing circuit includes threshold comparison circuit that compares the sensed voltage level with at least one stored value representative of a threshold of a load characteristic indicative of a correctly functioning semiconductor junction device. The sensing circuit includes a sensing current generator which in the absence of operating current to the load effects passage through the load of a sensing current having a value that is less, for a semiconductor junction, than the forward conduction threshold thereof.