Modulator switching system having at least one semiconductor switch for adaptation to different load ranges and protection thresholds

A modular switching system includes a transistor operative in a switching mode for applying current to a load. Adaptation of the system to accommodate different values of load is attained by coupling an input drive ,signal to a base terminal of the transistor via a variable gain amplifier wherein the gain is established by a load-adaption signal to meet the requisite base current drive signal for the load. Plural emitter terminals of the transistor connected to separate branches of a monitoring circuit, each branch having its own threshold detector, for monitoring of minimum and maximum values of load current.