Abstract: The present invention is directed to a buffer stage for buffering and isolating a signal source from an external load. The stage has a signal input terminal for receiving an input signal from said signal source and a signal output terminal for providing an output signal, corresponding to said input signal, to the external load. The stage comprises an input section including at least two driver transistors each arranged so as to operate with a predetermined bias current. The stage further comprises an output section including at least two output transistors each arranged so as to operate with a predetermined quiescent current, and a voltage source, coupled to the input and output sections and constructed and arranged so as to set the quiescent currents flowing through the output transistors substantially independent of the size of the bias current flowing through the driver transistors.

Abstract: A current sensor for detecting AC current through a load impedance of an electrical circuit. Sensor components are fabricated within a multilayer board so that a board can be made to comprise a plurality of independent sensors. The sensor includes a transformer circuit including a primary coil which is electrically coupled in series with the current path of the electrical circuit. This primary coil includes at least one current path element, in the form of a conductive strip constructed so as to add minimal resistance and inductance to the electrical circuit. The transformer secondary comprises at least a first electrically conductive coil inductively coupled to at least a part of the current path, and preferably a second electrically conductive coil inductively coupled to a second part of current path of the electrical circuit.