Abstract: A pulsed light signal receiver comprises a photo-sensitive transistor having a base and a collector and an emitter; a load resistance in the collector circuit and a constant current device in the emitter circuit. A capacitor shunting the constant current device over a predetermined range of signal frequencies renders the transistor gain high for such frequencies. The constant current device may be a field effect transistor with its gate at ground potential and a resistance in the source to ground circuit selected to determine the idling current of the FET and provide thermal stability for the photo-transistor circuit. A low impedance, balanced-to-neutral, output is provided.

Abstract: A self-balancing D.C.-substitution R.F. power measuring system includes ft and second high gain differential operational amplifiers, a bolometer element, and a reference resistor element. The amplifiers and the two elements are connected in a current loop with one of the elements connected between the output terminals from the differential amplifiers and the other of the elements connected between center points of isolated dual power supplies associated with each of the amplifiers. The inputs to one amplifier are connected from an adjacent end of one of the elements and the far end of the other element, while the inputs to the second amplifier are connected to the far end of the one element and the adjacent end of the other element. Current flows out of one amplifier and into the other.