Abstract: Disclosed is a circuit for converting a current input of either polarity to a low voltage output of a single polarity. The circuit includes two pairs of pnp-npn transistors which are coupled to that current flow in one direction will turn on one pair while the other is reverse biased, and the same polarity will appear at the output regardless of the polarity of the input. The low voltage at the output is established by the voltage drop across the transistors of the pair which are conducting. The circuit is particularly suited for converting telephone line current to a voltage output of 1.5 volts or less.

Abstract: Disclosed is a monolithic oscillator circuit which relies upon the thermal characteristics of the semiconductor chip for oscillation. The circuit includes, in one embodiment, first and second transistors with similar output characteristics coupled to the input of a comparator element, and a third transistor coupled to the output of the comparator. The first and second transistors are unbalanced and the third transistor is placed close to only one of these transistors so that any heat generated will primarily affect the output of only the adjacent transistor. Thus, when a current flows from the comparator through the third transistor, the generated heat will decrease the potential across the first and second transistors until they are balanced, and the current through the comparator will shut off. The current remains off until the transistor cools off and an unbalanced condition is again achieved.

Abstract: Opto-isolators are disclosed which provide enhanced coupling between the light-emitting element and detector, and a method of manufacture is taught which permits efficient mass production of such devices. Recesses are etched in a silicon body and areas of the proper conductivity type are formed in the side walls to produce diodes, transistors or darlington pairs for light detection. Appropriate insulation and leads are then fabricated in the recesses to make contact to the detectors. In one embodiment, bonding pads are also formed at the bottom of the recesses along with associated conductors. Light emitting elements are then bonded to the pads on one major surface of the elements and wire bonded on the other major surfaces. The recesses are filled with an encapsulating material and the silicon body is etched apart to produce discrete devices.