TODAY’S PATENT – DIGITAL CIRCUIT
This invention “Digital circuit” was invented by Franklin T. Clark, Jr. and assigned to Tantera Inc, was granted patent on 10th May, 1977 by the USPTO bearing patent grant number USRE29217E to the patentee. The subject of the present invention is a digital circuit, such as a pulse regenerating circuit or logical circuit, including a signal memory function. Current switching is frequently the foundation of a high-speed digital circuit with memory capabilities. Because the emitters of the two transistors in the current switching circuit are connected to one another, differential operation is possible even when the transistors are unsaturated, allowing for high-speed operation.
Transistors with an unsaturated operating state are used in the digital circuit of the present invention. There are two differential connections between each pair of first and second transistors. At the bases of the first transistors, the second transistors’ collectors are coupled. To create a positive feedback loop, the bases of the second transistors are connected to at least one first transistor’s collector. The first and second transistors in a preferred configuration are PNP transistors and NPN transistors, respectively. To the emitters of the first and second transistors, respectively, are linked first and second current sources. Two resistors connect the bases of the first transistors to a first terminal for supplying a steady voltage. The bases of the second transistors are also linked via a pair of resistors to a second terminal for supplying a steady voltage. A control signal applied to the bases of one pair of transistors causes the circuit to change state.