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This paper describes the development of a dc-powered Josephson logic family that uses hybrid unlatching flip-flop logic elements (Huffles). The Huffle circuit used in this study is modified by adding a parallel resistor to the original Hebard-type Huffle circuit. Analysis of the circuit's operation shows that the undesirable hung-up phenomena are prevented by this modification. Based on the result of the analysis, the circuit's parameters are derived and a typical operating margin of /spl plusmn/26% is obtained. Besides AND/OR operations using a threshold logic operation, two-input exclusive OR (XOR), two-input multiplexor (MUX), and three-input majority (MAJ) operations are realized using a Huffle gate in which 2-Josephson-interferometers (2JI) in the standard Huffle gate are replaced by stacked-2JI's. Thus, a Huffle logic family, formed from NOT, AND, OR, XOR, MUX, MAJ, and flip-flop (FF), are constructed. By using this Huffle logic family, a 6-b arithmetic logic operating unit (ALU), a 6-b analog-to-digital converter (ADC), and a 6-b gray-to-binary converter (GBC) have been successfully operated. During high-speed testing, a 1-b comparator was operated up to an input bandwidth of 6 GHz.