Abstract: In each character time of a pulse code modulation signal stream, the most significant bit group of the PCM character is reversibly incremented and decremented a plurality of times. The incrementing and decrementing is carried out in a selectable sequence for each discrete pair of subintervals in the character time. The selectable sequences are determined by the value of the least significant bit group of the character whereby the average value, over the character time of an analog signal derived from the changing most significant bit group information in each subinterval, is equal to the value represented by the character.

Abstract: A high-speed, low-power 1-bit adder includes a combination of current-mode switches connected in a dual tree configuration in series with respective constant current sources and summing resistors. Input operand signals select particular tree paths, thereby controlling the voltage appearing across the summing resistors and sum and carry output drivers responsive to these voltages.