DIGITAL-TO-ANALOG CONVERTER USEFUL IN A TELEVISION RECEIVER

摘要

-19- RCA 72,373 A digital-to-analog converter for use in a television tuning system to convert bits stored in a register to a corresponding tuning voltage includes a counter for generating binary pulse signals having pulses with durations proportional to powers of 2 and a plurality of selection gates for selecting ones of the binary pulse signals in accordance with the states of respective bits stored in the register to generate a plurality of output pulse signals each having G pulses with durations proportional to where n is the number of the respective bit. The output pulse signals are justified with respect to each other by position-determining gates and combined to form G clusters of contiguous but non-overlapping pulses. The resulting pulse signal is filtered by a low/pass filter to derive the tuning voltage. G is selected as a compromise value consistent with both reasonable temperature stability and a reasonably fast filter response.