| 摘要 |
A digital-to-analog converter suitable for use in a television tuning system for converting bits of a digital word to a corresponding tuning voltage includes a first digital-to-duty factor converter responsive to a group of the most significant bits of the digital word for generating a first incrementally variable duty factor pulse signal and a second digital-to-duty factor converter responsive to a group of the next most significant bits of the digital word for generating a second incrementally variable duty factor pulse signal. The amplitude of the first and second pulse signals are differentially weighted, e.g., by standard tolerance resistors (+/-10%), such that the maximum average DC potential of the second signal is greater than a single increment of the average DC potential of the first signal. The weighted signals are combined and filtered by a lowpass filter which derives the tuning voltage. This deliberately results in non-monotonicity but without a significant reduction in resolution. |
