DIGITAL-TO-ANALOG CONVERTER (DAC) AND METHOD THAT PRODUCE AN APPROXIMATELY PIECEWISE LINEAR ANALOG WAVEFORM

摘要

A digital-to-analog converter (DAC), comprising: a plurality of waveform shaping circuits (100) that produce drive signals that switch during rise and fall times along rising (94) and falling (96) edges, respectively, between low and high plateaus (98) in response to waveform shaping circuits for a known clock period; a plurality of limiting switches (102) having transfer functions that limit the drive signals' low and high plateau values to low and high limiting values, respectively, while approximately maintaining the shape of the rising and falling edges; a weighting circuit (104) that weights the drive signals in accordance with their respecitve bits' positions in the codewords to produce weighted drive signals; and a summation circuit that sums the weighted drive signals to construct an analog waveform having output plateau values and rising and falling output edges, said waveform shaping circuits setting said rise and fall times so that the rising and falling output edges settle in rise and fall settling times Trs and Tfs, respectively, measured from successive clock edges of said digital signal to within a first error bound of a linear output ramp whose slope is a function of the difference between successive codewords, and said limiting switches setting the low and high limiting values so that the output plateau values settle in a settling time Tps measured from the end of said rise and fall times to within a second error bound of ideal values represented by the codewords so that the analog waveform more closely approximates a piecewise linear waveform, which has non-zero rise and fall times, than it does a zero-order-hold (ZOH) waveform to reduce spectral distortion in the analog waveform. 311 י" ג בתמוז התש" ס - July 16, 2000