| 摘要 |
Differential heating is avoided by a digital to analog converter for generating analog cyclical waveforms having a period. The cyclical waveforms are generated by conversion of a sequence of step wise linearly incrementing digital phase words presented during the period for conversion. The digital to analog converter has a clock 620 for operating conversion timing within the digital to analog converter. The clock 620 generates a clock pulse for conversion of each of the digital phase words by said digital to analog converter while generating the cyclical waveform. A lookup read only memory 606 for converting each of the incrementing digital phase words within the period into a plurality of ON commands to be used by a plurality of current sources 612. The plurality of ON commands are timed to generate the cyclical waveforms and have nearly equal time duration approximating a 50 percent duty cycle. A first exclusive - OR 608 circuit has a first input, a second input and an output. The first input is connected to the sequence of ON commands generated from the lookup table. The sequence of ON commands is generated using a second exclusive OR circuit 618 and a unary decoder 610. A buffer 612 stores the output from the first exclusive - OR circuit for the duration of each clock cycle. The buffer drives the current sources thereby activating each of the current sources for nearly equal time intervals during the period. A summer 614 sums the current sources into a sum of currents. A current to voltage converter converts the sum of currents into an output voltage, the output voltage generating the cyclical waveform. The cyclical waveform has one or more non-linear portions reflected in the content of the read only memory 606. |
