PCM signals D=A converter - has resistors arranged in R=2R chain resistor network to reduce residual voltages using MOSFETs

摘要

PCM digital signals with several bits are converted into analog signals in a circuit with longitudinal and transverse resistors of different value. The D/A converter has precision increased by reducing the effects of any residual differing gate source voltages and gate drain voltages on the MOSFETS whose source-drain paths form the resistors in its R-2R chain network. The MOSFETs (T11. T12 etc.) are connected in pairs in a specified manner to form one part of the R-2R network of resistors whilst the other part is formed by MOSFETs (T10, T20 etc.) connected in drain source series to form a string. The two MOSFETs in each pair are also in drain source series and their gates are connected to the same drive line.