Current-summing digital-to-analog converter with binarily weighted

Abstract

A digital-to-analog converter has a bias block that provides first and second voltage outputs, and a bit cell having a switch for selectively connecting either a first or a second summing node to a current flow path depending upon the state of a binary input signal. An output bipolar transistor and a current source are connected in series between a supply voltage and a reference potential. A first MOS transistor is connected in the current flow path with its gate connected to the bipolar transistor. A base current compensating second MOS transistor is connected between the supply voltage and a base of the output bipolar transistor with its gate connected to the first voltage output of the amplifier. A resistor is connected between the base of the output bipolar transistor and the second voltage output of the amplifier. When a plurality of bit stages are provided, the resistor of each of the plurality of bit cells is sized according to a position of its associated cell in the bit order. The resistors may be sized as a power of 2 according to a position of its associated cell in the bit order, or, except for a most significant bit cell may be sized 2 times larger than the resistor of the most significant bit cell, with a plurality of equally sized resistors connecting adjacent bit cells in an R-2R network.