R-2R Multiplexing Digital-To-Analog Converter
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
The R-2R digital-to-analog converter (DAC) uses multiplexing to connect the ladder output for each bit to all of the current sinks in sequence. A conventional R-2R DAC consists of an R-2R resistor ladder with a node for each input bit, a bit switch for each node and a current sink for each bit switch, as shown in Fig. 1. In such DACs, the DAC analog output does not always monotonically increase or decrease with corresponding increases or decreases in changes in the input bit values because of unequal current flow in the different current sinks connected to each bit. In the present design, a multiplexer driver switches each of the bits to each of the different current sinks in sequence so that the DAC analog output is an average current value. The operation of the DAC of the present design is explained by reference to Fig. 2.