Digital-to-analog converter

A digital-to-analog converter comprising input circuit connections (861, 862, 761, 762) for receiving a plurality of binary input signals, and means responsive to the binary input signals for producing an analog output signal at an output circuit connection (1001), the magnitude of the analog output signal being representative of the binary input signals, characterized in that:

• the converter includes a constant current generator (1004, 1018-1022) connected to a power source, the constant current generator comprising a current mirror with a first transistor (1018) and a second transistor (1004) and wherein a fixed constant current in the first transistor is repeated in the second transistor;
• the means for producing the analog output signal is comprised of means for subtracting a source current reflective of the binary input signals from the current in the second transistor at a first current summer (1003), the amount subtracted being determined by the received binary input signals;
• and
• the converter provides a constant total current demand from the power source while receiving any one or combination of the plurality of binary input signals.