Intrinsic R2R resistance ladder digital to analog converter

摘要

An intrinsic R2R resistance ladder digital to analog converter (DAC) includes a plurality of matched semiconductor ladder switches, one in each of the R and 2R legs of the R2R ladder. The ON resistance of each semiconductor switch being matched to constitute the resistance ladder of the DAC; the ladder switches being operated in response to the digital signal input to the DAC; a reference circuit including a reference semiconductor switch matched with the ladder switches responsive to a reference current to generate a reference voltage; and a voltage follower circuit for monitoring the reference voltage and adjusting the current through the ladder switches to match the voltage at each ladder switch with the reference voltage for precisely fixing the DAC analog output current as a proportion of the reference current in dependence upon the operation of the ladder switches by the digital input signal.