Embodiments of the present invention may provide string DAC architecture with multiple stages for efficient resolution extension. A first stage may include an impedance string (e.g., resistor string). A second stage may include a switch network with each switch having more than two states (impedance values). A third stage may include a string DAC with an impedance string with a set of corresponding switches. In multi-channel embodiments, multiple second and third stages may be provided for each channel while sharing the same first stage (i.e., impedance string). Each second stage switch networks may be controlled based on the relationship between the different channels such as MSB values. Thus, the second stage switch networks may provide different impedance values to compensate for loading effects in multi-channel, multi-stage string DAC designs.