A multiple-stage digitally-switched impedance has one "type B" stage and at least
two "type A" stages. The type A stages are cascaded between high and low reference
nodes and the type B stage. Each stage comprises a string of series-connected impedances
and a switch network. A decoder responds to an digital input signal by controlling
the switch networks to switch selectable portions of the strings in the type A
stages into a series connection with the type B stage's string, and to control
the type B stage's switch network to tap its string at a location to provide a
impedance corresponding to the n-bit digital input signal between the final output
node and at least one of the high and low reference nodes. Each stage provides
a portion of the impedance's n-bit resolution, and the sum of the bits of resolution
provided by each stage equals the total n-bit resolution.
