DAC Ladder Networks
Anyone who has turned on a light switch has run a one bit digital to analog converter (DAC). When the switch is off, output is zero. When it's on, the full potential of the power system (battery or power grid) is applied to whatever is beyond the switch. With a multibit DAC, we throw switches, and some fraction of a reference potential or current is transmitted to the device output.
There are two common networks used in DACs: resistive ladders and capacitive ladders. We will deal mainly with the former; the latter are used mostly in high speed DACs whose low frequency performance isn't particularly important (an example would be a DAC in an audio device. People can't hear ultra-low frequencies, so an offset in the DC or low-frequency performance is irrelevant).