A light bulb and a switch are examples of an analog circuit.

To be useful, A/D or D/A converters must have meaningful representation of the analog quantity and a digital representation and the digital quantity as an analog representation.

When the analog input to a tracking A/D converter is at a constant level, the digital output will oscillate.

The current across the MSB "rung" of a 4-bit R/2R ladder DAC if the reference voltage is 5 v and R is 8 is 625 A.

When the inputs of a four-bit D/A converter are connected to a binary up-counter, the output looks like an upward sloping line.