# DAC Ladder Networks

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How can we understand ladders? A step at a time. In all cases, we'll have some reference voltage V_{ref} that is the full scale range of the DAC. For purposes of this section, presume that the DAC encodes straight binary from 0 to V_{ref}. Other coding schemes aren't hard to understand once this first one is clear.

The first circuit to consider is a simple voltage divider. For two equal resistors, we have 3 points we can monitor: zero, the mid-point of the resistive ladder (where V = V_{in}/2), and the top of the ladder (where V = V_{in}). If we had an electronic switch, we could choose among 3 outputs. Clearly, given N resistors, we can select among N+1 outputs.