There are eight possible words which can be used to represent the
analogue input; the number of possible words with a word length of n
bits is 2". Thus we divide the maximum analogue voltage into eight parts
and one of the digital words corresponds to each. Each rise in the
analogue voltage of (1/8) of the maximum analogue input then results in
a further bit being generated. Thus for word 000 we have 0 V input. To
generate the next digital word of 001 the input has to rise to 1/8 of the
maximum voltage. To generate the next word of 010 the input has to rise
to 2/8 of the maximum voltage. Figure 1.40 illustrates this conversion of
the sampled and held input voltage to a digital output.