Computer Interfacing

Conversion between digital and analogue

conversion process takes a finite length of time. While

this conversion is taking place the signal may well be

varying in amplitude. It is hardly reasonable to ask the

converter to digitise a sample at a specific instant of time

then to change that value during conversion! The answer

is to freeze the sample prior to conversion, this process

taking negligible time compared with the conversion time

that follows. Then the converter does its job and pro-

duces the digitised sample, after which the analogue

sample is released and a new sample frozen. The reason

for calling the circuit that performs this vita ...