ABSTRACT
In order to represent an analogue signal using digital codes it is necessary to approximate (or quantise) the signal into a set of discrete voltage levels as shown in Figure 3.2.
The 16 quantisation levels for a simple analogue to digital converter using a four-bit binary code are shown in Figure 3.3. Note that in order to accommodate analogue signals that have both positive and negative polarity we have used the two’s complement representation to indicate negative voltage levels. Thus, any voltage represented by a digital code in which the MSB is logic 1 will be negative. Figure 3.4 shows how a typical analogue signal would be quantised into voltage levels by sampling at regular intervals (t1, t, t, etc.).
