7.1 Introduction

The processing of analogue electrical signals and digital data from one form to another is fundamental to many electronic circuits and systems. Both analogue (voltage and current) signals and digital (logic value) data can be processed by many types of circuits, and the task of finding the right design is a sometimes confusing but normal part of the design process. It depends on identifying the benefits and limitations of the possible implementations to select the most appropriate solution for the particular scenario. Initial concerns are:

• Is the input analogue or digital?

• Is the output analogue or digital?

• Will signal processing use analogue or digital techniques?

This idea is shown in Figure 7.1, where signal processing uses either an analogue signal processor (ASP) or a digital signal processor (DSP). If an analogue signal is to be processed or output as digital data, then the analogue signal must be converted to digital using the analogue-to-digital converter (ADC). The operation of this circuit is discussed in Chapter 8. If a digital signal is to be processed or output as an analogue signal, then the digital data will be converted to analogue using the digital-to-analogue converter (DAC). The operation of this circuit is also discussed in Chapter 8.

Figure 7.1: Processing of analogue signals and digital data

ASP and DSP each has its own advantages and disadvantages:

Analogue implementation:

Advantages:

• high bandwidth (from DC up to high signal frequencies)

• high resolution

• ease of design

• good approach for simpler design solutions

Disadvantages:

• component...