Analog Electronics for Measuring Systems

4Analog to Digital Converters

4.1. Digital to analog converters and analog to digital converters: an introduction

Computers and digital systems are wonderfully powerful when number-crunching tasks are required. Astonishingly, complex operations can be performed in the blink of an eye by cheap microcontrollers. A kid playing with a modern smartphone exploits a computing power and memory far greater than supercomputers employed for Apollo missions to the moon. Digital storage is cheap and compression algorithms have reached a tremendous efficiency. In other words, there is a clear convenience associated with the digital processing of signals.

Figure 4.1. Block diagram representation of analog to digital converter (ADC) and digital to analog converters (DAC)

Converters represent the link between the analog and digital worlds. An analog to digital converter (ADC) samples an input signal (i.e. takes snapshots of the voltage) and delivers a code on N bits, which digitally represents the sample. A digital to analog converter (DAC) performs the opposite function and converts a code into an analog voltage. Figure 4.1 shows the block diagram symbols, which are usually employed for an ADC and a DAC. In the case of an ADC, it has to perform the following activities:

• – the sampling, which consists of extracting a sample at a specific moment t₀ yielding an analog voltage that is held. ...