Custom Search

Friday, June 10, 2011

The A/D and D/A Converters as Functional Blocks

Fig 4.3 depicts the functional block representations of A/D and D/A converters. As indicated, the A/D converter (also called an ADC) accepts an analog sample VA and produces an N-bit digital word. Conversely, the D/A converter (also called a DAC) accepts an N-bit digital word and produces an analog sample. The output samples of the D/A converters are often fed to a sample-and-hold circuit. At the output of the S/H circuit a staircase waveform, such as that in Fig 4.4, is obtained. The staircase waveform can then be smoothed by a low-pass filter, giving rise to the smooth curve shown in the next figure. In this way an analog output signal is reconstructed. Finally, note that the quantization error of an A/D converter is equivalent to +/- 1/2 least significant bit (bs).

Converters Circuit Block

Fig 4.4 The analog samples at the output of a D/A converter are usually fed to a sample-and-hold circuit to obtain the staircase waveform shown. This waveform can then be filtered to obtain the smooth waveform. The time delay usually introduced by the filter is not shown.

Related Posts Plugin for WordPress, Blogger...