A digital-to-analog converter (DAC) is an electronic component whose function is to transform a digital value (encoded on several bits) into an analog value proportional to the encoded digital value. A digital-to-analog converter is an elementary components of almost all devices of digital consumer electronics (e.g. music players) and communication technology (e.g. smartphones). Typically, the DAC is designed as an integrated circuit (IC).
There are several solutions to create an analog signal from a digital system. It is divided into two categories, those with pseudo-analog output (the output signal contains the analog message, but other signals are added to it) or analog output. In the latter case, resistor network converters are usually used. DACs are widely used in audio equipment such as digital music players, speakers, audio amplifiers, mixing consoles, to convert digital audio signals into analog signals that can be heard by our ears.
An analog-to-digital converter generates a stepped signal from a continuous set of values. A digital-to-analog converter cannot generate a continuous signal from the staged signal. Once the gradation has occurred in steps of 1 LSB (least significant bit), it cannot be undone. In the case of a sequence of variable values, however, the gradation is ground down by necessary filtering.
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A digital signal is a discrete-time and discrete-value signal, as shown in the adjacent figure. The digital-to-analog converter converts the quantized information, which is available as binary information, into a signal that can be continuously provided to an analog device.
An approximation to a continuous original signal, on which a digital signal can be based, is achieved with a reconstruction filter, usually directly following the digital-to-analog converter. This is of great importance in audio technology, for example.
The principle of pulse width modulation is to create a clock signal whose duty cycle is variable and proportional to the coded value. If the average of this signal is extracted (by means of a low-pass filter), an analogue value proportional to this duty cycle is obtained.
The analog conversion to resistor network or resistance scale is based on the principle of voltage division (divider bridge for the unary network) or current division (R/2R network). In all cases, an impedance matching stage follows the resistive mounting so that an output load does not interfere with the conversion.
A low-pass filter is a filter that allows low frequencies to pass through and attenuates high frequencies, i.e. frequencies above the cut-off frequency. It could also be called a high-cut filter. The low-pass filter is the inverse of the high-pass filter and these two filters combined form a bandpass filter. The concept of a low-pass filter is a mathematical transformation applied to data (a signal). The implementation of a low-pass filter can be done digitally or with electronic components.
