Digital to analog converter
In electronics, a digital to analog converter (abbreviated to DAC or D-to-A) is a device for converting a digital (usually binary) code to an analogue signal (usually a current or voltage). This is done with a network of resistors, usually a ladder of two sizes of resistors, one twice the other.
An analog to digital converter performs the reverse operation.
An analogue signal from a microphone or other sound source can be converted to digital form for storage in a computer, where it can be edited if necessary and then reconstructed for playback. In a personal computer, the conversion is usually done in a sound card, but there are some USB devices that do this conversion externally to improve the sound quality.
Video signals from a digital source, such as a computer, must be converted to analog form if they are to be displayed on an analog monitor. As of 2003, analog monitors are more common than digital, but this may change as flat panel displays become more widespread. The DAC is usually integrated with some memory (RAM), which contains conversion tables for gamma correction, contrast and brightness, to make a device called a RAMDAC.
DACs are used in analogue signal processing circuits to replace potentiometers. They allow small adjustments to be made to the circuit by software, instead of the old technique of using a screwdriver. Because this type of DAC is updated only infrequently, it often has a slow serial interface. Some types have non-volatile memory to enable them to remember their last settings when the power is switched off.