Mehmet Can ÇAPAR 030070131, 6th week definitions (PART 3)

Digital-to-Analog Converters


(old answer) (better))
Analog-to-Digital and Digital-to-Analog Converters
Most sensors transmit data in analog form. At some point this must be converted to a digital format to allow the computer to read it. This is done by means of an analog-to-digital converter. Conversely, the driver circuits of actuators require analog input. Thus, the digital output of the computer must be converted to an analog signal by a digital-toanalog converter. Transmission of an analog signal requires only a wire pair, often in the form of a coaxial cable. With the recent advent of relatively inexpensive and compact analog-to-digital converters, considerable flexibility is possible in selecting the appropriate place in the system to perform the conversion. However, the limited number of output lines available on a microcomputer processor board usually requires that digital-to-analog conversion be done in the computer on circuit boards designed for the purpose. The outputs from the digital-to-analog converters are amplified and transmitted as analog signals to the actuator drivers.


(Standard Handbook of Machine Design, Robots and Smart Machines, Kenneth J. Waldron, Ph.D.,p47.25)




(new answer)

After the digital signal processor has altered the sound in some desired manner, the hearing aid must present the modified and amplified sound to the aid wearer. As there is no use presenting the aid wearer with a string of numbers, the modified numbers must be converted into an acouistical signal. This conversion is the job of the digital-to-analog converter (DAC) combined with the hearing aid receiver. Digital devices have traditionally done this by having a digital-to-analog converter that outputs an analog voltage, which in turn is fed to a receiver of some type to make the final conversion to sound. To minimize power consumption, digital hearing aids use a different solution. The multiple bits that comprise each sample are converted into a single bit that changes at a rate many times higher than the sample rate. The converter is referred to as a digital-to-digital converter. The high speed serial output from this converter is fed to the receiver, which averages out the high-speed variations in the digitalsignal to produce a smooth analog signal. The receiver thus forms part of the overall digital to analog converter. The electronic part of the digital-to-analog converter can be located either with all the other amplifier parts or inside the metal can that houses the receiver.

(Harvey Dillon, Hearing aids, pg: 36)