Digital to Analog ConverterAdigital-to-analog converter(DAC,D/A,D2AorD-to-A) is a function that converts digital data (usually binary) into ananalog signal(current,voltage, orelectric charge). Digital datacan be transmitted, manipulated, and stored without degradation, albeit with more complex equipment. But a DAC is needed to convert the digital signal to analog to drive an earphone or loudspeaker amplifier in order to produce sound. D/A conversion is the process of converting a value represented in digital code, into a voltage or current which is proportional to the digital value.Analog output=K*Digital input where K is the proportionality factor and is constant value for a given DAC. Output waveform of a DAC fed by a binary counter is as shown. When the binary counter is continuously recycled through its 8 states by applying clock signal, the output will be a staircase waveform of step size 1V. When the counter is at 000, the output of the DAC is minimum (0V). When the counter is at 111, the output of the DAC is maximum (7V).There are various types of DACs1. R-2R ladder Type DAC

2. The Weighted Resistor Type DAC

Important properties of DAC1. Resolution Resolution of a DAC is defined as the smallest change that can occur in an analog output as a result of change in the digital input. Its also defined as the reciprocal of the number of discrete steps in the full scale output of the DAC.% Resolution=% Resolution=

2. Accuracy-Accuracy of a DAC is usually specified in terms of its full scale error and linearity error. The limiting error is the maximum deviation of the analog output from the ideal output.3. Settling time- Operating speed of a DAC is usually specified by giving its settling time. Its defined as the total time between the instant when the digital input changes and the time that the output enters a specified error band for last time.

Analog to Digital ConverterAnanalog-to-digital converter(ADC,A/D, orA to D) is a device that converts a continuous physical quantity (usually voltage) to a digital number that represents the quantity's amplitude. The conversion involvesquantizationof the input, so it necessarily introduces a small amount of error. Instead of doing a single conversion, an ADC often performs the conversions ("samples" the input) periodically. The result is a sequence of digital values that have been converted from a continuous-time and continuous-amplitudeanalog signalto adiscrete-timeand discrete-amplitudedigital signal.

Electric symbolA 3-bit ADC divides the range into 23or eight divisions. A binary or digital code between 000 and 111 represents each division. The ADC translates each measurement of the analog signal to one of the digital divisions. the digital signal does not represent the original signal adequately because the converter has too few digital divisions to represent the varying voltages of the analog signal. The quantization error depends on the number of bits in the converter, along with its errors, noise, and non-linearities.

Types of ADC1. Dual Slope type A/D Converter

2. Successive approximation type ADC