DAC, Overview

DAC, OverviewDigital-analog converters (or DACs) are mostly used for connecting digital devices and systems with external analog signals.In this case DAC converts digital output signals of devices to analog signals.In general, the DAC chip can be represented as a block with multiple digital inputs and 1 analog input, and an analog output. N-bit N code is fed to digital inputs of the DAC, and Urv reference voltage is fed to the analog input.UO voltage or IO current is the output signal. In this case the output current or output voltage is proportional to the input code and reference voltage.For some chips reference voltage must have a strictly specified level, for others it is permitted to change the value within a wide range, including change of its polarity.The DAC with a large range of reference voltage variation is called the multiplying DAC, since it can easily be used to multiply the input code to any voltage reference.In addition to data signals, DAC chips also require connection of 1 or 2 power supplies and a common wire. Typically DAC digital inputs ensure compatibility with standard TTL output circuits. Most often, if a DAC has a current output, its output current is converted to an output voltage by an external operational amplifier and a built-in ROC resistor with one of the outputs derived to the external chip output.The essence of conversion of the input digital code into the analog output signal is quite simple. It is the summation of several currents (according to the number of bits of the input code) with which each successive one being twice larger than the previous one.Either transistor current sources or resistive matrixes switched by transistor keys are used to obtain these currents.DAC chips differ in the number of digits, the value of postponing a conversion, the permissible value of the reference voltage, the values of conversion errors and other parameters. They differ also in production technology and characteristics of the internal structure, which often imposes restrictions on their use. So choose a DAC chip for a particular application and refer to detailed information provided by manufacturers.