Introducing Digital to Analog Converters (DACs), DACs Functions, Circuits and How DACs Work

By | August 13, 2021

Definition of Digital to Analog Converters (DACs)

Digital to Analog Converters (DACs) is a device for converting a digital input which is generally in binary form into an analog input/signal which is generally in the form of current, voltage or electric charge. In addition, DACs are a link between digital circuits and analog circuits.

Digital to Analog Converters (DACs) are electronic devices that function to convert digital (discrete) signals into analog (continuous) signals. The application of these DACs is as an interface between devices that work with digital systems and analog signal processing devices. These DACs can be electronic circuits and IC DAC chips.

Digital to Analog Converters (DACs) Function

DACs are often used in digital devices on the output side to create an analog signal after the signal has been processed in digital form. The main function of DACs is to convert digital signals into analog signals. DAC circuits are simpler than ADC circuits.

Digital to Analog Converters (DACs) Circuit

There are two basic types of DACs: Binary-weighted DACs and R/2R Ladder DACs. The two types of DACs can be described as follows:

  1. Binary-weighted DACs

A Binary-weighted DACs circuit can be composed of several Resistors and Operational Amplifiers set as amplifiers. In principle, the above DACs circuit can be explained as follows:

The 20 kΩ resistor adds up the current generated by closing switches D0 to D3. Furthermore, these resistors will be scaled in such a way that they suffice the binary-weighted value of the current which will then be added up by the 20 kΩ resistor. Closing switch D0 causes a current of 50 A to flow through the 20 kΩ resistor, producing a voltage of -1 V at Vout.

The closing of each switch results in a doubling of the current value generated from the previous switch. The conversion values ​​for the switch closing combinations are shown in the following table.

Conversion from digital to analog value based on the Binary Weighted DACs circuit above.

  1. R/2R Ladder DACs

Besides the Binary Weighted DACs, there is another method of converting Digital to Analog, namely the R/2R Ladder. This method is widely used in DACs ICs. In the R/2R Ladder circuit, only two resistor values ​​are required, which can be used for DACs ICs with 8, 10 or 12 bit resolution.

The working principle of the R / 2R Ladder circuit is as follows:

4-bit digital information enters from switch D0 to switch D3. This switch has a state of “1” (approximately 5 V) or “0” (approximately 0 V). By setting the switch will result in a change in the voltage given to the inverting summing amplifier according to its binary equivalent value. For example, if D0 = 0, D1 = 0, D2 = 0 and D3 = 1, then R1 will be parallel to R5 giving 10 k .

Then this 10 k is in series with R6 = 10 k to produce 20 k. This 20 k parallels R2 to produce 10 k , and so on until R7, R3 and R8. So that the equivalent circuit is obtained as shown below.

So that the analog output voltage (Vout) of the R/2R Ladder DACs circuit above can be calculated using the equation:

The Vout obtained from this switch combination is -5V. The combination values ​​and conversion results of the R/2R Ladder DAC circuit will be shown in the following table.

How Digital to Analog Converters (DACs) Works

The main function of the DACs is to convert digital signals into analog signals. The DAC circuit is simpler than the ADC circuit.

If we play music via DAP (Digital Audio Player), it must already have a DACs in it. The internal DACs of the DAP can be bypassed to the external DACs, so that sound processing is carried out on the external DACs, so that the quality is better. Likewise, if we use a PC / laptop to play music, and our PC / laptop soundcard is not good, we can use an external DACs connected via USB, so we get better sound quality.

Types of Digital to Analog Converters (DACs)

Based on the energy source, the DACs on the market is divided into three, desktop DACs, USB DACs, and portable.

  1. Desktop DACs is powered by household electricity, then uses an adapter. Can not live without electricity at home.
  2. The USB DACs is powered by a USB slot which also functions as a data line.
  3. Portable DACs is powered by a battery that is embedded in it, so it can be turned on without electricity at home or a PC / laptop.