In electronics, the DAC circuit is a kind of system. It is she who converts the digital signal to analog.
There are several DAC circuits. Suitability for a particular application is determined by quality metrics including resolution, maximum sample rate, and others.
Digital-to-analogue conversion can degrade the sending of the signal, so it is necessary to find an instrument that has minor errors in terms of application.
Applications
DACs are typically used in music players to convert numerical streams of information into analog audio signals. They are also used in televisions and mobile phones to convert video data into video signals, respectively, which are connected to screen drivers to display monochromatic or multi-colored images.
It is these two applications that use DAC circuits at opposite ends of the compromise between density and pixel count. Audio is a low frequency type with high resolution and video is a high frequency variant with a low to medium image.
Due to complexity and the need for carefully matched components, all but the most specialized DACs are implemented as integrated circuits (ICs). Discrete links are typically extremely fast, low-resolution, power-saving types that are used in military radar systems. Very high speed test equipment, especially sampling oscilloscopes, can also use discrete DACs.
Overview
The semi-constant output of a conventional unfiltered DAC is built into almost any device, and the initial image or final bandwidth of the design smoothes the pitch response into a continuous curve.
Answering the question: “What is a DAC?”, it is worth noting that this component converts an abstract number of finite precision (usually a binary fixed-point digit) into a physical value (for example, voltage or pressure). In particular, D/A conversion is often used to change time series data into a continuously changing physical signal.
The ideal DAC converts abstract digits into a conceptual train of pulses, which are then processed by a reconstruction filter, using some form of interpolation to fill in the data between pulses. Ordinarya practical digital-to-analogue converter changes the numbers into a piecewise constant function made up of a sequence of rectangular patterns that are created holding the zeroth order. Also, answering the question, "What is a DAC?" it is worth noting other methods (for example, based on delta-sigma modulation). They create a pulse-density modulated output that can be similarly filtered to produce a smoothly varying signal.
According to the Nyquist-Shannon sampling theorem, the DAC can reconstruct the original vibration from the sampled data, provided that its penetration zone meets certain requirements (for example, a baseband pulse with a lower line density). The digital sample represents the quantization error, which appears as low-level noise in the reconstructed signal.
Simplified function diagram of an 8-bit tool
It's worth noting right away that the most popular model is the Real Cable NANO-DAC digital-to-analogue converter. The DAC is part of an advanced technology that has made a significant contribution to the digital revolution. To illustrate, consider typical long distance phone calls.
The caller's voice is converted into an analog electrical signal using a microphone, and then this pulse is changed into a digital stream along with the DAC. After that, the latter is divided into network packets, where it can be sent along with other digital data. And it may not necessarily be audio.
Then packagesare accepted at the destination, but each of them may take a completely different route and not even reach the destination in the correct order and at the correct time. The digital voice data is then extracted from the packets and assembled into a common data stream. The DAC converts this back into an analog electrical signal that drives an audio amplifier (such as the Real Cable NANO-DAC digital-to-analog converter). And he, in turn, activates the loudspeaker, which finally produces the necessary sound.
Audio
Most modern acoustic signals are stored digitally (eg MP3 and CD). In order to be heard through the speakers, they must be converted into a similar impulse. So you can find a digital-to-analog converter for TV, CD player, digital music systems and PC sound cards.
Dedicated standalone DACs can also be found in high quality Hi-Fi systems. They typically take the digital output of a compatible CD player or dedicated vehicle and convert the signal to a line-level analog output that can then be fed into an amplifier to drive speakers.
Similar D/A converters can be found in digital columns such as USB speakers and sound cards.
In Voice over IP applications, the source must first be digitized for transmission, so it is converted via an ADC and then converted to analog using a DAC onthe receiving party. For example, this method is used for some digital-to-analog converters (TV).
Picture
Sampling tends to operate on a completely different scale overall, due to the highly non-linear response of both cathode ray tubes (which the vast majority of digital video production has been destined for) and the human eye, using a gamma curve to provide the appearance of evenly distributed brightness steps over the entire dynamic range of the display. Hence the need to use RAMDAC in computer video applications with a fairly deep color resolution, so that it is impractical to create a hard-coded value in the DAC for each output level of each channel (for example, an Atari ST or Sega Genesis would need 24 of these values; a 24-bit video card would need 768).
Because of this inherent distortion, it is not uncommon for a television or video projector to be truthfully stated to have a linear contrast ratio (the difference between the darkest and brightest output levels) of 1,000:1 or more. This is equivalent to 10 bits of sound fidelity, even if it can only receive signals with 8-bit fidelity and use an LCD panel that only displays six or seven bits per channel. DAC reviews are published on this basis.
Video signals from a digital source such as a computer must be converted to analog form if they are to be displayed on a monitor. Similar since 2007inputs were used more frequently than digital, but this has changed as flat panel displays with DVI or HDMI connections have become more common. However, a video DAC is built into any digital video player with the same outputs. A digital-to-analog audio converter is usually integrated with some kind of memory (RAM) that contains reorganization tables for gamma correction, contrast, and brightness to create a fixture called RAMDAC.
The device that is remotely connected to the DAC is a digitally controlled potentiometer used to pick up the signal.
Mechanical design
For example, the IBM Selectric typewriter already uses a non-manual DAC to drive the ball.
Digital-to-analogue converter circuit looks like this.
Single-bit mechanical drive takes two positions: one when turned on, the other when turned off. The movement of multiple single bit actuators can be combined and weighted by the device without hesitation to obtain more accurate steps.
It is the IBM Selectric typewriter that uses such a system.
Main types of digital-to-analog converters
- Pulse width modulator where a stable current or voltage is switched into a low-pass analog filter with a duration determined by a digital input code. This method is often used to control motor speed and dim LED lights.
- Digital to analog audio converter withoversampling or interpolating DACs, such as those using delta-sigma modulation, use the pulse density variation method. Speeds over 100 ksample per second (e.g. 180 kHz) and 28-bit resolution are achievable with a delta-sigma device.
- A binary weighted element that contains separate electrical components for each DAC bit connected to the summation point. It is she who can add up the operational amplifier. The current strength of the source is proportional to the weight of the bit to which it corresponds. Thus, all non-zero bits of the code are added to the weight. This is because they have the same voltage source at their disposal. This is one of the fastest conversion methods, but it's not perfect. Since there is a problem: low fidelity due to the large data required for each individual voltage or current. Such high-precision components are expensive, so this type of model is usually limited to 8-bit resolution or even less. The switched resistor has the purpose of digital-to-analog converters in parallel network sources. Individual instances are connected to electricity based on a digital input. The principle of operation of this type of digital-to-analog converter lies in the switched current source of the DAC, from which different keys are selected based on a numerical input. It includes a synchronous capacitor line. These single elements are connected or disconnected using a special mechanism (foot) that is located near all plugs.
- Digital-to-analogue stairway converterstype, which is a binary-weighted element. It, in turn, uses a repeating structure of the cascaded resistor values R and 2R. This improves accuracy due to the relative ease of fabrication of the same rated mechanism (or current sources).
- Sequential advance or cyclic DAC that builds the output one by one during each step. Individual bits of a digital input are processed by all connectors until the entire object is accounted for.
- Thermometer is a coded DAC that contains an equal resistor or current-source segment for each possible value of the DAC output. An 8-bit thermometer DAC will have 255 elements, and a 16-bit thermometer DAC will have 65,535 parts. This is perhaps the fastest and most accurate DAC architecture, but at the expense of high cost. With this type of DAC, conversion rates of over one billion samples per second have been achieved.
- Hybrid DACs that use a combination of the above methods in a single converter. Most DAC ICs are of this type due to the difficulty of getting low cost, high speed, and accuracy all in one device.
- Segmented DAC that combines the principle of thermometer coding for higher digits and binary weighting for lower components. In this way, a compromise is reached between accuracy (using the thermometer coding principle) and the number of resistors or current sources (using binary weighting). Deep device with doubleaction means segmentation is 0%, and design with full thermometric coding has 100%.
Most of the DACS on this list rely on a constant voltage reference to create their output value. Alternatively, the multiplying DAC accepts AC input voltage to convert them. This imposes additional design constraints on the bandwidth of the reorganization scheme. Now it’s clear why digital-to-analog converters of various types are needed.
Performance
DACs are very important for system performance. The most significant characteristics of these devices is the resolution that is created for the use of a digital-to-analog converter.
The number of possible output levels a DAC is designed to play is usually stated as the number of bits it uses, which is the base two logarithm of the number of levels. For example, a 1-bit DAC is designed to play two circuits, while an 8-bit DAC is designed to play 256 circuits. The padding is related to the effective number of bits, which is a measure of the actual resolution achieved by the DAC. Resolution determines the color depth in video applications and the audio bit rate in audio devices.
Max frequency
Measuring the fastest speed a DAC circuit can operate at and still produce the correct output determines the relationship between it and the bandwidth of the sampled signal. As stated above, the theoremNyquist-Shannon samples relates continuous and discrete signals and claims that any signal can be reconstructed with any accuracy from its discrete records.
Monotonicity
This concept refers to the ability of the DAC's analog output to move only in the direction that the digital input moves. This characteristic is very important for DACs used as a low frequency signal source.
Total harmonic distortion and noise (THD + N)
Measurement of distortion and extraneous sounds introduced by the DAC into the signal, expressed as a percentage of the total amount of unwanted harmonic distortion and noise that accompanies the desired signal. This is a very important feature for dynamic and low output DAC applications.
Range
A measure of the difference between the largest and smallest signals a DAC can reproduce, expressed in decibels, is usually related to resolution and noise level.
Other measurements such as phase distortion and jitter can also be very important for some applications. There are those (eg, wireless data transmission, composite video) that can even rely on accurately receiving phase-adjusted signals.
Linear PCM audio sampling typically works on a resolution of each bit equivalent to six decibels of amplitude (doubling the volume or accuracy).
Nonlinear PCM encodings (A-law / Μ-law, ADPCM, NICAM) try to improve their effective dynamic ranges in various ways -logarithmic step sizes between the output audio levels represented by each bit of data.
Classification of digital-to-analog converters
Classification by non-linearity divides them into:
- Distinctive non-linearity, which shows how two neighboring code values deviate from the perfect 1 LSB step.
- Cumulative non-linearity indicates how far the DAC's transmission deviates from ideal.
So the ideal feature is usually a straight line. INL shows how much the actual voltage at a given code value differs from this line in the least significant bits.
Boost
Ultimately noise is limited by thermal hum generated by passive components such as resistors. For audio applications and at room temperature, this is typically just under 1 µV (microvolt) of white signal. This limits performance to less than 20 bits even in 24-bit DACs.
Performance in the frequency domain
Spurious-free dynamic range (SFDR) indicates in dB the ratio of the powers of the converted main signal to the largest unwanted overshoot.
Noise Distortion Ratio (SNDR) indicates in dB the power property of the converted main sound to its sum.
Total harmonic distortion (THD) is the sum of the powers of all HDi.
If the maximum DNL error is less than 1 LSB, then the digital-to-analog converter is guaranteedwill be uniform. However, many monotonic instruments can have a maximum DNL greater than 1 LSB.
Time domain performance:
- Glitch impulse zone (glitch energy).
- Uncertainty of the answer.
- Nonlinearity time (TNL).
DAC Basic Operations
An analog-to-digital converter takes an exact number (most often a fixed-point binary number) and converts it into a physical quantity (such as voltage or pressure). DACs are often used to reorganize finite precision time series data into a continuously changing physical signal.
The ideal D/A converter takes abstract numbers from a train of pulses, which are then processed using a form of interpolation to fill in data between signals. A conventional digital-to-analogue converter puts the numbers into a piecewise constant function consisting of a sequence of rectangular values, which is modeled with zero-order hold.
The converter restores the original signals so that its bandwidth meets certain requirements. Digital sampling is accompanied by quantization errors that create low level noise. It is he who is added to the restored signal. The minimum amplitude of an analog sound that can cause a digital sound to change is called the least significant bit (LSB). And the error (rounding) that occurs between the analog and digital signals,is called quantization error.
