adc and dac in digital electronics pdf

Adc And Dac In Digital Electronics Pdf

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This ADC architecture runs at moderate speeds and is economical to implement, but relies on the DAC and a good amplifier offset for accuracy. Figure ivmarkt.

Adc And Dac In Digital Electronics Pdf

ESE Undergraduate Labs. Analog-to-Digital ADC. This is a 2 week lab. In first week, you are expected to finish building ADC as shown in Figure 7. You will compare the input signal to the reconstructed output signal. An ADC takes an analog signal and converts it into a binary one, while a DAC converts a binary signal into an analog value.

Figure 1 gives a block diagram of such a system. An example of such a system is a PC sound card. Sensor signals vary continuously "analog" between a specified voltage range. As an example, the output of a microphone gives a voltage between 0 no speech to mV for loud speech.

Any value between these two extremes are possible. The "analog" signal needs to be converted into a "digital" word of n-bits in order to be read into and processed by a computer or digital signal processor - DSP. The "analog" and "digital" signals are shown in Figure 1.

The more bits the output word has the better the resolution. The input-output relationship of an ADC is shown in Figure 2b for a 3-bit converter. Notice that when the analog input signal on the horizontal axis reaches a certain level, a new digital code will be generated see vertical axis in Figure 2b which represents the digital output of the ADC as a function of the analog input. However, if one increases the magnitude of the input signal above 4.

The n-bit word or digital code is a digital representation of a signal. The relationship between the analog output value and the binary word is for the case of a 3-bit code b 2 ,b 1 ,b o , as follows:. The output voltage will then be:.

Notice that only discrete values of the output signal are possible. The more bits the input word has, the smaller the steps of the output signal will be or the better the resolution. Typical ADCs have at least 8 bits of resolution and even 12 to 16 bits are not uncommon. For more bits, one can extend the same principle by using more components. The scheme used in the lab to build these convereters is only one of many possible designs.

For higher resolution converters more sophisticated architectures are used. You will learn more about this in other classes. Pre-lab assignment:. Assume that the voltages in the circuit of Fig. Design an OpAmp interface circuit whose input connects to the output of the R-2R ladder network so that each increment in the binary number produces 1V or a -1V increase decrease in output voltage V DAC e.

Give the circuit and the calculations to find the resistor values. In your lab notebook, calculate the expected analog output voltage at the output of the OpAmp circuit for each of the binary words of Table I. VDAC calc. Vout meas. Draw a diagram similar to the one of Figure 3b in your lab notebook, using the calculated values for V DAC. This circuit takes an analog signal and gives a digital ouput. Figure 5: Flash Analog-to-Digital Converter.

The circuit consists of 4 comparators whose inverting inputs are connected to a voltage divider. A comparator is basically an operational amplifer used without feedback. The outputs of the comparators in Figure 5 correspond to a digital word. When the input rises above V N1 , the first comparator will switch to a high output voltage causing the LED to light up, indicating a For larger input voltages the output of other comparators will switch high as well. For large input voltages above V n3 all comparators will be high corresponding to digital output.

Thus the comparators encode the analog input as a digital word on a thermometer scale. All comparators work in parallel which makes this ADC very fast.

For that reason it is called a Flash Converter. Notice that a 1 kOhm resistor has been added between the power supply and the output of the comparators. This has been done to ensure that the output voltage of the comparators is high enough the comparators have an open collector - don't worry what that means at this point. Calculate and record in your notebook the values of V ni when each comparator will switch. In-lab assignment:. Created by Jan Van der Spiegel, Feb.

Record the values of the input voltage when each LED switches on. To do this, connect the U power suppy instead of the input signal and vary the input slowly to 4V. Note down the value of the voltage when each of the LED lights up.

Digital to Analog Converters

When talking about signals, they can be broadly classified into analog signals and digital signals. In a typical electronics design, these two signals often have to be converted from one form to another. There are many techniques in which this is done, each with its own advantage and disadvantage. In this article we will learn how a DAC works and how it can be used in out designs. A computer is a binary machine operating in an analog world, so to be able to produce an output that is understandable by other devices a DAC is used. For example, a computer stores audio in the form of binary values of the sound wave.

In communication system digital transmission is faster and convenient but the digital signals have to be converted back to analog signals at the receiving terminal. There are several ways of making a digital to analog converter. Some of them are given as under. Ehab A. Almost no current goes into the inverting opamp input because of its -. Introduction to Digital to analog converter.

Analog-to-digital converter

ESE Undergraduate Labs. Analog-to-Digital ADC. This is a 2 week lab. In first week, you are expected to finish building ADC as shown in Figure 7. You will compare the input signal to the reconstructed output signal.

An ADC may also provide an isolated measurement such as an electronic device that converts an input analog voltage or current to a digital number representing the magnitude of the voltage or current. Typically the digital output is a two's complement binary number that is proportional to the input, but there are other possibilities. There are several ADC architectures.

An analog-to-digital converter ADC performs the reverse function. There are several DAC architectures ; the suitability of a DAC for a particular application is determined by figures of merit including: resolution , maximum sampling frequency and others. Digital-to-analog conversion can degrade a signal, so a DAC should be specified that has insignificant errors in terms of the application. DACs are commonly used in music players to convert digital data streams into analog audio signals.

Digital-to-analog converter

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4 comments

StГ©phane G.

Most laboratory instruments either produce or accept analog or continuous signals of some form.

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RГ©my L.

Binary-weighted, and R- 2R Ladder type DAC circuits will be displayed and analyzed. Parallel Comparator or Flash,. Dual Slope, and Successive Approximation.

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