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Thursday, October 13, 2011

8-BIT A/D CONVERTER – IC APPLICATIONS LAB FOR JNTU UNIVERSITY STUDENTS




8-BIT A/D CONVERTER


Aim: To find the digital output value for a given analog signal using ADC 0808.

Apparatus:

1.     8-bit A/D converter kit
2.     Connecting wires
3.     Digital Multimeter

Circuit Description:

Analog to Digital converters are used in all computer applications that require interface with the analog world. In addition, if a digital read out of an analog measurement is needed, a stand-alone ADC can be used to generate the bit patterns required to drive a decimal or hexadecimal display. The method of successive approximation is widely used because of its accuracy and speed.
 We can get the theoretical output value using below equation
                    
               (A/D input voltage)/1 LSB value(=Vref/2n)


For Example: 

                      Input voltage= 1.00Volts.
                      1 LSB value = 5/256 =0.01953V.
                      Output voltage      = 1/0.01953
                                                         = 51.2 (10)
                                                         = 33(16)
                                                         = 00110011(2)






 Circuit Diagram:


















Tabular form:



















Procedure:

1.     Study the operation of the circuit.
2.     As the circuitry is already wired , connect trainer to the mains and switch on the power supply.
3.     Measure the output voltages of regulated power supply circuit that is +5 volts.
4.     Set the input at the voltages shown in table1 and fill the reminder of the table.
5.      Show how you arrived at the calculated output values. The calculated output can be found as in figure 1 or you may calculate the nearest 8-bit number to the analog voltage.
6.     Note down output voltages for different combinations of digital inputs and compare it with the theoretical value.


Result:  
            

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