Page 383 - Op Amps Design, Applications, and Troubleshooting
P. 383

Review Questions  359


                     TABLE 8.4

                     Analog Input                  D/A Output    Comparator Output
                       (Volts)       SAR Status      (Volts)         (Volts)
                         5.7           1000          5.0              Low
                         5.7           1100          7.5             High
                        5.7            1010          6.25            High
                        5.7            1001          5.625            Low




                D/A converter, can be implemented with software internal to a microprocessor.
                However, the speed is generally much slower than a dedicated converter.





        REVIEW QUESTIONS

                1. A certain A/D converter has a 12-bit resolution specification for the analog input
                   range of 0 to 10 volts. What is the smallest voltage change that can be represented in
                   the output?
                2. If the binary output of an A/D converter does not numerically increase with every
                   increase in input voltage, we say the converter is  .
                3. The total time required for an A/D converter to obtain a valid digital output for a
                   given analog input is called  .
                4. Contrast and explain the terms acquisition time and aperture time with reference to
                   sample-and-hold circuits.
                5. Would a weighted D/A converter be the best choice for a 64-bit converter circuit?
                   Explain your answer.
                6. What type of A/D conversion circuit provides the fastest conversion times? What are
                   its disadvantages?
                7. If a certain successive approximation A/D converter requires 10 microseconds to
                   resolve a 0-volt to 2-volt step change on the input, how long will it take to resolve a
                   0-volt to 5-volt step change?
                8. Repeat question 7 for a tracking A/D converter.
                9. The use of a sample-and-hold circuit greatly reduces the highest usable frequency for
                   an A/D converter. (True or False)
                10. Discuss the relationship between droop rate in a sample-and-hold circuit and the
                   necessary conversion time of a subsequent A/D converter circuit.
   378   379   380   381   382   383   384   385   386   387   388