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Home ‣ Digital Electronics ‣ Interfacing to the Analog World See What Others Are Saying!
  • Question

  • Which of the following describes the basic operation of a single-slope A/D converter.


  • Options
  • A. The input voltage is used to set the frequency of a voltage-controlled oscillator (VCO). The VCO quits changing frequency when the input voltage stabilizes. The frequency of the VCO, which is proportional to the analog input voltage, is measured and is displayed on the digital display as a voltage reading.
  • B. A ramp generator is used to enable a counter through a comparator. When the ramp voltage equals the input voltage the counter is latched and then reset. The counter reading is proportional to the input voltage since the ramp is changing at a constant V/second rate.
  • C. A ramp voltage and analog input voltage are applied to a comparator. As the input voltage causes the integrating capacitor to charge, it will at some point equal the ramp voltage. The ramp voltage is measured and displayed on the digital panel meter.
  • D. Any of the above could be correct, depending on the specific type of A/D converter involved.

  • Correct Answer
  • A ramp generator is used to enable a counter through a comparator. When the ramp voltage equals the input voltage the counter is latched and then reset. The counter reading is proportional to the input voltage since the ramp is changing at a constant V/second rate. 

    • More questions

    • 1. Why is a pull-up resistor needed when connecting TTL logic to CMOS logic?

    • Options
    • A. to increase the output LOW voltage
    • B. to decrease the output LOW voltage
    • C. to increase the output HIGH voltage
    • D. to decrease the output HIGH voltage
      • Discuss
    • 2. The total sink current decreases with an increase in each load gate input.

    • Options
    • A. True
    • B. False
      • Discuss
    • 3. The wave-drive sequence of a stepper motor has more torque and operates more smoothly than the full-step sequence at moderate speeds.

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. In order to select data input I1 of a 74151 eight-line multiplexer, the select inputs must be:

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. An RC circuit used in a 74122 retriggerable one-shot has an REXT of 100 kΩ and a CEXT of 0.005 µF. The pulse width is ________.

    • Options
    • A. 70 µs
    • B. 16 µs
    • C. 160 µs
    • D. 32 µs
      • Discuss
    • 6. When converting from decimal to binary by the repeated division-by-two method, the initial remainder becomes the MSD.

    • Options
    • A. True
    • B. False
      • Discuss
    • 7. The 74S124 TTL chip is a voltage-controlled oscillator that will generate a specific frequency at Vout.

    • Options
    • A. True
    • B. False
      • Discuss
    • 8. A major application for DSP is in ________ and ________ of analog signals.

    • Options
    • A. sending, receiving
    • B. digitizing, weighting
    • C. filtering, conditioning
    • D. leveling, translating
      • Discuss
    • 9. The speed-power product provides a basis for the comparison of logic circuits when power dissipation and propagation delay are important considerations in the selection of the type of logic to be used.

    • Options
    • A. True
    • B. False
      • Discuss
    • 10. An RC circuit used in a nonretriggerable 74121 one-shot has an REXT of 49 kΩ and a CEXT of 0.2 µF. The pulse width (tW) is approximately ________.

    • Options
    • A. 6.9 µs
    • B. 6.9 ms
    • C. 69 ms
    • D. 690 ms
      • Discuss

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