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

  • Which of the statements below best describes the basic operation of a dual-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. Two ramps are generated: one by the input voltage and the other by a reference voltage. The input voltage ramp charges the integrating capacitor, while the reference voltage discharges the capacitor and enables the counter until the capacitor is discharged, at which time the counter value is loaded into the output latches.

  • Correct Answer
  • Two ramps are generated: one by the input voltage and the other by a reference voltage. The input voltage ramp charges the integrating capacitor, while the reference voltage discharges the capacitor and enables the counter until the capacitor is discharged, at which time the counter value is loaded into the output latches. 

    • More questions

    • 1. The content of a simple programmable logic device (PLD) consists of:

    • Options
    • A. fuse-link arrays
    • B. thousands of basic logic gates
    • C. advanced sequential logic functions
    • D. thousands of basic logic gates and advanced sequential logic functions
      • Discuss
    • 2. A counter has a specified sequence of states, but a shift register does not.

    • Options
    • A. True
    • B. False
      • Discuss
    • 3. ROMs are used to store data on a permanent basis.

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. A microprocessor with the necessary support circuits will include at least two memory ICs: ROM or EPROM, and a RAM.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. What is the acquisition time of the AD1154 sample-and-hold IC?

    • Options
    • A. 1.5 µs
    • B. 2.5 µs
    • C. 3.5 µs
    • D. 4.5 µs
      • Discuss
    • 6. Which of the figures shown below represents the exclusive-NOR gate?


    • Options
    • A. a
    • B. b
    • C. c
    • D. d
      • Discuss
    • 7. The device that places its input data onto one of several outputs is a ________.

    • Options
    • A. demultiplexer
    • B. multiplexer
    • C. comparator
    • D. counter
      • Discuss
    • 8. Digital computers use an easier method to subtract binary numbers, called one's complement.

    • Options
    • A. True
    • B. False
      • Discuss
    • 9. With interrupt-driven I/O, if two or more devices request service at the same time, ________.

    • Options
    • A. the device closest to the CPU gets priority
    • B. the device that is fastest gets priority
    • C. the device assigned the highest priority is serviced first
    • D. the system is likely to crash
      • Discuss
    • 10. Asynchronous counters are often called ________ counters.

    • Options
    • A. toggle
    • B. ripple
    • C. binary
    • D. flip-flop
      • Discuss

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