Logic Families and Their Characteristcs Questions and Answers

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Q1
What is unique about TTL devices such as the 74SXX?
  • A These devices use Schottky transistors and diodes to prevent them from going into saturation; this results in faster turn-on and turn-off times, which translates into higher frequency operation.
  • B The gate transistors are silicon (S), and the gates therefore have lower values of leakage current.
  • C The S denotes the fact that a single gate is present in the IC rather than the usual package of 2–6 gates.
  • D The S denotes a slow version of the device, which is a consequence of its higher power rating.
Answer: Option A
Q2
Which of the following logic families has the shortest propagation delay?
  • A CMOS
  • B BiCMOS
  • C ECL
  • D 74SXX
Answer: Option C
Q3
Why must CMOS devices be handled with care?
  • A so they don’t get dirty
  • B because they break easily
  • C because they can be damaged by static electricity discharge
Answer: Option C
Q4
Special handling precautions should be taken when working with MOS devices. Which of the following statements is not one of these precautions?
  • A All test equipment should be grounded.
  • B MOS devices should have their leads shorted together for shipment and storage.
  • C Never remove or insert MOS devices with the power on.
  • D Workers handling MOS devices should not have grounding straps attached to their wrists.
Answer: Option D
Q5
What should be done to unused inputs on TTL gates?
  • A They should be left disconnected so as not to produce a load on any of the other circuits and to minimize power loading on the voltage source.
  • B All unused gates should be connected together and tied to V< sub=""> through a 1 k resistor.<>
  • C All unused inputs should be connected to an unused output; this will ensure compatible loading on both the unused inputs and unused outputs.
  • D Unused AND and NAND inputs should be tied to VCC through a 1 k resistor; unused OR and NOR inputs should be grounded.
Answer: Option D
Q6
Assume that a particular IC has a supply voltage (Vcc) equal to +5 V and ICCH = 10 mA and ICCL = 23 mA. What is the power dissipation for the chip?
  • A 50 mW
  • B 82.5 mW
  • C 115 mW
  • D 165 mW
Answer: Option B
Q7
Can a 74HCMOS logic gate directly connect to a 74ALSTTL gate?
  • A Yes
  • B No
Answer: Option A
Q8
What is the major advantage of ECL logic?
  • A very high speed
  • B wide range of operating voltage
  • C very low cost
  • D very high power
Answer: Option A
Q9
As a general rule, the lower the value of the speed–power product, the better the device because of its:
  • A long propagation delay and high power consumption
  • B long propagation delay and low power consumption
Answer: Option B
Q10
What is the range of invalid TTL output voltage?
  • A 0.0–0.4 V
  • B 0.4–2.4 V
  • C 2.4–5.0 V
  • D 0.0–5.0 V
Answer: Option B

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