Digital Electronics - Logic Families and Their Characteristics

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"Forgiveness is a virtue of the brave."

- Indira Gandhi

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.

Which of the following logic families has the shortest propagation delay?

A.	CMOS	B.	BiCMOS
C.	ECL	D.	74SXX

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

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.

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 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 V_CC through a 1 k resistor; unused OR and NOR inputs should be grounded.

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