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Electronics and Communication Engineering - Digital Electronics

Exercise : Digital Electronics - Section 3
31.
In which counter does the maximum frequency depend on the modulus?
Synchronous
Ripple
Both synchronous and ripple
Neither synchronous nor ripple
Answer: Option
Explanation:

Since propagation delays of all flip-flops are added in ripple counter, the maximum frequency depends on the number of flip-flops which depends on modulus.

32.
A current tracer responds to
steady current only
pulsating current only
both pulsating and steady current
none of the above
Answer: Option
Explanation:

The indicator of current tracer glows when its tip is held over a pulsating current path.

33.
A presettable counter with 4 flip flops can start counting from
0000
1000
any number from 0000 to 1000
any number from 0000 to 1111
Answer: Option
Explanation:

Since 4 flip-flops are used it can count from 0000 to 1111. By presetting it can start from any number.

34.
A logical expression Y = A + AB is equal to
Y = AB
Y = AB
Y = A + B
Y = A + B
Answer: Option
Explanation:

Y = A + A B = (A + A) (A + B) = (A + B).

35.
Using the same flip flops
a synchronous flip flop can operate at higher frequency than ripple counter
a ripple counter can operate at higher frequency than synchronous counter
both ripple and synchronous counter can operate at the same frequency
can not determine
Answer: Option
Explanation:

In a synchronous counter clock pulses are applied to all flip-flops simultaneously. Hence minimum time delay and high frequency.

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