Exercise: Digital Electronics

Questions for: Digital Electronics

A current tracer responds to
A:
steady current only
B:
pulsating current only
C:
both pulsating and steady current
D:
none of the above
Answer: B

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

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In which counter does the maximum frequency depend on the modulus?
A:
Synchronous
B:
Ripple
C:
Both synchronous and ripple
D:
Neither synchronous nor ripple
Answer: B

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.

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A dynamic RAM cell which holds 5 V has to be refreshed every 20 ms so that the stored voltage does not fall by more than 0.5 V. If the cell has a constant discharge current of 0.1 pA, the storage capacitance of cell is
A:
4 x 10-6 F
B:
4 x 10-9 F
C:
4 x 10-12 F
D:
4 x 10-15 F
Answer: D

Q = 20 x 10-3 x 0.1 x 10-12 = 2 x 10-15 C and .

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Karnaugh map can not be drawn when the number of variables is more than 4
A:
True
B:
False
C:
D:
Answer: B

K map can be drawn for more than 4 variables.

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ECL has high switching speed because the transistors are
A:
switching between cutoff and saturation regions
B:
switching between cutoff and active regions
C:
switching between active and saturation regions
D:
none of the above
Answer: B

High speed is obtained because saturation state is avoided.

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