# Digital Electronics - GATE practice papers - Electronics & Communication

1)   What is the crucial function of Emitter-Coupled Logic (ECL) ? (Marks : 01)
- Published on 19 Oct 15

a. Least Power Consumption
b. Saturated Logic Operation
c. Highest Packing Density
d. Maximum Power Consumption
 Answer  Explanation ANSWER: Maximum Power Consumption Explanation: Transistors of ECL always operates in an active or cut-off regions & never goes in saturation region thereby eliminating the storage time. ECL comprises difference amplifiers in addition to emitter followers. These emitter followers are utilized at the output of difference amplifiers for shifting the DC level by consuming maximum power at the requisite level.

2)   It the input clock frequency of eight flip-flops is 768kHz, then what would be the value of its output frequency? (Marks : 01)
- Published on 19 Oct 15

a. 2 kHz
b. 3 kHz
c. 6 kHz
d. 18 kHz
 Answer  Explanation ANSWER: 3 kHz Explanation: Given: Input frequency = 768 kHzThe output frequency of eight flipflops = (1 / 28) x Input frequency = (1 / 28 ) x 768 = 768 / 256 = 3 kHz

3)   Which is the correct truth-table for J-K flip-flop? (Marks : 01)
- Published on 19 Oct 15

a.
b.
c.
d.
 Answer  Explanation ANSWER: Explanation: J-K Flipflop has an ability to overcome the drawbacks of S-R flipflops .When both the inputs of JK flipflop are zero, the output is Qn while when both the inputs are 1, the output is the complement of Qn i.e (Qn). When the inputs are in the form of '0' , '1' & '1','0' respectively, then the outputs are generated in accordance to the J input value; i.e, outputs are '0' & '1' respectively for both the conditions.

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