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Digital Electronics - Engineering

Q1:

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

ANS:D - 4 x 10-15 F

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