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# Digital Logic - Combinational Circuits

16:

A one-to-four line demultiplexer is to be implemented using a memory. How many bits must each word have ?

 A. 1 bit B. 2 bits C. 4 bits D. 8 bits Answer Report Discuss Option: A Explanation : 2 select line A and B will work as address lines, so we have 4 addresses (or words) Each word will have 4 bits so memory required is 4 x 4 = 16 bits Click on Discuss to view users comments. alina said: (1:57am on Sunday 28th May 2017) t o represent four lines we have to use two bits. Write your comments here:
17:   What logic function is produced by adding an inverter to the output of an AND gate ?
 A. NAND B. NOR C. XOR D. OR Answer Report Discuss Option: A Explanation : Click on Discuss to view users comments. Write your comments here:
18:   Which of the following gates is known as coincidence detector ?
 A. AND gate B. OR gate C. NOT gate D. NAND gate Answer Report Discuss Option: A Explanation : Click on Discuss to view users comments. Write your comments here:
19:   Which table shows the logical state of a digital circuit output for every possible combination of logical states in the inputs ?
 A. Function table B. Truth table C. Routing table D. ASCII table Answer Report Discuss Option: B Explanation : Click on Discuss to view users comments. Write your comments here:
20:

A positive AND gate is also a negative

 A. NAND gate B. NOR gate C. AND gate D. OR gate Answer Report Discuss Option: D Explanation : Truth Table For AND  ```0 0 => 0 0 1 => 0 1 0 => 0 1 1 => 1``` Now invert all values (as if you place inverters on the two inputs and the one output): ```1 1 => 1 1 0 => 1 0 1 => 1 0 0 => 0``` Click on Discuss to view users comments. Write your comments here: X