Logic Gates MCQs

1. When the input to an inverter is LOW (0), the output is

(a) HIGH or 0

(b) LOW or 0

(c) HIGH or 1

(d) LOW or 1

2. An inverter performs an operation known as

(a) complementation

(b) assertion

(c) inversion

(d) both answers (a) and (c)

3. The output of an AND gate with inputs A, B and C is 0 (LOW) when

(a) A = 0, B = 0, C = 0

(b) A = 0, B = 1, C = 1

(c) both answers (a) and (b)

4. The output of an OR gate with inputs A, B and C is 0 (LOW) when

(a) A = 0, B = 0, C = 0

(b) A = 0, B = 1, C = 1

(c) both answers (a) and (b)

5. A pulse is applied to each input of a 2-input NAND gate. One pulse goes HIGH at t = 0 and goes back LOW at t = 1 ms. The other pulse goes HIGH at t = 0.8 ms and goes back LOW at t = 3 ms. The output pulse can be described as follows:

(a) It goes LOW at t = 0 and back HIGH at t = 3 ms.
(b) It goes LOW at t = 0.8 ms and back HIGH at t = 3 ms.
(c) It goes LOW at t = 0.8 ms and back HIGH at t = 1 ms.
(d) It goes LOW at t = 0.8 ms and back LOW at t = 1 ms.

6. A pulse is applied to each input of a 2-input NOR gate. One pulse goes HIGH at t = 0 and goes back LOW at t = 1 ms. The other pulse goes HIGH at t = 0.8 ms and goes back LOW at t = 3 ms. The output pulse can be described as follows:

(a) It goes LOW at t = 0 and back HIGH at t = 3 ms.
(b) It goes LOW at t = 0.8 ms and back HIGH at t = 3 ms.
(c) It goes LOW at t = 0.8 ms and back HIGH at t = 1 ms.
(d) It goes HIGH at t = 0.8 ms and back LOW at t = 1 ms.

7. A pulse is applied to each input of an exclusive-OR gate. One pulse goes HIGH at t = 0 and goes back LOW at t = 1 ms. The other pulse goes HIGH at t = 0.8 ms and goes back LOW at t = 3 ms. The output pulse can be described as follows:

(a) It goes HIGH at t = 0 and back LOW at t = 3 ms.
(b) It goes HIGH at t = 0 and back LOW at t = 0.8 ms.
(c) It goes HIGH at t = 1 ms and back LOW at t = 3 ms.
(d) both answers (b) and (c)

8. A positive-going pulse is applied to an inverter. The time interval from the leading edge of the input to the leading edge of the output is 7 ns. This parameter is

(a) speed-power product

(b) propagation delay, tPHL

(c) propagation delay, tPLH

(d) pulse width

9. Most PLDs utilize an array of

(a) NOT gates
(b) NOR gates
(c) OR gates
(d) AND gates