Electronics 4a - Combinational logic

Question 1

What are the voltage values for TTL (transistor-transistor logic) circuits for 0 and 1 values?

Answer 1

• Any volt >2V = ‘1’
• Any volt < 0.8V = ‘0’

Question 2

What are names for two discrete voltages at which digital circuits respond to?

Answer 2

Either:
* High and low
* True and False
* 1 and 0

Question 3

Define combinational logic.

Answer 3

Combinational logic is used when the output of a circtuit is to be a function of the current input state only.

Essentially it will work out the function for this current point in time, ignores past states (unlike sequential logic).

Question 4

What is the truth table for a 3 input AND gate, and its symbol?

Answer 4

Question 5

What is the truth table for a 3 input OR gate, and its symbol?

Answer 5

Question 6

What is the truth table for a 3 input XOR gate, and its symbol?

Answer 6

Question 7

What is the truth table for a 3 input NAND gate, and its symbol?

Answer 7

Question 8

What is the truth table for a 3 input NOR gate, and its symbol?

Answer 8

Question 9

What is the truth table for a 3 input XNOR gate, and its symbol?

Answer 9

Question 10

What is the truth table for an input NOT gate, and its symbol?

Answer 10

Question 11

Solve this question:

Answer 11

Explaination:
* A is 1 when temp rises above a level
* B is 1 when pressure rises above a level
* C is 1 when there is raw materials above a minimum, so we need NOT c for this question.

Question 12

Solve this question:

Answer 12