Number of inputs on each gate

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. How many inputs does a NOT gate have?

A One input

B Two inputs

2. How many inputs does an AND gate have in this course?

A Three inputs

B Exactly two inputs

3. Which gate is the odd one out because it has a different number of inputs?

A NOT

B XOR

4. A student draws a NOR gate with three input wires going into it. Is this allowed in this course?

A Yes, NOR can take three inputs

B No, NOR has exactly two inputs

5. A truth table for a single NOT gate with input A needs how many input columns?

A One input column (A)

B Two input columns (A and B)

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1X = NOT A		AA two-input gate: NAND always takes exactly two inputs, A and B
2X = A NAND B		BThis uses an AND gate with three inputs. No gate has three inputs, so two gates must be combined, for example (A AND B) AND C.
3Combining two gates to handle three inputs A, B and C, because no gate has three inputs		CNOT is given two inputs, but it has exactly one input. It should be NOT A, or NOT applied to a single input or bracket.
4Only one gate in this course has a single input		DThe NOT gate has exactly one input (A) and one output (X)
5X = A AND B AND C		EX = NOT B
6X = NOT A B		FX = (A AND B) OR C

Definitions

NOT: 1 input, others: 2

Fill in the Blanks

Complete each line of code by filling in the missing parts.

// one input only X = ___ A

// NOT has _ input

// NAND, NOR and XOR each have _ inputs

// three inputs: A, B and C X = (A AND B) OR _

// two gates, three inputs X = _A OR B) AND C

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A P = NOT A

B Q = A OR B

C R = A NAND B NAND C

D S = A XOR B

Question 2

A # Inputs A, B and C

B T = A AND B

C U = T AND C

D X = NOT(U, C)

Question 3

A # Two inputs: A and B

B P = A AND B

C Q = A OR B

D X = XOR(P, Q, A)

Question 4

A NOT gate: 2 inputs

B AND gate: 2 inputs

C OR gate: 2 inputs

Question 5

A NAND gate: 2 inputs

B NOR gate: 2 inputs

C XOR gate: 3 inputs

D NOT gate: 1 input

Answer Key

Number of inputs on each gate

Section A: Quick Questions

A — One input

B — Exactly two inputs

A — NOT

B — No, NOR has exactly two inputs

A — One input column (A)

Section B: Match the Pairs

X = NOT A → The NOT gate has exactly one input (A) and one output (X)

X = A NAND B → A two-input gate: NAND always takes exactly two inputs, A and B

Combining two gates to handle three inputs A, B and C, because no gate has three inputs → X = (A AND B) OR C

Only one gate in this course has a single input → X = NOT B

X = A AND B AND C → This uses an AND gate with three inputs. No gate has three inputs, so two gates must be combined, for example (A AND B) AND C.

X = NOT A B → NOT is given two inputs, but it has exactly one input. It should be NOT A, or NOT applied to a single input or bracket.

Section C: Definitions

NOT: 1 input, others: 2 — NOT has exactly one input. AND, OR, NAND, NOR and XOR each have exactly two inputs. No three-input gates in this course, so join two gates for three inputs.

Section D: Fill in the Blanks

// one input only
X = NOT A

// NOT has 1 input

// NAND, NOR and XOR each have 2 inputs

// three inputs: A, B and C
X = (A AND B) OR C

// two gates, three inputs
X = (A OR B) AND C

Section E: Spot the Error

C — NAND has exactly two inputs, so it cannot take A, B and C together. It should be R = A NAND B.

D — NOT is a single-input gate, so it cannot take two inputs. It should be X = NOT U.

D — XOR has exactly two inputs, so it cannot take three. It should be X = P XOR Q.

A — NOT is the only gate with a single input. It should read NOT gate: 1 input.

C — There are no three-input gates in this course. XOR has exactly two inputs, so it should read XOR gate: 2 inputs.