3. Logic Gates and Circuits

Question 1

Gate

Answer 1

One or a series of devices that perform a basic electrical operation

Question 2

Circuit

Answer 2

Combination of gates, created to perform more complex tasks

Question 3

How do we describe logic gates?

Answer 3

Boolean expressions

Truth Tables

Logic diagrams

Question 4

Boolean expressions

Answer 4

Uses boolean algebra, a mathematical notation to express two valued logic

Question 5

Truth table

Answer 5

Table showing all possible input values and the associated output values

Question 6

Logic diagrams

Answer 6

A graphical representation of a circuit, each gate has its own symbol

Question 7

Transistors

Answer 7

Electrical device with two possible roles:

1) Conductor –> wire that conducts electricity

2) Resistor –> blocks the flow of electricity

–> role depends on the voltage level of an input signal

Acts like a switch

Made of a material that makes it neither a particularly good conductor, nor a particularly good resistor

Question 8

Components of a gate (terminals)

Answer 8

Source

Base

Emitter

–> connected to a ground wire

Question 9

Role of base

Answer 9

Regulates a gate that determines whether the connection between the source and ground is made

Question 10

Transistor functions

Answer 10

1) If base grounds source signal
–> Source is pulled down to 0 volts
–> Base signal is high (transistor on)
== Low output signal –> binary 0

2) If base signal is NOT grounded
–> source signal stays high == 5v
–> Base signal is low (transistor off)
== High output signal –> binary 1

Question 11

Combinatorial Circuits

Answer 11

Input values explicitly determine the output

Question 12

Sequential Circuits

Answer 12

Output is a function of the input values and the existing state of the circuit

Always involve the storage of information