Unit 7 chapter 24
Download
1 / 47

Unit 7, Chapter 24 - PowerPoint PPT Presentation


  • 147 Views
  • Uploaded on

Unit 7, Chapter 24. CPO Science Foundations of Physics. Unit 7: Electricity and Magnetism. Chapter 24 Electricity and Magnetism. 24.1 Semiconductors 24.2 Circuits with Diodes and Transistors 24.3 Digital Electronics. Chapter 24 Objectives.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Unit 7, Chapter 24' - randi


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Unit 7 chapter 24 l.jpg
Unit 7, Chapter 24

CPO Science

Foundations of Physics


Unit 7 electricity and magnetism l.jpg
Unit 7: Electricity and Magnetism

Chapter 24 Electricity and Magnetism

  • 24.1 Semiconductors

  • 24.2 Circuits with Diodes and Transistors

  • 24.3 Digital Electronics


Chapter 24 objectives l.jpg
Chapter 24 Objectives

  • Describe how a diode and transistor work in terms of current and voltage.

  • Explain the difference between a p-type and an n-type semiconductor.

  • Construct a half-wave rectifier circuit with a diode.

  • Construct a transistor switch.

  • Describe the relationship between inputs and outputs of the four basic logic gates.

  • Construct an adding circuit with logic gates.


Chapter 24 vocabulary terms l.jpg
Chapter 24 Vocabulary Terms

  • forward bias

  • reverse bias

  • bias voltage

  • p-type

  • n-type

  • depletion region

  • hole

  • collector

  • emitter

  • base

  • conductivity

  • p-n junction

  • logic gate

  • rectifier

  • diode

  • transistor

  • amplifier

  • gain

  • analog

  • digital

  • AND

  • OR

  • NAND

  • NOR

  • binary

  • CPU

  • program

  • memory

  • bit

  • integrated circuit


24 1 semiconductors l.jpg

Key Question:

What are some useful properties of semiconductors?

24.1 Semiconductors

*Students read Section 24.1 AFTER Investigation 24.1


24 1 diodes l.jpg
24.1 Diodes

  • A diode is a one-way valve for electric current.

  • Diodes are a basic building block of all electronics and are used to control the direction of current flowing in circuits.


24 1 diodes7 l.jpg
24.1 Diodes

  • When a diode is connected in a circuit so current flows through it, we say the diode is forward biased.

  • When the diode is reversed so it blocks the flow of current, the diode is reverse biased.


24 1 diodes8 l.jpg

In a forward-biased diode the current stays at zero until the voltage reaches the bias voltage (Vb), which is 0.6 V for common silicon diodes.

You can think of the bias voltage as the amount of energy difference it takes to open the diode.

24.1 Diodes


24 1 transistors l.jpg
24.1 Transistors the voltage reaches the

  • A transistor allows you to controlthe current, not just block it in one direction.

  • A good analogy for a transistor is a pipe with an adjustable gate.


24 1 transistors10 l.jpg

A transistor has the voltage reaches the three terminals.

The main path for current is between the collector and emitter.

The base controls how much current flows, just like the gate controlled the flow of water in the pipe.

24.1 Transistors


24 1 transistors11 l.jpg

The current versus voltage graph for a transistor is more complicated than for a simple resistor because there are three variables.

A transistor is very sensitive; ten-millionths of an amp makes a big difference in the resistance between the collector and emitter.

24.1 Transistors


24 1 conductivity and semiconductors l.jpg
24.1 Conductivity and semiconductors complicated than for a simple resistor because there are three variables.

  • The relative ease at which electric current flows through a material is known as conductivity.

  • Conductors (like copper) have very high conductivity.

  • Insulators (like rubber) have very low conductivity.

  • The conductivity of a semiconductor depends on its conditions.

  • For example, at low temperatures and low voltages a semiconductor acts like an insulator.

  • When the temperature and/or the voltage is increased, the conductivity increases and the material acts more like a conductor.


24 1 metals as conductors l.jpg
24.1 Metals as conductors complicated than for a simple resistor because there are three variables.

  • Metals are good conductors because a small percentage of electrons are free to separate from atoms and move independently.


24 1 nonmetals as conductors l.jpg
24.1 Nonmetals as conductors complicated than for a simple resistor because there are three variables.

  • In an insulator, the electrons are tightly bonded to atoms and cannot move.

  • Since the electrons cannot move, they cannot carry current.


24 1 semiconductors15 l.jpg
24.1 Semiconductors complicated than for a simple resistor because there are three variables.

  • The electrons in a semiconductor are also bound to atoms, but the bonds are relatively weak.

  • The density of free electrons is what determines the conductivity of a semiconductor.


24 1 semiconductors16 l.jpg
24.1 Semiconductors complicated than for a simple resistor because there are three variables.

  • If there are many free electrons to carry current, the semiconductor acts more like a conductor.

  • If there are few electrons, the semiconductor acts like an insulator.

  • Silicon is the most commonly used semiconductor.

  • Atoms of silicon have 14 electrons.

  • Ten of the electrons are bound tightly inside the atom.

  • Four electrons are near the outside of the atom and only loosely bound.


24 1 changing conductivity l.jpg
24.1 Changing conductivity complicated than for a simple resistor because there are three variables.

  • Anything that changes the number of free electrons has a huge effect on conductivity in a semiconductor.

  • Adding a phosphorus impurity to silicon increases the number of electrons that can carry current.

  • Silicon with a phosphorus impurity makes an n-type semiconductor with current of negative charge.


24 1 changing conductivity18 l.jpg
24.1 Changing conductivity complicated than for a simple resistor because there are three variables.

  • When a small amount of boronis mixed into silicon the opposite effect happens.

  • When an electron is taken by a boron atom, the silicon atom is left with a positive charge and current is carried as electrons move.

  • Silicon with a boron impurity is a p-type semiconductor.


24 1 the p n junction l.jpg
24.1 The p-n junction complicated than for a simple resistor because there are three variables.

  • A p-n junction forms where p-type and n-type semiconductor materials meet.

  • The depletion region becomes an insulating barrier to the flow of current because electrons and holes have combined to make neutral silicon atoms.


24 1 the physics of diodes l.jpg

The complicated than for a simple resistor because there are three variables.depletion region of a p-n junction is what gives diodes, transistors, and all other semiconductors their useful properties.

24.1 The physics of diodes


24 1 the physics of diodes21 l.jpg

As the voltage increases, no current can flow because it is blocked by a larger (insulating) depletion region.

24.1 The physics of diodes


24 1 the physics of diodes22 l.jpg

If the opposite voltage is applied, both electrons and holes are repelled towardthe depletion region.

As a result, the depletion region gets smaller.

Once the depletion region is gone, electrons are free to carry current across the junction and the semiconductor becomes a conductor.

24.1 The physics of diodes


24 1 the physics of diodes23 l.jpg

In short, a p-n junction is a diode. are repelled

The p-njunction blocksthe flow of current from the n side to the p side.

The p-njunction allowscurrent to flow from the p side to the n side if the voltage difference is more than 0.6 volts.

24.1 The physics of diodes


24 1 the physics of transistors l.jpg

A transistor is made from two are repelled p-n junctions back to back.

An npntransistor has a p-type layer sandwiched between two n-type layers.

A pnptransistor is the inverse.

An n-type semiconductor is between two layers of p-type.

24.1 The physics of transistors


24 2 circuits with diodes and transistors l.jpg
24.2 Circuits with diodes and transistors are repelled

  • A diode can convert alternating current electricity to direct current.

  • When the AC cycle is positive, the voltage passes through the diode because the diode is conducting and has low resistance.

  • A single diode is called a halfwave rectifiersince it converts half the AC cycle to DC.


24 2 circuits with diodes and transistors26 l.jpg
24.2 Circuits with Diodes and Transistors are repelled

  • When 4 diodes are arranged in a circuit, the whole AC cycle can be converted to DC and this is called a full-wave rectifier.


24 2 ac into dc l.jpg

A bridge-rectifier circuit are repelled uses the entire AC cycle by inverting the negative portions.

This version of the full-wave rectifier circuit is in nearly every AC adapter you have ever used.

24.2 AC into DC


24 2 a transistor switch l.jpg

In many electronic circuits a small voltage or current is used to switch a much larger voltage or current.

Transistors work very well for this application because they behave like switches that can be turned on and off electronicallyinstead of using manual or mechanical action.

24.2 A transistor switch


24 2 a transistor switch29 l.jpg

When the current into the base is zero, a transistor has a resistance of 100,000 ohms or more.

When a tiny current flows into the base, the resistance drops to 10 ohms or less.

24.2 A transistor switch


24 2 a transistor switch30 l.jpg

The resistance difference between “on” and “off” for a transistor switch is good enough for many useful circuits such as an indicator light bulb in a mechanical circuit.

24.2 A transistor switch


24 2 a transistor amplifier l.jpg

One of the most important uses of a transistor is to a amplify a signal.

In electronics, the word “amplify” means to make the voltage or current of the input signal larger without changing the shape of the signal.

24.2 A transistor amplifier


24 2 a transistor amplifier32 l.jpg

In an amplifier circuit, the transistor is not switched fully “on” like it is in a switching circuit.

Instead, the transistor operates partially on and its resistance varies between a few hundred ohms and about 10,000 ohms, depending on the specific transistor.

24.2 A transistor amplifier


24 2 electronic logic l.jpg
24.2 Electronic Logic fully “on” like it is in a switching circuit.

  • Logic circuits are designed to compare inputs and produce specific output when all the input conditions are met.

  • Logic circuits assign voltages to the two logical conditions of TRUE (T) and FALSE (F).

  • For example, the circuit that starts your car only works when a) the car is in park, b) the brake is on, and c) the key is turned.


24 2 electronic logic34 l.jpg
24.2 Electronic Logic fully “on” like it is in a switching circuit.

  • There is one output which starts the car if TRUE and does not start the car if FALSE.


24 2 a transistor logic circuit l.jpg

The only way for the output to be 3 V is when all three transistors are on, which only happens if all three inputs are TRUE.

24.2 A transistor logic circuit


24 2 circuits with diodes and transistors36 l.jpg

Key Question: transistors are on, which only happens if all three inputs are

What are some useful properties of transistors?

24.2 Circuits with Diodes and Transistors

*Students read Section 24.2 BEFORE Investigation 24.2


24 3 digital electronics l.jpg
24.3 Digital Electronics transistors are on, which only happens if all three inputs are

  • A signal is anything that carries information.

  • Today the word signal usually means a voltage, current, or light wave that carries information.

  • A microphone converts the variations in air pressure from the sound wave into variations in voltage in an analog electrical signal.


24 3 digital electronics38 l.jpg
24.3 Digital Electronics transistors are on, which only happens if all three inputs are

  • A digital signal can only be on or off.

  • A digital signal is very different from an analog signal.


24 3 digital electronics39 l.jpg
24.3 Digital Electronics transistors are on, which only happens if all three inputs are

  • Digital signals can send billions of ones and zeros per second, carrying more information than analog signals.


24 3 digital electronics40 l.jpg
24.3 Digital Electronics transistors are on, which only happens if all three inputs are

  • Digital signals are also easier to store, process, and reproduce than analog signals.


24 3 digital electronics41 l.jpg
24.3 Digital Electronics transistors are on, which only happens if all three inputs are


24 3 computers l.jpg

A transistors are on, which only happens if all three inputs are computer is an electronic device for processing digital information.

All computers have three key systems:

memory

central processing unit, or cpu

input-output system or I/O

24.3 Computers


24 3 computers43 l.jpg

Circuits called transistors are on, which only happens if all three inputs are logic gates are the basic building blocks of computers and almost all digital systems.

The fundamental logic gates are called AND, OR, NAND,and NOR.

24.3 Computers


24 3 computers44 l.jpg

Logic gates transistors are on, which only happens if all three inputs are are built from many transistors in integrated circuits, commonly known as “chips.”

As their names imply, these gates compare two input voltages and produce an output voltage based on the inputs.

24.3 Computers


24 3 computers45 l.jpg

This logic circuit compares two four-bit electronic numbers. transistors are on, which only happens if all three inputs are

The output of this circuit will be four ones (3V on each) only if the number entered by the keyboard exactly matches the number in the computer’s memory.

24.3 Computers


24 3 digital electronics46 l.jpg

Key Question: transistors are on, which only happens if all three inputs are

How do you construct electronic logic circuits?

24.3 Digital Electronics

*Students read Section 24.3 BEFORE Investigation 24.3


Application electronic addition of two numbers l.jpg
Application: Electronic Addition of Two Numbers transistors are on, which only happens if all three inputs are


ad