Sabado, Nobyembre 7, 2015

Logic Gates

Caupayan, Jedda Anne G.                                                                                                                            BSEd-4
                               
Logic Gate

I.                    Definition


In a digital circuit, logic gates can be found and those serve as digital systems’ elementary building block.  Most of the logic gates have one output and two inputs. The logic gates are AND, OR, NOT, NAND, NOR, EXOR and EXNOR gates. At any given moment, every terminal is in one of the two binary conditions low (0) or high (1), represented by different voltage levels.

II.                    Types

1.       AND Gate 



The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high.  A dot (.) is used to show the AND operation i.e. A.B.  Bear in mind that this dot is sometimes omitted i.e. AB

                 2.       OR Gate 



     The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high.  A plus (+) is used to show the OR operation.
                       
                
                     3. NOT gate


 
The NOT gate is an electronic circuit that produces an inverted version of the input at its output.  It is also known as an inverter.  If the input variable is A, the inverted output is known as NOT A.  This is also shown as A', or A with a bar over the top, as shown at the outputs.The diagrams below show two ways that the NAND logic gate can be configured to produce a NOT gate. It can also be done using NOR logic gates in the same way.



4.       NAND Gate




This is a NOT-AND gate which is equal to an AND gate followed by a NOT gate.  The outputs of all NAND gates are high if any of the inputs are low. The symbol is an AND gate with a small circle on the output. The small circle represents inversion.

5.       NOR Gate




This is a NOT-OR gate which is equal to an OR gate followed by a NOT gate.  The outputs of all NOR gates are low if any of the inputs are high. The symbol is an OR gate with a small circle on the output. The small circle represents inversion.

6.       EXOR Gate



The 'Exclusive-OR' gate is a circuit which will give a high output if either, but not both, of its two inputs are high.  An encircled plus sign () is used to show the EOR operation.

7.       EXNOR Gate




The 'Exclusive-NOR' gate circuit does the opposite to the EOR gate. It will give a low output if either, but not both, of its two inputs are high. The symbol is an EXOR gate with a small circle on the output. The small circle represents inversion.

III.                    Logic Gate Symbols



IV.                    Applications

         1.       Burglar alarm

           When the switch is closed one input of the NAND gate is LOW. When the LDR is in the light the other input is LOW. This means that if either of these things happen, i.e. the switch is closed or the light is on one of the inputs is LOW, the output is HIGH and the buzzer sounds..         
Retrieved from: http://goo.gl/UTXrcV

            2.       Freezer warning buzzer
When the thermistor is COLD its resistance is LARGE and the input to the NAND gate is high.
Since the NAND gate is connected as an INVERTER the output is LOW.
As the thermistor warms up its resistance decreases, the voltage across it falls and the input to the NAND gate falls.
When it becomes low enough the output becomes HIGH and the buzzer sounds.

Retrieved from: http://goo.gl/UTXrcV


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Transistors

Caupayan. Jedda Anne G.                                                                                         BSEd-4

Transistors
I.        Introduction

Do you wonder how hearing aid works? Do you also wonder when we use a microphone; everybody in the group can hear us? Well it is all about electronics specifically transistors.



Retrieved from: https://goo.gl/tDFEpY

I.        Definition

Transistors are active components and are found everywhere in electronic circuits. They are made from silicon a chemical element found in sand which does not normally conduct electricity. Transistor has two types the Bipolar Junction Transistors and Field Effect Transistors. It is also a semiconductor device that has three connections.

I.        History
Transistors were invented at Bell Laboratories in New Jersey in 1947 by three brilliant US physicists: John Bardeen (1908–1991), Walter Brattain (1902–1987), and William Shockley (1910–1989).


Retrieved from: https://goo.gl/IdYh3F

I.        Types of Transistors

1.      Bipolar Junction Transistors
-are transistors which are made up of 3 regions, the base, the collector, and the emitter.
                  -Current-controlled devices
                  -come in two main types, NPN and PNP


Retrieved from: https://goo.gl/IIP9K2

a. NPN transistor      -is one in which the majority current carrier are electrons.
b. PNP transistor      -the majority current carrier are holes.



Retrieved from: https://goo.gl/QiDuSx 

Transistors are manufactured in different shapes but they have three leads (legs). 
i. BASE                 - the lead responsible for activating the transistor
ii. COLLECTOR    - the positive lead
iii. EMITTER                      - the negative lead
2. Field Effect Transistors
                  - are transistors which are made up of 3 regions, a gate, a source, and a drain    



Retrieved from: https://goo.gl/Pb1Iuz
  
They are used as:      

  1. Amplifiers                 
As amplifiers, they are used in high and low frequency stages, oscillators, modulators, detectors and in any circuit needing to perform a function.
2. Switching devices     

            In digital circuits they are used as switches

I.        Applications
1.      Microphone

Retrieved from: https://goo.gl/v1auuQ

a.      A transistor can be used to amplify current. This is because a small change in base current causes a large change in collector current.
b.      Example is a microphone.
c.      Sound waves that are fed into the microphone cause the diaphragm in the microphone to vibrate.
d.      The electrical output of the microphone changes according to the sound waves.
e.      As a result, the base current is varying because of the small alternating voltage produced by the microphone.
f.        A small change in the base current causes a large change in the collector current.
g.      The varying collector current flows into the loudspeaker. There, it is changed into the sound waves corresponding to the original sound waves.
h.      The frequencies of both waves are equivalent but the amplitude of the sound wave from the loudspeaker is higher than the sound waves fed into the microphone.

2.      Headphone

Retrieved from: https://goo.gl/B6O86g

3.      Hearing Aids

Retrieved from: https://goo.gl/QFZV6f


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Huwebes, Oktubre 29, 2015

Integrated Circuits

Caupayan.JeddaAnne G.                                                                                                                            BSEd-4
Integrated Circuits
I.                    Introduction

We already know much about some of the components of a circuit lie resistors, capacitors and transistors. In this chapter you will learn about a circuit that has those three electronic devices. This chapter includes the definition integrated circuit its types and applications.


Figure 1: Integrated Circuit
Retrieved from: https://goo.gl/clR1u5

I.                    Definition

Integrated circuit is also known as micro chip or chip. It is a semiconductor that is composed of millions of resistors, capacitors and transistors. They said that integrated circuit is the keystone of modern electronics. It is also the heart and brain of most circuits because it can be found on every circuit board. All those electronic devices that is present in an integrated circuit are connected together to achieve a common goal and that is to be an amplifier, oscillator, timer, counter, computer memory or micro processor. IC is categorized into two, the linear or analog and digital. They can be used depending on its intended application.

Figure2: The guts of an integrated circuit, visible after removing the top.

Retrieved from: https://goo.gl/clR1u5

II.                    Types of Integrated Circuit

     1.       Linear Integrated Circuit (Analog)
-has a variable output that is continuous that depends on the input signal level
-the output signal level is a linear function of the input signal level, it means that when the instantaneous output is graphed against the instantaneous input, the plot appears as a straight line
-it is used as audio-frequency and radio frequency amplifiers

Figure 3: Linear IC
Retrieved from: https://goo.gl/GUFDu7

        2.       Digital Integrated Circuit
-can be seen and used only at few defined levels or states rather that a continuous range of signal amplitudes
-its fundamental building blocks are logic gates which work with binary data that is signals that have only two different states, called low (logic 0) and high (logic 1)

Figure 4: Digital IC
Retrieved from: https://goo.gl/VT7NkR

III.                   Applications
       Integrated circuits are used in computers, digital clock, timer, counter, and etc. 

Figure 5: Digital clock

Retrieved from: https://goo.gl/XNuxOm


Figure 6: Computer
Retrieved from: https://goo.gl/A325at


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Semiconductors

Caupayan,JeddaAnne G.                                                                                                                            BSEd-4
                                                                                Semiconductors
I.                    Introduction

Our prior knowledge tells us that conductors are materials that allow the flow of electric current in one or more directions. We also know that insulators cannot conduct electricity but there is a certain material that can be partly an insulator and conductor and that is semiconductor. This chapter will tell us about semiconductor, its types and applications.

II.                  Definition
Semiconductors are materials whose ability to conduct electricity falls somewhere between that an insulator and that of a conductor. Those are actually solid chemical elements that can conduct electricity under some conditions but not others, making it a good material for the control of electrical current. Semiconductors are used for electrical devices because their material characteristics can be changed significantly through the process called doping. Doping is s process of adding very small amounts of selected conductive additives called impurities to semiconductors. It can increase the number of free charges. When an impurity increases the number of free electrons, the doped semiconductor is negative or n-type, but when it reduces, causing more holes, it creates appositive or p-type semiconductor.
III.                Types of Semiconductors
1.       1. Intrinsic semiconductor
-a chemically very pure and possesses poor conductivity

-has equal number of carriers (electrons) and positive carriers (holes)
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   2.   Extrinsic semiconductor
-improved intrinsic by a certain process called doping, which alters chemical properties of semiconductors

a.       N-type
-majority carriers are electrons and minority carriers are holes
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a.       P-type
-majority carriers are holes and minority carriers are electrons
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I.                    Applications
1.       Semiconductor diodes
-these can be made by doping crystal of pure germanium (or silicon) to create a region of n-type

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a                                 a. Forward- biased
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                                  b.    Reversed-biased
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              2.       Semiconductors in photocopiers

-the photoconductors found in photocopiers are said to semiconductors


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