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Complete Guide for Tech Beginners (part-2)



Complete Guide for Tech Beginners (part-2) 
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Step 7: Capacitor


A capacitor is a bit like a battery, but it has a different job to do. A battery uses chemicals to store electrical energy and release it very slowly through a circuit; sometimes (in the case of a quartz watch) it can take several years. A capacitor generally releases its energy much more rapidly—often in seconds or less. If you're taking a flash photograph, for example, you need your camera to produce a huge burst of light in a fraction of a second. A capacitor attached to the flash gun charges up for a few seconds using energy from your camera's batteries. (It takes time to charge a capacitor and that's why you typically have to wait a little while.) Once the capacitor is fully charged, it can release all that energy in an instant through the xenon flash bulb. Zap!

There are many different kinds of capacitors available from very small capacitor beads used in resonance circuits to large power factor correction capacitors, but they all do the same thing, they store charge. In its basic form, a Capacitor consists of two or more parallel conductive (metal) plates which are not connected or touching each other, but are electrically separated either by air or by some form of a good insulating material such as waxed paper, mica, ceramic, plastic or some form of a liquid gel as used in electrolytic capacitors. The insulating layer between capacitors plates is commonly called the Dielectric. A Typical Capacitor
Due to this insulating layer, DC current cannot flow through the capacitor as it blocks it allowing instead a voltage to be present across the plates in the form of an electrical charge.
Capacitors and capacitance
The amount of electrical energy a capacitor can store is called its capacitance. The capacitance of a capacitor is a bit like the size of a bucket: the bigger the bucket, the more water it can store; the bigger the capacitance, the more electricity a capacitor can store. There are three ways to increase the capacitance of a capacitor. One is to increase the size of the plates. Another is to move the plates closer together. The third way is to make the dielectric as good an insulator as possible. Capacitors use dielectrics made from all sorts of materials. In transistor radios, the tuning is carried out by a large variable capacitor that has nothing but air between its plates. In most electronic circuits, the capacitors are sealed components with dielectrics made of ceramics such as mica and glass, paper soaked in oil, or plastics such as mylar.
The size of a capacitor is measured in units called farads (F), named for English electrical pioneer Michael Faraday (1791–1867). One farad is a huge amount of capacitance so, in practice, most of the capacitors we come across are just fractions of a farad—typically micro farads (millionths of a farad, written μF), nano farads (thousand-millionths of a farad written nF), and pico farads (million millionths of a farad, written pF).Super capacitors store far bigger charges, sometimes rated in thousands of farads.

Types of Capacitors

There are many different types of capacitors and they each vary in their characteristics and each have their own advantages and disadvantages.
Some types of capacitors can charge up to higher voltages and, thus, can be used in high voltage applications. Some capacitors can charge up to very high charges, such as aluminum electrolytic capacitors. Some capacitors have very low leakage low leakage rates and others have very high leakage rates. All of these factors determine how and in what application each of the capacitors will be used in circuits.
Based on the design, capacitors are categorized in these different types: 

Electrolytic type:

For most of applications we use Electrolytic type Capacitors. They are very important for an electronic student as they are easy to get and to use, and they are inexpensive too.
Electrolytic Capacitors are generally used when very large capacitance values are required typically above 1μF. Here instead of using a very thin metallic film layer for one of the electrodes, a semi-liquid electrolyte solution in the form of a jelly or paste is used which serves as the second electrode (usually the cathode).
The dielectric is a very thin layer of oxide which is grown electro-chemically in production with the thickness of the film being less than ten microns. This insulating layer is so thin that it is possible to make capacitors with a large value of capacitance for a small physical size as the distance between the plates, d is very small.
The majority of electrolytic types of capacitors are Polarized, that is the DC voltage applied to the capacitor terminals must be of the correct polarity, i.e. positive to the positive terminal and negative to the negative terminal as an incorrect polarization will break down the insulating oxide layer and permanent damage may result. All polarized electrolytic capacitors have their polarity clearly marked with a negative sign to indicate the negative terminal and this polarity must be followed. Electrolytic Capacitors are generally used in DC power supply circuits due to their large capacitance’s and small size to help reduce the ripple voltage or for coupling and decoupling applications. One main disadvantage of electrolytic capacitors is their relatively low voltage rating and due to the polarization of electrolytic capacitors, it follows then that they must not be used on AC supplies. Electrolytic’s generally come in two basic forms; Aluminium Electrolytic Capacitors and Tantalum Electrolytic Capacitors.
An electrolytic capacitor is usually labeled with these things:
1. Capacitance value.
2. Maximum voltage.
3. Maximum temperature.
4. Polarity.
For an electrolytic capacitor, the capacitance is measured in micro Farad. Based on requirement the appropriate capacitor is chosen. With higher capacitance, the size of capacitor also increases.

Voltage Rating of a Capacitor

All capacitors have a maximum voltage rating and when selecting a capacitor consideration must be given to the amount of voltage to be applied across the capacitor. The maximum amount of voltage that can be applied to the capacitor without damage to its dielectric material is generally given in the data sheets as: WV, (working voltage) or as WV DC, (DC working voltage). If the voltage applied across the capacitor becomes too great, the dielectric will break down (known as electrical breakdown) and arcing will occur between the capacitor plates resulting in a short-circuit. The working voltage of the capacitor depends on the type of dielectric material being used and its thickness. The DC working voltage of a capacitor is just that, the maximum DC voltage and NOT the maximum AC voltage as a capacitor with a DC voltage rating of 100 volts DC cannot be safely subjected to an alternating voltage of 100 volts. Since an alternating voltage has an r.m.s. value of 100 volts but a peak value of over 141 volts!. Then a capacitor which is required to operate at 100 volts AC should have a working voltage of at least 200 volts. In practice, a capacitor should be selected so that its working voltage either DC or AC should be at least 50 percent greater than the highest effective voltage to be applied to it.

Polyester type:


Polyester capacitors are capacitors composed of metal plates with polyester film between them, or a metallised film is deposited on the insulator.
Polyester capacitors are available in the range of 1nF to 15µF, and with working voltages from 50V to 1500V. They come with the tolerance ranges of 5%, 10%, and 20%. They have a high temperature coefficient. They have high isolation resistance, so they are good choice capacitors for coupling and/or storage applications. Compared with most other types, polyester capacitors have high capacitance per unit volume. This means more capacitance can fit into a physically smaller capacitor. This feature, together with their relatively low price makes polyester capacitors a widely used, popular, and cheap capacitor.

Tantalum type:


Tantalum Capacitors are capacitors that are made of tantalum pentoxide. Tantalum capacitors, just like aluminum, are electrolytic capacitors, which means they are polarized. Their main advantages (especially over aluminum capacitors) is that they are smaller, lighter, and more stable. They have lower leakage rates and less inductance between leads. However, their disadvantags are they have a lower maximum capacitance storage and lower maximum working voltage. They are also more prone to damage from high current spikes. For the last reason, tantalum capacitors are used mostly in analog signal systems that lack high current-spike noise.
Ceramic Capacitors:
Ceramic Capacitors or Disc Capacitors as they are generally called, are made by coating two sides of a small porcelain or ceramic disc with silver and are then stacked together to make a capacitor. For very low capacitance values a single ceramic disc of about 3-6mm is used. Ceramic capacitors have a high dielectric constant (High-K) and are available so that relatively high capacitance’s can be obtained in a small physical size. Ceramic Capacitor
They exhibit large non-linear changes in capacitance against temperature and as a result are used as de-coupling or by-pass capacitors as they are also non-polarized devices. Ceramic capacitors have values ranging from a few picofarads to one or two microfarads, ( μF ) but their voltage ratings are generally quite low. Ceramic types of capacitors generally have a 3-digit code printed onto their body to identify their capacitance value in pico-farads. Generally the first two digits indicate the capacitors value and the third digit indicates the number of zero’s to be added. For example, a ceramic disc capacitor with the markings 103 would indicate 10 and 3 zero’s in pico-farads which is equivalent to 10,000 pF or 10nF. Likewise, the digits 104 would indicate 10 and 4 zero’s in pico-farads which is equivalent to 100,000 pF or 100nF and so on. So on the image of the ceramic capacitor above the numbers 154 indicate 15 and 4 zero’s in pico-farads which is equivalent to 150,000 pF or 150nF or 0.15uF. Letter codes are sometimes used to indicate their tolerance value such as: J = 5%, K = 10% or M = 20% etc.

General uses of Capacitors

Smoothing, especially in power supply applications which required converting the signal from AC to DC.
Storing Energy.
Signal decoupling and coupling as a capacitor coupling that blocks DC current and allow AC current to pass in circuits.
Tuning, as in radio systems by connecting them to LC oscillator and for tuning to the desired frequency.
Timing, due to the fixed charging and discharging time of capacitors.
For electrical power factor correction and many more applications.

Step 8: Inductor


An inductor is a passive electronic component that stores energy in the form of a magnetic field. As we know resistor resists the flow of current, inductor resists the change in flowing current through it. So for dc current inductor is nothing but like a conductor. In other words, inductors resist or oppose changes of current but will easily pass a steady state DC current.
The current that flows through an inductor produces a magnetic flux that is proportional to it. But unlike a Capacitor which oppose a change of voltage across their plates, an inductor opposes the rate of change of current flowing through it due to the buildup of self-induced energy within its magnetic field.


In its most basic form, an Inductor is nothing more than a coil of wire wound around a central core. For most coils the current, flowing through the coil produces a magnetic flux around it that is proportional to this flow of electrical current.
The Inductor also called a choke. Inductors are formed with wire tightly wrapped around a solid central core which can be either a straight cylindrical rod or a continuous loop or ring to concentrate their magnetic flux. The schematic symbol for a inductor is that of a coil of wire so therefore, a coil of wire can also be called an Inductor. Inductors usually are categorized according to the type of inner core they are wound around, for example, hollow core (free air), solid iron core or soft ferrite core with the different core types being distinguished by adding continuous or dotted parallel lines next to the wire coil as shown below.
The standard unit of inductance is the henry, abbreviated H. This is a large unit. More common units are the microhenry, abbreviated µH (1 µH =10^-6H) and the millihenry, abbreviated mH (1 mH =10^-3 H). Occasionally, the nanohenry (nH) is used (1 nH = 10^-9 H).
Applications of Inductors

Filters

Inductors are used extensively with capacitors and resistors to create filters for analog circuits and in signal processing. Alone, an inductor functions as a low-pass filter, since the impedance of an inductor increases as the frequency of a signal increases. When combined with a capacitor, whose impedance decreases as the frequency of a signal increase, a notched filter can be made that only allows a certain frequency range to pass through. By combining capacitors, inductors, and resistors in a number of ways advanced filter topologies can be created for any number of applications. Filters are used in most electronics, although capacitors are often used rather than inductors when possible since they are smaller and cheaper.
Sensors

Con tactless sensors are prized for their reliability and ease of operation and inductors can be used to sense magnetic fields or the presence of magnetically permeable material from a distance. Inductive sensors are used at nearly every intersection with a traffic light to detect the amount of traffic and adjust the signal accordingly. These sensors work exceptionally well for cars and trucks, but some motorcycles and other vehicles do not have enough of a signature to be detected by the sensors without a little extra boost by adding a h3 magnet to the bottom of the vehicle. Inductive sensors are limited in two major ways, either the object to be sensed must be magnetic and induce a current in the sensor or the sensor must be powered to detect the presence of materials that interact with a magnetic field. This limits the applications of inductive sensors and has a major impact on designs that use them.
Transformers

Combining inductors that have a shared magnetic path will form a transformer. The transformer is a fundamental component of national electrical grids and found in many power supplies as well to increase or decrease voltages to a desired level. Since magnetic fields are created by a change in current, the faster the current changes (increase in frequency) the more effective a transformer operates. Of course, as the frequency of the input increases, the impedance of the inductor begins to limit the effectiveness of a transformer.
Motors

Normally inductors are in a fixed position and not allowed to move to align themselves with any nearby magnetic field. Inductive motor leverage the magnetic force applied to inductors to turn electrical energy in to mechanical energy. Inductive motors are designed so that a rotating magnetic field is created in time with an AC input. Since the speed of rotation is controlled by the input frequency, induction motors are often used in fixed speed applications that can be powered directly from 50/60hz mains power. The biggest advantage of inductive motors over other designs is that no electrical contact is required between the rotor and the motor which makes inductive motors very robust and reliable.
Energy Storage

Like capacitors, inductors can be used for energy storage. Unlike capacitors, inductors have a severe limitation on how long they can store energy since the energy is stored in a magnetic field which collapses quickly once power is removed. The main use for inductors as energy storage is in switch-mode power supplies, like the power supply in a PC. In the simpler, non-isolated switch-mode power supplies, a single inductor is used in place of transformer and energy storage component. In these circuits, the ratio of the time the inductor is powered to the time it is un powered determines the input to output voltage ratio.
Inductors are also used for wireless power transfer and in electro-mechanical relay.

Step 9: Diode


A diode is a specialized electronic component with two electrodes called the anode and the cathode. Most diodes are made with semiconductor materials such as silicon, germanium, or selenium. Diodes can be used as rectifiers, signal limiters, voltage regulators, switches, signal modulators, signal mixers, signal demodulators, and oscillators.
The fundamental property of a diode is its tendency to conduct electric current in only one direction. When the cathode is negatively charged relative to the anode at a voltage greater than a certain minimum called forward break over, then current flows through the diode. If the cathode is positive with respect to the anode, is at the same voltage as the anode, or is negative by an amount less than the forward break over voltage, then the diode does not conduct current. This is a simplistic view, but is true for diodes operating as rectifiers, switches, and limiters. The forward break over voltage is approximately six tenths of a volt (0.6 V) for silicon devices, 0.3 V for germanium devices, and 1 V for selenium devices.
Breakdown Voltage


If a large enough negative voltage is applied to the diode, it will give in and allow current to flow in the reverse direction. This large negative voltage is called the breakdown voltage. Some diodes are actually designed to operate in the breakdown region, but for most normal diodes it’s not very healthy for them to be subjected to large negative voltages. For normal diodes this breakdown voltage is around -50V to -100V, or even more negative.
Types of Diodes
Many different types of diodes today are in use in electronics. The different kinds each have their own specialized uses. I will only discuss about more common types.
Rectifier Diode:

These diodes are used to rectify alternating power inputs in power supplies. A rectifier or power diode is a standard diode with a much higher maximum current rating. This higher current rating usually comes at the cost of a larger forward voltage. The 1N4001, for example, has a current rating of 1A and a forward voltage of 1.1V.
Signal diodes:

A small signal diode is a small non-linear semiconductor which is often used in electronic circuits where high frequencies or small currents are involved in television, radio and digital logic circuits. Small signal diodes are smaller in size compared to regular power diodes. They usually have a medium-high forward voltage drop and a low maximum current rating. A common example of a signal diode is the 1N4148. Very general purpose, it’s got a typical forward voltage drop of 0.72V and a 300mA maximum forward current rating.
Schottky Diodes:

These diodes feature lower forward voltage drop as compared to the ordinary silicon PN junction diodes. The voltage drop may be somewhere between 0.15 and 0.4 volts at low currents, as compared to the 0.6 volts for a silicon diode. In order to achieve this performance, these diodes are constructed differently from normal diodes, with metal to semiconductor contact. Schottky diodes are used in RF applications, rectifier applications and clamping diodes.
Zener diodes:


Zener diodes are the weird outcast of the diode family. They’re usually used to intentionally conduct reverse current. Zener’s are designed to have a very precise breakdown voltage, called the zener breakdown or zener voltage. When enough current runs in reverse through the zener, the voltage drop across it will hold steady at the breakdown voltage. Taking advantage of their breakdown property, Zener diodes are often used to create a known reference voltage at exactly their Zener voltage. They can be used as a voltage regulator for small loads, but they’re not really made to regulate voltage to circuits that will pull significant amounts of current.
Light-Emitting Diodes:

Like normal diodes, LEDs only allow current through one direction. They also have a forward voltage rating, which is the voltage required for them to light up. The VF rating of an LED is usually larger than that of a normal diode (1.2~3V), and it depends on the color the LED emits. For example, the rated forward voltage of a Super Bright Blue LED is around 3.3V, while that of the equal size Super Bright Red LED is only 2.2V. I will discuss about LEDs more detail later.
Photodiode:

Photodiodes are used to detect light and feature wide, transparent junctions. Generally, these diodes operate in reverse bias, wherein even small amounts of current flow, resulting from the light, can be detected with ease. Photodiodes can also be used to generate electricity, used as solar cells and even in photometry.
Laser Diode:

This type of diode is different from the LED type, as it produces coherent light. These diodes find their application in DVD and CD drives, laser pointers, etc. Laser diodes are more expensive than LEDs. However, they are cheaper than other forms of laser generators. Moreover, these laser diodes have limited life.

Step 10: LED



Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.
Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.
The lifespan of an LED surpasses the short life of an incandescent bulb by thousands of hours. Tiny LEDs are already replacing the tubes that light up LCD HDTVs to make dramatically thinner televisions.
LEDs are mostly used for two things: illumination and indication. Illumination means to "shine light onto something" - like a flashlight or headlights. You want your headlights to be bright as heck. Indication mean to "point something out" - like a turn signal or brake lights on a car. You don't want your car's turn signal to blind people! Diffused LEDs are really good at indication, they look soft and uniform and you can see them well from any angle. Clear LEDs are really good at illumination, the light is direct and powerful - but you can't see them well from an angle because the light is only going forward.
LED circuit design

LED's are diodes, which are biased with a current rather than voltage. Simply, when LED's are "fed" with some current in the forward direction (plus to minus, or anode to cathode it would start to emit light at some minimum current. A typical red LED's require about 10mA to 20mA current for decent brightness. Any more may not help much--LED's would be stressed when pushed beyond the limits and may be destroyed.
Since LED's are current devices, a voltage can not be applied directly across it, LED's cannot be connected directly to the battery or power supply. The LED will be instantly destroyed because the current is too great. The current must be reduced. The easiest way to do this is by using a resistor. The resistor will lower the current and drop the voltage down to a manageable level.
So, how do we figure out what value resistor to use? We shall use the ohm's law for this. Ohms law states that voltage is the product of the current and the resistance, or V = IR, where "I" is the current.

Calculate the LED resistor value with the following formula:
LED Resistor Value, R = (supply voltage - LED voltage) / LED current
In our example:

Say we use a 9V battery, then supply voltage = 9V. LED voltage for red LED's, from Step 2 is 2.0 V LED current is 20 mA (this is a typical value if not provided by the manufacturer) If the resistor value is not available, then choose the nearest standard resistor value which is greater. If you want to increase the battery life you can select a higher resistor value to reduce current. The reduced current will result in a dimmer LED. For 15mA led current, R = (9 - 2.0) / 15 mA = 466 ohms, use the next higher standard value = 470 ohms.


Step 11: Transistor



There are two types of basic transistor out there: bi-polar junction (BJT) and metal-oxide field-effect (MOSFET), and there are actually two versions of the BJT: NPN and PNP.
 Most circuits tend to use NPN. There are hundreds of transistors which work at different voltages but all of them fall into these two categories.
Transistors are manufactured in different shapes but they have three leads (legs). The BASE - which is the lead responsible for activating the transistor? The COLLECTOR - which is the positive lead.The EMITTER - which is the negative lead?
A transistor is really simple—and really complex. Let's start with the simple part. A transistor is a miniature electronic component that can do two different jobs. It can work either as an amplifier or a switch:

When it works as an amplifier, it takes in a tiny electric current at one end (an input current) and produces a much bigger electric current (an output current) at the other. In other words, it's a kind of current booster. That comes in really useful in things like hearing aids, one of the first things people used transistors for. A hearing aid has a tiny microphone in it that picks up sounds from the world around you and turns them into fluctuating electric currents. These are fed into a transistor that boosts them and powers a tiny loudspeaker, so you hear a much louder version of the sounds around you.

Transistors can also work as switches. A tiny electric current flowing through one part of a transistor can make a much bigger current flow through another part of it. In other words, the small current switches on the larger one. 

This is essentially how all computer chips work. For example, a memory chip contains hundreds of millions or even billions of transistors, each of which can be switched on or off individually. Since each transistor can be in two distinct states, it can store two different numbers, zero and one. With billions of transistors, a chip can store billions of zeros and ones, and almost as many ordinary numbers and letters (or characters, as we call them). More about this in a moment.
Operation Modes

Unlike resistors, which enforce a linear relationship between voltage and current, transistors are non-linear devices. They have four distinct modes of operation, which describe the current flowing through them. (When we talk about current flow through a transistor, we usually mean current flowing from collector to emitter of an NPN transistor. The four transistor operation modes are:
Saturation – The transistor acts like a short circuit. Current freely flows from collector to emitter.
Cut-off – The transistor acts like an open circuit. No current flows from collector to emitter.
Active – The current from collector to emitter is proportional to the current flowing into the base.
Reverse-Active – Like active mode, the current is proportional to the base current, but it flows in reverse.
Applications: Switches
Image result for transistor Applications: Switches
One of the most fundamental applications of a transistor is using it to control the flow of power to another part of the circuit – using it as an electric switch. Driving it in either cutoff or saturation mode, the transistor can create the binary on/off effect of a switch. Transistor switches are critical circuit-building blocks; they’re used to make logic gates, which go on to create microcontrollers, microprocessors, and other integrated circuits.
Transistor Switch

Let’s look at the most fundamental transistor-switch circuit: an NPN switch. Here we use an NPN to control a high-power LED.
Our control input flows into the base, the output is tied to the collector, and the emitter is kept at a fixed voltage.
While a normal switch would require an actuator to be physically flipped, this switch is controlled by the voltage at the base pin. A microcontroller I/O pin, like those on an Arduino, can be programmed to go high or low to turn the LED on or off.
When the voltage at the base is greater than 0.6V (or whatever your transistor’s Vth might be), the transistor starts saturating and looks like a short circuit between collector and emitter. When the voltage at the base is less than 0.6V the transistor is in cutoff mode – no current flows because it looks like an open circuit between C and E.
The circuit above is called a low-side switch, because the switch – our transistor – is on the low (ground) side of the circuit. Alternatively, we can use a PNP transistor to create a high-side switch:
Similar to the NPN circuit, the base is our input, and the emitter is tied to a constant voltage. This time however, the emitter is tied high, and the load is connected to the transistor on the ground side.
This circuit works just as well as the NPN-based switch, but there’s one huge difference: to turn the load “on” the base must be low. This can cause complications, especially if the load’s high voltage (VCC in this picture) is higher than our control input’s high voltage. For example, this circuit wouldn’t work if you were trying to use a 5V-operating Arduino to switch on a 12V motor. In that case it’d be impossible to turn the switch off because VB would always be less than VE.
Base Resistors

You’ll notice that each of those circuits uses a series resistor between the control input and the base of the transistor. Don’t forget to add this resistor! A transistor without a resistor on the base is like an LED with no current-limiting resistor.
Recall that, in a way, a transistor is just a pair of interconnected diodes. We’re forward-biasing the base-emitter diode to turn the load on. The diode only needs 0.6V to turn on, more voltage than that means more current. Some transistors may only be rated for a maximum of 10-100mA of current to flow through them. If you supply a current over the maximum rating, the transistor might blow up.
The series resistor between our control source and the base limits current into the base. The base-emitter node can get its happy voltage drop of 0.6V, and the resistor can drop the remaining voltage. The value of the resistor, and voltage across it, will set the current.
The resistor needs to be large enough to effectively limit the current, but small enough to feed the base enough current. 1mA to 10mA will usually be enough and base resistor value may be 1k to 10k, but check your transistor’s datasheet to make sure.
Some common BJTs frequently used in hobbyist project
Name
Type
Vce
Ic
Pd
ft
2N2222
NPN
40V
800mA
625mW
300MHz
BC548
NPN
30V
100mA
500mW
300MHz
2N3904
NPN
40V
200mA
625mW
270MHz
2N3906
PNP
-40V
-200mA
625mW
250MHz
BC557
PNP
-45V
-100mA
500mW
150MHz
TIP120 (power)
NPN
60V
5A
65W
-
Please check the datasheet for details.
MOSFET

The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is another type of transistor used for amplifying or switching electronic signals.
The main advantage of a MOSFET over a regular transistor is that it requires very little current to turn on (less than 1mA), while delivering a much higher current to a load (10 to 50A or more).
The Metal Oxide Semiconductor Field Effect Transistor, or MOSFET for short, has an extremely high input gate resistance with the current flowing through the channel between the source and drain being controlled by the gate voltage. Because of this high input impedance and gain, MOSFETs can be easily damaged by static electricity if not carefully protected or handled.
MOSFET’s are ideal for use as electronic switches or as common-source amplifiers as their power consumption is very small. Typical applications for metal oxide semiconductor field effect transistors are in Microprocessors, Memories, Calculators and Logic CMOS Gates etc

Step 12: Voltage Regulators

A voltage regulator generates a fixed output voltage of a preset magnitude that remains constant regardless of changes to its input voltage or load conditions. There are two types of voltage regulators:

·         Linear
·         Switching
The linear regulator's power dissipation is directly proportional to its output current for a given input and output voltage, so typical efficiencies can be 50% or even lower. Using the optimum components, a switching regulator can achieve efficiencies in the 90% range. However, the noise output from a linear regulator is much lower than a switching regulator with the same output voltage and current requirements. Typically, the switching regulator can drive higher current loads than a linear regulator.


A linear regulator employs an active (BJT or MOSFET) pass device (series or shunt) controlled by a high gain differential amplifier. It compares the output voltage with a precise reference voltage and adjusts the pass device to maintain a constant output voltage.
This regulating device acts like a variable resistor and continuously adjusts the voltage divider network in order to maintain an output voltage which is constant. The difference between the input voltage and regulated voltage is continually dissipating as waste heat. Due to linear voltage regulators being often used in several electronic devices, linear regulators in integrated circuit (IC) form are very common. There are several different kinds of linear regulators.
All linear regulators require an input voltage at least some minimum amount higher than the desired output voltage. That minimum amount is called the dropout voltage. For example, a common regulator such as the 7805 has an output voltage of 5V, but can only maintain this if the input voltage remains above about 7V, before the output voltage begins sagging below the rated output. Its dropout voltage is therefore 7V − 5V = 2V. There are two types of linear regulator:
Fixed regulators

"Fixed" three-terminal linear regulators are commonly available to generate fixed voltages of plus 3 V, and plus or minus 5 V, 6V, 9 V, 12 V, or 15 V, when the load is less than 1.5 A. The "78xx" series (7805, 7812, etc.) regulate positive voltages while the "79xx" series (7905, 7912, etc.) regulate negative voltages. Often, the last two digits of the device number are the output voltage (e.g., a 7805 is a +5 V regulator, while a 7915 is a −15 V regulator). There are variants on the 78xx series ICs, such as 78L and 78S, some of which can supply up to 2 Amps.
Variable regulators

An adjustable regulator generates a fixed low nominal voltage between its output and its adjust terminal (equivalent to the ground terminal in a fixed regulator). This family of devices includes low power devices like LM723 and medium power devices like LM317 and L200. Some of the variable regulators are available in packages with more than three pins, including dual in-line packages. They offer the capability to adjust the output voltage by using external resistors of specific values.
The LM317 series (+1.25V) regulates positive voltages while the LM337 series (−1.25V) regulates negative voltages. The adjustment is performed by constructing a potential divider with its ends between the regulator output and ground, and its centre-tap connected to the 'adjust' terminal of the regulator. The ratio of resistances determines the output voltage using the same feedback mechanisms described earlier.
Commonly used linear voltage regulator
L7805 (Voltage Regulator - 5V): This is the basic L7805 voltage regulator, a three-terminal positive regulator with a 5V fixed output voltage. This fixed regulator provides a local regulation, internal current limiting, thermal shut-down control, and safe area protection for your project. Each one of these voltage regulators can output a max current of 1.5A.
L7812 (Voltage Regulator - 12V): This is the basic L7812 voltage regulator, a three-terminal positive regulator with a 12V fixed output voltage. This fixed regulator provides a local regulation, internal current limiting, thermal shut-down control, and safe area protection for your project. Each one of these voltage regulators can output a max current of 1.5A.
LM317 (Adjustable 1.25V to 37V): TheLM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than1.5 A over an output-voltage range of 1.25 V to 37V. It requires only two external resistors to set the output voltage. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%. It includes current limiting, thermal overload protection, and safe operating area protection.
Please check datasheet for details.
Switching regulator
A switching regulator converts the dc input voltage to a switched voltage applied to a power MOSFET or BJT switch. The filtered power switch output voltage is fed back to a circuit that controls the power switch on and off times so that the output voltage remains constant regardless of input voltage or load current changes.
There are three common topologies: buck (step-down), boost (step-up) and buck-boost (step-up/stepdown). Other topologies include the flyback, SEPIC, Cuk, push-pull, forward, full-bridge, and half-bridge topologies.
Switching regulators require a means to vary their output voltage in response to input and output voltage changes. One approach is to use PWM that controls the input to the associated power switch, which controls its on and off time (duty cycle). In operation, the regulator's filtered output voltage is fed back to the PWM controller to control the duty cycle. If the filtered output tends to change, the feedback applied to the PWM controller varies the duty cycle to maintain a constant output voltage.
Boost converter
A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage greater than its input voltage. Boost converters are used when it required higher voltage than available voltage from battery. Suppose you have a 3.7 V battery but you need 5 V for your device then you can use boost converter.
Because of the ease with which boost converters can supply large over voltages, they will almost always include some regulation to control the output voltage, and there are many I.Cs. manufactured for this purpose A typical example of an I.C. boost converter is the LM27313 from Texas Instruments. This chip is designed for use in low power systems such as PDAs, cameras, mobile phones, and GPS devices. Another common adjustable boost converter is LM2577

Step 13: Integrated Circuits


An integrated circuit (IC), sometimes called a chip or microchip, is a semiconductor wafer on which thousands or millions of tiny resistors, capacitors, and transistors are fabricated. Integrated circuits (ICs) are a keystone of modern electronics. They are the heart and brains of most circuits. An IC can function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor. A particular IC is categorized as either linear (analog) or digital, depending on its intended application.
Linear ICs have continuously variable output (theoretically capable of attaining an infinite number of states) that depends on the input signal level. As the term implies, the output signal level is a linear function of the input signal level. Ideally, when the instantaneous output is graphed against the instantaneous input, the plot appears as a straight line. Linear ICs are used as audio-frequency (AF) and radio-frequency (RF) amplifiers. The operational amplifier(op amp) is a common device in these applications.
Digital ICs operate at only a few defined levels or states, rather than over a continuous range of signal amplitudes. These devices are used in computers, computer networks, modems, and frequency counters. The fundamental building blocks of digital ICs 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).
Depending on the way they are manufactured, integrated circuits can be divided into two groups: hybrid and monolithic. Hybrid circuits have been around longer.
IC Packages

The package is what encapsulates the integrated circuit die and splays it out into a device we can more easily connect to. Each outer connection on the die is connected via a tiny piece of gold wire to a pad or pin on the package. Pins are the silver, extruding terminals on an IC, which go on to connect to other parts of a circuit. These are of utmost importance to us, because they’re what will go on to connect to the rest of the components and wires in a circuit.
There are many different types of packages, each of which has unique dimensions, mounting-types, and/or pin-counts.
Pin Numbering

All ICs are polarized,and every pin is unique in terms of both location and function. This means the package has to have some way to convey which pin is which. Most ICs will use either a notch or a dot to indicate which pin is the first pin. (Sometimes both, sometimes one or the other.)
Mounting Style

One of the main distinguishing package type characteristics is the way they mount to a circuit board. All packages fall into one of two mounting types: through-hole (PTH) or surface-mount (SMD or SMT). Through-hole packages are generally bigger, and much easier to work with. They’re designed to be stuck through one side of a board and soldered to the other side.
Surface-mount packages range in size from small to minuscule. They are all designed to sit on one side of a circuit board and be soldered to the surface.
Common ICs
Logic Gates (7400 series), Timers (555, 556), Shift Registers (74HC164, 74HC595), Microcontrollers (PIC16F877A, ATmega328P), Microprocessors (8086, 80386, MC68030), FPGAs, Sensors(LM35, 5843), RTC (DS3231, DS1307), Etc.


mplete Guide for Tech Beginners (part-2) 

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