Chapter 15 : Familarize with IC

 

 

 

integrated circuit (IC), also called microelectronic circuit, microchip, or chip, an assembly

of electronic components, fabricated as a single unit, in which active devices (e.g., transistors and diodes) and passive devices (e.g., capacitors and resistors) and their interconnections are built up.

An IC can function as an amplifier, oscillator, timer, counter, logic gate, computer memory, microcontroller or microprocessor. An IC is the fundamental building block of all modern electronic devices

 

 

 

There are two main types of integrated circuits: Digital ICs or

Analog ICs.

1)  Analog IC

In this type of ICs, the input and output both signals are continuous. The output signal level depends upon the input signal level and the output signal level is a linear function of input signal level. Linear ICs or analog ICs are most commonly used as audio frequency amplifier and radio frequency amplifier. Op amps, voltage regulators, comparators and timers are also well-known examples of linear ICs or analog ICs.

 

 

2)    Digital IC

 

The logic Gates, such as AND gate, OR gate, NAND gate, XOR gate, flip flops, counters; microprocessors are some well-known examples of digital ICs.

These ICs operate with binary data such as either 0 or 1. Normally in digital circuit, 0 indicates 0 V and one indicate +5 V. Digital ICs are commonly used in many electronics projects, and are often used in Ardino .

 

Note of Familarize with transistor

CHAPTER 14 : FAMILARIZE WITH TRANSISTOR

 

 

 

A transistor is a semiconductor device used to amplify or switch electrical signals and power. The transistor is one of the basic building blocks of modern electronics.

Transistors are also used for low-frequency, high-power applications, such as power-supply inverters that convert alternating current into direct current. Additionally, transistors are used in high-frequency applications, such as the oscillator circuits used to generate radio signals.

How transistors work

A transistor can act as a switch or gate for electronic signals, opening and closing an electronic gate many times per second. It ensures the circuit is on if the current is flowing and switched off if it isn't. Transistors are used in complex switching circuits that comprise all modern telecommunications systems. Circuits also offer very high switching speeds, such as hundreds of gigahertz or more than 100 billion on-and-off cycles per second.

 

Transistors can be combined to form a logic gate, which compares multiple input currents to provide a different output.

Computers with logic gates can make simple decisions using Boolean algebra. These techniques are the foundation of modern-day computing and computer programs.

 

 

 

         TYPES OF TRANSISTOR

 

 

 

 

 

1)  NPN Transistor (Negative Positive Negative Transistor.):

NPN is one of the two types of Bipolar Junction Transistors (BJT). The NPN transistor consists of two n-type semiconductor materials and they are separated by a thin layer of p-type semiconductor. Here, the majority charge carriers are electrons while holes are the minority charge carriers. The flow of electrons from emitter to collector is controlled by the current flow in the base terminal.

A small amount of current at base terminal causes a large amount current to flow from emitter to collector. Nowadays, the more commonly used bipolar transistor is NPN transistor, because the mobility of electrons is greater than mo

 

 

2) PNP Transistor(Positive Negative Positive Transistor.)

The PNP is another type of Bipolar Junction Transistors (BJT). The PNP transistors contain two p-type semiconductor materials and are separated by a thin layer of n-type semiconductor. The majority charge carriers in the PNP transistors are holes while electrons are minority charge carriers. The arrow in the emitter terminal of transistor indicates the flow of conventional current. In PNP transistor, the current flows from Emitter to Collector.

 

 

Prepared By :Mausham Aryal(GSS 2079)

 

CHAPTER -13 :APPLY THE PRINCIPAL OF SEMICONDUTOR

 

A substance that can conduct electricity is called

the conductor and a substance that cannot conduct electricity is known as the insulator. Semiconductors have properties that sit between the conductor and insulator. A diode, integrated circuit (IC) and transistor are all made from semiconductors.

 

Computer chips, both for CPU and memory, are composed of semiconductor materials

 

A semiconductor is a substance that has specific electrical properties that enable it to serve as a foundation for computers and other electronic devices. It is typically a solid chemical element or compound that conducts electricity under certain conditions but not others. This makes it an ideal medium to control electrical current and everyday electrical appliances.

 

 

 

 

Uses of Semiconductors in Everyday life

·         Temperature sensors are made with semiconductor devices.

·         They are used in 3D printing machines

·         Used in microchips and self-driving cars

·         Used in calculators, solar plates, computers and other electronic devices.

 

TYPES OF SEMICONDUCTOR

 

1)   Intrinsic semiconductor:

An intrinsic type of semiconductor material is made to be very pure chemically. It is made up of only a single type of element.

Germanium (Ge) and Silicon (Si) are the most common type of intrinsic semiconductor elements. They have four valence electrons (tetravalent). They are bound to the atom by covalent bond at absolute zero temperature.

When the temperature rises, due to collisions, few electrons are unbounded and become free to move through the lattice, thus creating an absence in its original position (hole). These free electrons and holes contribute to the conduction of electricity in the semiconductor. The negative and positive charge carriers are equal in number.

2)  Extrinsic Semiconductor

The conductivity of semiconductors can be greatly improved by introducing a small number of suitable replacement atoms called IMPURITIES. The process of adding impurity atoms to the pure semiconductor is called DOPING. Usually, only 1 atom in 107 is replaced by a dopant atom in the doped semiconductor.

An extrinsic semiconductor can be further classified into:

 

·         N-type Semiconductor

·         P-type Semiconductor

 

 

 

 

N-Type Semiconductor

·         Mainly due to electrons

·         Entirely neutral

·         I = Ih and nh >> ne

·         Majority – Electrons and Minority – Holes

When a pure semiconductor (Silicon or Germanium) is doped by pentavalent impurity (P, As, Sb, Bi) then, four electrons out of five valence electrons bonds with the four electrons of Ge or Si.

The fifth electron of the dopant is set free. Thus, the impurity atom donates a free electron for conduction in the lattice and is called “Donar“.

Since the number of free electron increases by the addition of an impurity, the negative charge carriers increase. Hence, it is called n-type semiconductor.

 

P-Type Semiconductor

·         Mainly due to holes

·         Entirely neutral

·         I = Ih and nh >> ne

·         Majority – Holes and Minority – Electrons

When a pure semiconductor is doped with a trivalent impurity (B, Al, In, Ga ) then, the three valence electrons of the impurity bonds with three of the four valence electrons of the semiconductor.

This leaves an absence of electron (hole) in the impurity. These impurity atoms which are ready to accept bonded electrons are called “Acceptors“.

With the increase in the number of impurities, holes (the positive charge carriers) are increased. Hence, it is called p-type semiconductor.

 

 

 

DIODE SEMICONDUTOR

A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other.

The diode have two points, one anode and anathoer cathode.

DIODE ARE ONE DIRECTIONAL(Positive to Negative ).

Diode are used in turning AC to DC , Inverters, Powe r supply etc

 

 

 

 

Working principle of semiconductor diode

N-type have a significant number of free electrons and very few holes. But in P-type, It has a high concentration of holes and very few free electrons. For this reason, the free electron from n side will diffuse into the p side and recombine with holes present there, leaving position is not movable ions in n side and creating negative immobile ions in the p-type side of the diode.

Hence, revealed positive giver particles present in the n-type side close to the junction edge. Correspondingly, revealed negative acceptor particles present in the p-type side close to the junction edge.

For this reason, the number of positive ions and negative ions will accumulate on n-side and p side too. This region is formed in the depletion region due to the free carrier in the region.

 

 

Because of the nearness of these positive and negative ions, a static electric field called as barrier potential is made over the PN junction of the diode. It is classified “barrier potential” since it goes about as an obstruction and opposes the further migration of gaps and free electrons over the junction.

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TYPES OF DIODES

 

 

 

Light Emitting Diode (LED)

When an electric current between the electrodes passes through this diode, light is produced. In other words, light is generated when a sufficient amount of forwarding current passes through it. In many diodes, this light generated is not visible as there are frequency levels that do not allow visibility. LEDs are available in different colours. There are tricolour LEDs that can emit three colours at a time. Light colour depends on the energy gap of the semiconductor used.

Laser Diode

It is a different type of diode as it produces coherent light. It is highly used in CD drives, DVDs and laser devices. These are costly when compared to LEDs and are cheaper when compared to other laser generators. Limited life is the only drawback of these diodes.

Avalanche Diode

This diode belongs to a reverse bias type and operates using the avalanche effect. When voltage drop is constant and is independent of current,

the breakdown of avalanche takes place. They exhibit high levels of sensitivity and hence are used for photo detection.

Zener Diode

It is the most useful type of diode as it can provide a stable reference voltage. These are operated in reverse bias and break down on the arrival of a certain voltage. If current passing through the resistor is limited, a stable voltage is generated. Zener diodes are widely used in power supplies to provide a reference voltage.

Zener diodes are used for voltage regulation, as reference elements, surge suppressors, and in switching applications and clipper circuits

 

 

 

Prepared By :Mausham Aryal (GSS 2079)