DEV Community: Emma Ashely

PCB: Definition, Types, Material, Manufacturing Process, Price & Applications

Emma Ashely — Mon, 30 Aug 2021 09:46:37 +0000

Hi Guys! Hope you’re well. Happy to see you around. In this post today, I’ll walk you through PCB (Printed Circuit Board) in detail.

PCBs are commonly used in simple electrical circuits and advanced electronic devices. They ensure compact and concise designs where electronic components are placed for the electrical connection in a secure fit. PCB designs have evolved and changed in so many ways since their inception. You cannot compare the heavy PCBs installed in old TVs with the sophisticated and lightweight boards used in supercomputers and nano boards used in the development of pacemakers. Earlier end-to-end wiring was used that was costly and would cover more space. PCBs not only removed the need for this erratic wiring but with the more advanced technology they went through significant development. Now you can produce different types of boards including rigid PCB, flexible PCB, rigid-flex PCB, aluminum-backed PCB, high-frequency PCB, and more. PCB Panelization is a normal practice, used for design products and handheld devices in bulk.

I suggest you read this post all the way through as I’ll be covering each and everything related to PCB including definition, types, material, manufacturing process, price & applications.
Let’s jump right in.

Definition:

PCB (Printed Circuit Board) is a board that provides mechanical support and electrical connection to the electronic components placed on the board. The board comes with conductive copper traces that are laminated on the non-conductive substrate.

Types:

PCBs are categorized into three different types based on the number of conductive layers used to manufacture the board.

Single-Sided PCB Boards

Single-sided boards, also known as single-layer boards, are PCBs that contain conductive copper tracks on one side of the board. In these boards, the electronic components are inserted from one side (non-conductive substrate) to the other side that contains copper tracks. The electrical connection is established when components pins are soldered with conductive copper tracks.

Double-Sided PCB Boards

Double-sided boards, also known as the double-layer board, are PCBs that contain conductive copper tracks on both sides of the board. Two techniques are used to mount electronic components on these boards: Surface mount technology and Through Hole. Know that these boards come with a single layer of base substrate but conductive copper tracks are added on both sides of the substrate.

Multilayer PCB Boards

Multilayer PCB boards contain multiple double-layered PCBs. These boards are then combined with glue by inserting the pieces of insulation between them to prevent the boards from the excessive heat that can hurt the boards. The number of double-layered PCBs in Multilayer boards varies from 4 layers to 16 layers or more. These boards are more complex in composition than the standard PCBs and are employed in applications like weather equipment, satellite equipment, data storage, GPS technology, and x-ray equipment.

Material:

The six components of the PCB include:

Prepreg
Laminate
Copper foil
Solder mask
Nomenclature
Final finish

Prepreg is a substrate material made up of fiberglass and is plated with resin. Know that the most common resin that we use as a substrate is FR4. Laminates, also known as copper-clad laminates, are composed of substrate sheets laminated together with heat and pressure. Next, copper foil is coated on the board that serves as a conductive path for the electrical components we mount on the board.

The solder mask sits on the copper foil. This solder mask layer is used to provide insulation to the copper layer. Nomenclature, also known as silkscreen, is the ink-jet writing on the top of the solder mask, indicating critical board information. To guard the exposed copper holes and to ensure a smooth solderable finish, a metallic coating of nickel, gold, or silver is commonly used.

Manufacturing Process:

PCBs are made up of conductive copper laminated on the non-conductive substrate material. PCB comes with multiple layers that are glued together to ensure a compact structure.
The printed circuit board’s manufacturing process includes the following steps.

Designing the PCB

To start the PCB manufacturing process, first, you need to have the PCB design. In this step, the designer makes the blueprint for the PCB based on the requirements. The computer software is normally used to make the PCB design. Commonly used PCB design software include Protell (Altium Designer), OrCAD, PADS, Eagle, EasyEda, and Extended Gerber.

Printing the Design

Know that PCB designs are not printed out on the traditional 8.5x11 sheet as we use for architectural designs. Instead, a Plotted printer, a special kind of printer, is used to print out the PCBs. This printer produces PCB film which is nothing but a transparent negative of the board showing details and layers of the board.
The PCB inside layers come with two ink colors:

Black Ink: that exhibits the conductive copper traces and PCB circuits
Clear Ink: that exhibits the non-conductive PCB areas The inner layers follow this trend but for the outer layers, this trend is reversed i.e. blank ink shows the non-conductive PCB areas and clear ink shows the conductive copper traces. ### Printing the Inner Layers

The design is printed out onto a laminate which is the basic structure of the board. Next, the resist covers the laminate panel; the resist is a photosensitive film composed of photo-reactive chemicals that turn to hard material when exposed to UV light. The resist helps align the PCB blueprints with the actual PCB print. To make sure the laminate and resist are perfectly aligned, holes are then drilled onto the board.

Exposure to UV light

Once resist and laminate lined up, they receive the storm of UV light that hardens the photoresist. The UV light reveals the copper pathways while black ink, on the other hand, stops the light from entering the areas that are not supposed to get hardened, helping you remove those less hardened areas later. Once prepared, the board is then washed out with an alkaline solution to get rid of excessive photoresist.

Removing the unwanted Copper

In this step, we’ll remove the unwanted copper that remains on the board. A more powerful solution, similar to an alkaline solution, is then used to remove the excessive copper, leaving the required copper fully intact under the layer of photo resist.

Inspection

An inspection is required for the new washed-out layers. The holes drilled earlier help to line up the outer and inner layers. The layers are further passed through the optical punch machine that drills a pin through the holes to make sure layers are lined up. Another machine is then employed to ensure the board carries no defects.

Laminating the Layers

In this step, the board starts taking the shape as the layers are fused together. Metal clamps are used to clutch the layers together as the laminating process starts. A Prepreg (composed of sheets of fiberglass with epoxy resin) is then placed over the alignment basin. The substrate layer sits over the Prepreg before you place the copper sheet. More sheets of Prepreg material are then placed on top of the copper layer. The composition is ready to go through the mechanical press.

Pressing the Layers

A mechanical press is then employed to fuse the layers together. To keep layers properly aligned and secured, pins are punched through the layers; pins can be removed later. The board then goes through the laminating press that applies the pressure and heat to the layers. The applied pressure and the melted epoxy inside the Prepreg then help in fusing the layers together.

Drilling & Plating

A computer-guided drill is then used to drill the holes into the layers that expose the inner panels and substrate. After this step, any leftover remaining copper is removed before the circuit board is ready to get plated. A chemical solution is used to fuse the layers together. The structure is then completely washed out by a series of chemicals. These chemicals then deposit a thin layer of copper on the panel surface. The thin copper layer crawls into the recently drilled holes.

Outer Layer Imaging

In this step, we apply a layer of photoresist onto the panel, as we did in step 3. The panel then undergoes a blast of UV light that makes the photoresist hard. The unwanted and unhardened resist is then removed by the machine.
Plating
In this step, the thin copper layer is coated over the panel, as we did in step 9. After the copper plating, a thin layer of tin is applied on the board that protects the panel section that is supposed to remain covered with copper layer during the following etching stage.

Final Etching

The PCB’s connections are established in this step. The same chemical solution applied before is used to remove the undesired copper beneath the resist layer.

Solder mask application & Silkscreening

The entire composition is thoroughly cleaned and covered with an epoxy solder mask ink before applying the solder mask. The board then comes under the blast of UV light that removes the unwanted solder mask and the board is then baked in the oven to keep the desired solder mask. Silk screening is applied before the last coating and curing stage. Silk screening applies ink-jet writing on the board’s surface, indicating critical information of the board.

Surface Finish

Based on the requirements, the final composition is plated with a solderable finish, increasing the quality of the final structure.

Testing

An automated Electrical test is performed on the board to ensure the functionality of the board and its resonance with the initial design.

Price:

PCB pricing is mainly dependent on three major factors including the board size, type of the material, and the number of layers. Obviously, the cost of the thicker board with a large size is significantly higher than the cost of the thin board with a small size. Similarly, the multiplayer board is costly compared to a standard single layer and double layer boards.
Other factors that affect the cost of the circuit board include:
Size of hole

Minimum trace and space

The thickness of the PCB and Aspect Ratio
Custom and Unique Specs The custom specs may vary depending on the application. Like the circuit boards that come with rounded edges would require more cost to manufacture, especially those that need z-axes routing. Similarly, if you require metal edges, the price of the board will go high. If extra thickness and clearance are required of the solder mask, it will cost more.

Applications:

The applications of PCBs include:

PCBs are commonly used for industrial and commercial purposes like in dashboards, power supplies, fuel regulators, heat control systems, satellite navigation, and more. Moreover, they are also a part of many electronic circuits used to join the electronic components together.
LED-based lighting systems consume lights 90% less than traditional light bulbs and they come with Aluminum backed PCBs, ensuring high efficiency and low power consumption. The main purpose of these boards is to offer economical, compact, and the smallest designs possible; the reason they are the right match for medical equipment like pacemakers, CAT scanners, and x-ray machines.
Flexible circuit boards are commonly used in the aerospace and automotive industries. The flexibility feature of these boards can endure extreme vibrations, preventing the instruments from accidental damage. Moreover, due to their lightweight, they are widely used in transportation industries for the development of manufacturing parts. That’s all for today. Hope you’ve enjoyed reading this article. If you have any questions, you can approach me in the section below. I’d love to help you in the best way possible. Thank you for reading this post.

Flexible PCB: Definition, Types, Material & Manufacturing Process

Emma Ashely — Wed, 18 Aug 2021 04:33:06 +0000

Hi Friends! I welcome you on board. Happy to see you around. In this post today, I’ll walk you through Flexible PCB in detail.
Flexible circuit boards are commonly used in laptop computers, cell phones, and digital cameras. These boards can fit in hard-to-reach places due to their lightweight and compact structure. They range from single-layer boards used in simple electronic units to multilayer complex boards used in advanced electronic applications. You can twist, fold and even flex these boards into a rolled-up configuration. Flexible boards exhibit three-dimensional packaging geometry and offer wiring solutions to the electronic applications where rigid boards fail to meet the requirements. They cover less space as they come with the thinnest substrate material as thin as 0.0004 inches. The inception of flex boards has replaced many types of wiring done by hand, reducing the overall price of electrical wiring by up to 70%.
I suggest you read this post all the way through as I’ll cover each and everything related to Flexible PCB including definition, types, material, manufacturing process, price & applications.
Let’s get started.

Definition

A flexible PCB is a special type of circuit board that you can twist, fold and bend into any desired shape. In the flex boards, the polyimide substrate material is used that comes with remarkable heat resistance, making it a right fit for solder mounting components. They work perfectly in extreme environments and can withstand shocks and vibrations due to their flexible nature.

Types of Flexible PCB

The types of flexible circuit boards include:

Single-Sided Flexible PCB

The single-layer Flexible PCB, also known as single-sided PCB, carries only one conductive copper layer. The conductive layers sit on the flexible dielectric film. Electrical components can be added on only one side of the board.

Double-Sided Flexible PCB

Conductive copper layers are added on both sides of the board in a double-sided flexible PCB, increasing the wiring density per unit area. Electrical components can be attached on either side of the copper layer.

Multiple Layer Flexible PCB

The multi-layer flexible PCB carries three or more conductive copper layers. These layers are separated by a dielectric material. Multilayer units exhibit higher reliability, better thermal conductivity, and offer easy assembly. Polyimide substrate material is used for flexible boards that is 1/3 lighter than the substrate material used in rigid boards.

Rigid-Flex PCB

The rigid-flex designs have the ability of both flexible and rigid circuit boards. These boards come with higher component density compared to other traditional circuit boards.

HDI Flexible PCB

The HDI (high-density interconnect) circuit boards are the type of flexible boards that guarantee reduce package size and exhibit remarkable electrical performance. The thin substrate material is used for the production of HDI flexible boards, ensuring seamless layout design and better construction.
Material
You can pick from three types of substrate materials available for the manufacturing of flex boards. First is polyester that is mainly employed in low-end products, next is polyimide (PI) that is commonly preferred in flex boards and is more expensive than fiberglass or FR-4 substrate material used in rigid circuit boards. Third is fluoropolymer that is widely used in military and aerospace products.
When you compare these three susbtrate material mentioned above, you’ll notice the PI film exhibits highest dielectric constant and shows remarkable electrical properties and resistance towards high temperature, which means PI film stays flexible and doesn’t soften when heated at a high temperature.
Standard PI films don’t exhibit good resistance to tears and humidity, however, picking the quality and upgraded PI films can remove such issues. An adhesive or special base material is used in flex circuits for its layers to attach.
Solder mask is not used in flex boards, instead, coverlay film created with PI is used to protect flex circuits. If the rigid portion is required on the flex circuit, stiffer is laminated on that area that offers stiffness and strength to the board. Know that no signal path is laid out between the stiffer and the board.

Manufacturing Process

The manufacturing process of flex circuit boards is slightly different than the process used to manufacture rigid boards. The following figure shows the three major steps involved in the manufacturing of flexible PCBs.

Step 1: Flex PCB Build Up

The base material used for flex boards is polyimide which is costly than the FR-4 material used in rigid boards. So it is wise to use base material carefully, especially if you want to manufacture the circuit boards with lower costs. More often, the nesting technique is used to save polyimide where circuits are placed adjacent to each other. Normally the circuits come with four segments per panel, however, you can make it 16 segments per panel if you employ the nesting technique.
The manufacturing process of the flex circuit boards include:

Service Loop

The service loop is adding a slight amount of extra material more than the designer’s limit to the circuit board. Use service looping if you want to improve the assembly or servicing length of the circuit.

Selecting Copper

It is preferred to pick the thinnest copper to apply remarkable flexibility to the circuit. The thinnest copper comes in handy especially when you intend to use the circuit board for dynamic applications.

Etching

The manufacturing process may lead to isotropic losses. The etching process is used to compensate for those losses. In this process, the copper foil thickness is almost half the line width loss. Line width can be influenced by different factors including different types of copper, equipment, conductor, and etch mask.

Routing

Conductor routing is applied to the specific regions of the circuits to reduce stress and to improve the bending and folding capability of the circuit board.

Ground Planes

Ground planes are created to reduce the overall weight of the circuit board and to improve circuit flexibility.

Step 2: Flexible Circuit Board Fabrication Process

In this step, we’ll further expand on the process that occurred on the circuit boards. First, we’ll discuss conductor spacing and width.
When you’re using polymer thick films then the common conductor width would require 375 micrometers. Nominal polymer thick films come with the ability to carry current. While silver-based thick films, on the other hand, can support 25% of the total circuit current.
In flex boards, the diameters for through holes can vary from 200 to 250 micrometers based on the design and the application.

Hole Size

Manufacturers can create small holes based on the design. With the inception of advanced technology, manufacturers can produce holes as small as 25 micrometers.

Filleting

Filleting is applied on the pads and land termination points to evenly distribute the stress. Plated through-holes are used to create an efficient solder joint.

Button Plating

This method is used to create a substitute plated through-hole where copper is used to creating vias and through-holes.

Step 3: Consider Physical Constraints and Possible Chemical

In this section, we’ll discuss cover layers and cover coating issues. The coverlays are used in flex boards instead of solder mask that is used in rigid boards.
The common cover layers employed in the manufacturing process include:

Adhesive Backed Films

Adhesive-backed films come with balance raw materials, making them a suitable match for dynamic flex circuit applications. The majority of manufacturers use these films for cover coating.
Screen-printable liquid overcoats
It is preferred to use screen-printable liquid overcoats to save cost.

Photo imaginable liquid and film polymers

This method is commonly used for over-coating as it doesn’t show any irregularities as you happen to deal with other cover layers.

The crucial features of this cover layer include:

This cover layer secures the circuit board from external and internal damages.
The layer behaves as a solder mask, preventing the solder from circuiting tracks.
Keeps the circuit board from external electrification.

These are three major steps to manufacture flexible circuit boards. However, they may vary from manufacturer to manufacturer.
Price
Flex circuit boards simplify component assembly and can reduce erratic wiring. They are lightweight and can fit into less space. The cost may vary for different boards based on the three different factors:
Physical size: The physical size of the board does affect the overall cost of the board. The more the size, the more the cost. The flex boards are normally manufactured in rectangular panels. The cost mainly depends on the number of boards you can nest in a panel. The more boards you can incorporate on the panel, the less price you’ll pay per circuit.
Circuit Construction: The number of conductive layers per circuit also defines the cost of the board. The multilayer board would cost more than the standard single-layer flexible board.
Volume: The more the quantity, the lesser the price of the board.
Other important factors that can influence the price of the board include :

Minimum trace and space
The thickness of the PCB and Aspect Ratio
Size of hole
Custom and Unique Specs The custom specs depend on the application. Like the boards that include rounded edges would need more cost to manufacture. Similarly, if you demand metal edges for your board, the price of the board will increase.

Applications

The need for flexible circuits is increasing, with applications in the simple and advanced electronics sectors including automotive, consumer, electro-medical devices, telecommunications, wearables, and aerospace.
The common flexible PCB applications include:

Used in dynamic flexing application in which flex boards can be bent several times.
Used in laptop computers, cell phones, and digital cameras.
Employed in the medical field like the production of hearing aids, pacemakers, and heart monitors.
Widely incorporated in processing machines, robotic arms, and bar code equipment.
Lightweight and an ability to cover less space make these boards a suitable fit for satellite and GPS applications. That’s all for today. Hope you’ve enjoyed reading this article. You can pop your comment in the section below if you’re unsure about anything. I’ll help you out the best way I can. Thank you for reading this article.

Enhancement Type MOSFET

Emma Ashely — Mon, 02 Aug 2021 00:54:08 +0000

Hello friends, I hope you are fine. Today, we will discuss the Enhancement Type Mosfet. As we are done with the basic understanding of the regions under which the IV characteristic curve operate, we would now discuss the characteristics of MOSFET specific to their different subtypes. So, let's get started with this type of transistor:

I-V characteristics of N channel enhancement type MOSFET

The characteristics curve for N channel enhancement MOSFET is drawn for the varying values of drain to source current IDS with the voltage VGS which is the gate to source voltage.
The current would be zero because of the absence of a conduction channel between the source and drain until the VGS which is the gate to source voltage reaches the threshold voltage represented by VT.
Refer to the following graph for better understanding:

Under such circumstances what you think the increase in the drain to source voltage would do? Let me make this clear for you, there wouldn't be any increase in the IDS which is the drain to source current, have you thought why? Because the conduction channel is still not there, so there is no point of increasing the current without the conduction channel, you can’t make a banana smoothie without bananas! This phenomenon represents the cut-off region of the graph. We can mathematically write it as: VGS < VT
In the next step, the Gate to source voltage VGS increases in value increasing the Current IDS, this is represented by the Ohmic region of the V-I characteristic curve. The mathematical expression can be written as: VGS > VT and VDS < VP
Later on, VGS crosses the threshold voltage VT, keeping the current IDS constant and is represented as the saturated region of the graph. For this region we can write it as: VGS > VT and VDS > VP
The gate to source voltage VGS keeps on increasing the current IDS even in the saturated region until a defined value of voltage is reached known as Pinch off voltage, you can check this in the saturated region of our graph.
You can yourself guess the majority of charge carriers involved in the conduction process, can’t you?

I-V characteristics of P channel enhancement type MOSFET

The transfer characteristics of P channel enhancement type MOSFET are plotted between the varying values of Drain to Source current IDS with the gate to source voltage VGS.
Refer to the following graph for better understanding:

The IDS, drain to source voltage remains zero in the cut-off region because the conduction channel is not established until the gate to source voltage crosses the threshold voltage VT. can Mathematically write it as: VGS > -VT
After crossing the threshold voltage VT the VGS causes an increase in the Drain to source current in the reverse direction, represented by ISD because the conduction channel has been established by now. The region representing this state of affairs is labeled as the Ohmic region on the graph, you can follow the graph step by step for better understanding. For this region we can write the mathematical expression as: VGS < -VT and VDS > -VP
In the next phase, the VDS which is the drain to source voltage reaches the pinch-off voltage VP, at this stage saturated current flows through the P channel enhancement type MOSFET which is represented by the saturated or active region of the graph. We can summarize the whole scenario by writing it as : VGS < -VT and VDS < -VP
As the negative value of Voltage VGS increases the drain to source current represented by IDS increases. You can easily point it out from the graph! Scroll up and correlate the values of VGS with IDS, aren't they increasing with the increasing negative value of the voltage?

Depletion Type MOSFET

Emma Ashely — Sun, 01 Aug 2021 23:47:46 +0000

We will talk about the working of depletion MOSFETs now in general .Here are a few important features to remember which would help you out later on,
They are commonly known as Switched On devices.
In depletion mode, the width of the channel is dependent on the gate voltage.
If the applied gate voltage is positive then the channel width would eventually increase, as we discussed earlier.
On the other hand, if a negative voltage is applied to the gate, the width of the channel decreases, and hence the drain Current ID also decreases.
If the negative voltage is much higher in value, then the MOSFET shifts into the cut-off region.
MOSFET characteristics vaires from a normal FET, short for field effect transistor.

I-V characteristics of Depletion mode MOSFET

Here is a brief overview that how is it done, we will discuss both the types later in this section;

The V-I characteristics of depletion-mode MOSFET are plotted between the varying values drain-source voltage represented by VDS, with the Drain current ID.
Initially, a little amount of gate voltage produces a small drain current represented in the Ohmic region of the graph.
As the value of positive voltage increases, the value of drain current also increases and reaches the maximal potential of the MOSFET, this region is labeled as Saturated or Active Region.
In the case of applying a negative voltage to the gate, we would get a sharp decline in the value of Drain Current ID as you can see from the graph.

I-V characteristics of N channel depletion type MOSFET

Let us discuss the current transfer characteristics of the N channel depletion types MOSFET with the help of a characteristic curve plotted between the drain to source voltage VDS and drain to source current represented by IDS.
Refer to the graph given below for better understanding:

You can observe from the graph that a little amount of current is still flowing through the N channel depletion type MOSFET even when the VGS is zero. This is represented by the cut-off region of our graph. Mathematically we can summarize it as; VGS < -VT

In the next phase the current IDS starts increasing with the increasing value of VDS, this phenomenon can be observed in the Ohmic region of the graph. The mathematical expression can be written as: VGS > -VT and VDS < VP
After the Ohmic region, there is the saturated region of our graph, by now you must be aware of what is happening in this region? If not, let me solve it for you, N channel depletion type MOSFET operates in the saturated region when the VDS reaches a certain value of voltage called Pinch off voltage. Pinch-off voltage is represented by VP. After reaching the pinch-off voltage our n channel MOSFET passes the saturated current.
It is evident from the graph that, the value of VP and IDS would increase with the increasing value of VGS. We can summarize the whole scenario as ; VGS > -VT and VDS > VP
Here a question arises, what would you do if you want to operate your N channel depletion mode MOSFET in the cut-off state? The answer to this question is simple, make your VGS which the gate to source voltage negative, and voila you are done!
At the point at which the VGS reaches the negative voltage level of -VT, IDS would become Zero, no IDS means no channel leading to no conduction!

I-V characteristics of P channel depletion type MOSFET

P channel depletion type MOSFET has majority charge carriers in the form of holes, the characteristic curve is plotted between the VGS which is the Gate to source voltage, and current IDS, which is the drain to source current.
Refer to the graph given below for better understanding:

By default, we have the conduction channel already established to an extent in P channel depletion type MOSFET so the current IDS is not zero even when the voltage VDS is zero. This is represented in the cut-off region of our graph. In this case : VGS > VT
The value of current represented by IDS increase with the value of VDS, refer to the Ohmic region of our graph, refer to the graph for a better understanding. We can summarize that: VGS < VT and VDS > -VP
Afterward, when the VDS reaches a certain maximal pinch-off voltage VP, P channel depletion type MOSFET starts operating in the Saturated region. We can summarize the whole process by writing the following expression: VGS < VT and VDS < -VP
The saturated current increases with the negatively increasing value of VDS, Follow the values of IDSS, from IDSS1 to IDSS3 with the values of VGSO to the values of VGS3, can you figure out the pattern?
When VGS is equal or greater than the threshold voltage VT, then at this point, the P channel depletion type MOSFET would lose its conduction channel reaching the pinch-off voltage, this would, in turn, leave the P channel depletion type MOSFET again into the cut off region switching off the device.
So, this was the last segment for the characteristics of our MOSFET, let us move to the final notes to conclude this discussion.

What is BJT? Everything You Need to Know

Emma Ashely — Thu, 29 Jul 2021 18:27:27 +0000

Hi there! Glad to see you. Thank you for stopping by. In today’s post, I’ll be covering BJT (Bipolar Junction Transistor) in detail.

BJTs are commonly used in electronic circuits as an amplifier, oscillator, rectifier, filter, and even as a switch. BJTs are bipolar electronic devices that use both electrons and holes as charge carriers.

Curious to know more about BJTs?

Stay connected.

BJT Definition:

The BJT(bipolar junction transistor) is a three-terminal semiconductor electronic device mainly used for switching and amplification applications. The three terminals are named: emitter, base, and collector. In BJTs, the large current at the collector and emitter sides is controlled by the small input current at the base terminal. Earlier, germanium was used for the development of BJTs, while recent BJTs are composed of silicon material.

BJT Symbol:

The BJT is divided into two main types: NPN and PNP and symbols of both transistors are shown below.

The direction of the current flow in symbols is represented by the arrows. Current flow will occur from emitter to base side in PNP transistor and from base to emitter side in NPN transistor.

BJT Working:

The base pin is responsible for the working of the entire device. The voltage at the base pin will turn ON the NPN transistor and current flow will occur from the collector to the emitter pins. This current flow is denoted by Ic and is called collector current. In an NPN transistor, there are two junctions: one is a base-emitter junction that is forward-biased and the other is a collector-base junction that is reverse-biased.

The depletion region width at the base-emitter junction side is less than the depletion region width of the collector-base junction. The base-emitter junction is forward biased and the potential barrier is decreased at this junction which will cause the electron flow from the emitter to the base side.
The electrons at the base region are not held there for the maximum time since the base side is very thin and lightly doped. These electrons will make pairs with the holes available at the base side and as a result, they flow out of the base side in the form of base current. The leftover electrons that don’t get attached to the holes at the base region then enter the collector region as a collector current.
Based on Kirchoff’s Current Law, when we add both base current and collector current, they will be equal to emitter current.
Ie = Ib + Ic
This is how the NPN transistor works. The working of the PNP transistor is similar to the NPN transistor but holes are majority carriers in the PNP transistor and the current flow will occur from emitter to collector pins.

BJT Characteristics:

All there pins of the BJT device come with different doping concentrations. The base side is thin and lightly doped and the emitter side is highly doped while the collector terminal is moderately doped.

There are three different configurations to connect BJT devices:

Common-base configuration
Common-emitter configuration
Common-collector configuration

We’ll study each one by one.

A: Common-base configuration

In this configuration, the base pin is kept common between the input and output signals.

The characteristics of the BJT can be best explained by the V-I curve. In the following curve, we’ll take base-emitter voltage Vbe on the x-axis, and emitter current Ie is taken on the y-axis

The following figure shows the output curve of the common base configuration where collector-base voltage Vcb is taken on the x-axis and the collector current Ic is taken on the y-axis.

The characteristics curve exhibits three different regions called the cutoff region, saturation region, and active region. Both emitter and collector junctions are reverse biased in the cutoff region, and both emitter and collector junctions are forward biased in the saturation region and the emitter junction is reverse biased in the active region.

B: Common-emitter configuration

In this configuration, the emitter terminal is kept common between the input and output signals.

The following graph shows the input characteristics curve of the common-emitter configuration where base-emitter voltage Vbe is kept on the x-axis and the base current is taken on the y-axis.

The collector-emitter voltage Vce on the x-axis and the collector current on the y-axis shows the output characteristics curve of the common-emitter configuration which, similar to the common-base configuration, carries three regions. Both collector and emitter junctions are forward biased in the saturation region, while emitter junction is not fully reverse biased and collector current is not fully cut off in the cutoff region. And the collector junction is reverse biased and the emitter junction is forward biased in the active region.

C: Common-collector configuration

This configuration is also called voltage follower circuit where collector terminal is kept common between input and output signals.

In this configuration, the input impedance is high and is mainly used in impedance matching circuits.

BJT Types:

BJT are divided into two basic types:

NPN Transistor
PNP Transistor

Let’s study each one by one.

1: NPN Transistor

NPN transistor belongs to the BJT family where two N-doped layers surround the one P-doped layer. The base terminal is the middle P-layer while the other two N-layers show the collector and emitter pins. In NPN transistors, both electrons and holes take part in the conduction process, but holes are minor carriers in this case while electrons are the major carriers. The applied voltage at the base side will bias the device and as a result, the current flow will occur from the collector to the emitter pins.

2: PNP Transistor

PNP transistor belongs to the BJT family where two P-doped layers surround the one N-doped layer. The base pin is represented by the N-layer while collector and emitter pins are represented by two P-doped layers. Again, both electrons and holes take part in the conduction process in the PNP transistor, but electrons are the minor carriers and holes are the major carriers. The voltage at the base pin will bias the device and the current flow will occur from the emitter to collector pins.

Know that the mobility of electrons is better and faster than the mobility of holes, the reason NPN transistors stay ahead over PNP transistors for their usage in electrical circuits.

BJT Applications:

BJTs are commonly employed for amplification and switching purposes.
BJTs carry high voltage gain and low forward drop voltage; the reason they are the right match for voltage, current and audio amplification applications.

That’s all BJTs. Hope you’ve found this article useful. You can approach me in the section below if you’re unclear about anything. I’ll try my best to help you out. Thank you for your precious time.

Diode and their characteristics.

Emma Ashely — Thu, 15 Jul 2021 08:28:33 +0000

Hi there! Glad to see you. In this post today, I’ll walk you through Diode in detail.
Read the entire post as I’ll discuss each and everything related to Diode such as Diode definition, characteristics, working, symbol, types, and applications.
Let’s get started.

Definition:

A diode is a device in which current flows in one direction only. It is a one-way electronic valve that comes with two terminals named anode and cathode. The anode pin is a positive terminal and the cathode pin is a negative terminal and the device allows the current to flow from the anode pin to the cathode pin and it shows maximum resistance for the current to flow in the opposite direction.

Symbol:

The electrical symbol of the diode is shown below.

Diode Working:

The diode device carries two junctions: the N junction and the P junction. And the working of the diode is mainly dependent on the interaction between these two junctions. The N junction is an area that comes with a high concentration of electrons and the P junction is an area that comes with a high concentration of holes.
The diode working can be explained using the following three conditions.

Forward Biased Diode:

In this forward biased condition, the N side of the diode is connected with the negative source terminal and the P side is connected with the positive source terminal as shown in the figure below.

There will be no current flow in the diode when we increase the source voltage from zero. The zero current is due to the availability of the potential barrier. But when we increase the applied voltage above the forward potential barrier the diode will start acting as a short-circuited path and the current resistance occurs due to the external resistors.

Reverse Biased Diode:

This condition is opposite to the forward biased condition. In this condition the diode is connected with the power supply in reverse order i.e. the N side is attached with the source positive terminal and the P side is connected with the source negative terminal.

In the reverse biased condition, there is an electrostatic attraction in the depletion region that allows the holes in the P region to move away from the depletion region, leaving more uncovered negative ions. Know that, in this case, the current flow through the circuit is zero.

Unbiased PN-Junction Diode:

Unlike the two conditions mentioned above, there is no voltage applied from the external source in the unbiased PN junction. However, when you combine both N and P junctions, it allows the electrons to flow from the N material to the P material, and consequently, the holes will flow from the P side to the N side.

This flow of electrons and holes will produce the third region called the depletion region where no charge carriers are involved.

Diode Characteristics:

The current-voltage curve is used to define the characteristics of the diodes. We take voltage on the x-axis and current on the y-axis and will measure the respective voltage for a certain amount of current. The V-I relation is linear in the case of resistors but for diodes it is different. The diode V-I curve is shown in the below figure. The diode works in three regions according to the voltage applied across it. Forward Bias Region: When the voltage across the diode is positive, the current starts flowing through it, and the device will be turned ON. This is the forward bias region, and for the current to flow in this region, the positive voltage must higher than the forward voltage Vf.
Reverse Bias Region: In the reverse bias region the forward voltage Vf is more than the applied voltage while the applied voltage is more than the breakdown voltage and the device will be turned OFF. In this scenario, the current flow is minimum as the device shows the maximum resistance but a small current flow will occur in this condition, called reverse saturation current. Breakdown Region: In the breakdown region the flow of current is in the reverse direction (from cathode terminal to anode terminal) when the very high negative voltage is applied to the device. ##Types of Diode: The different types of diode include:
Photodiodes: Photodiodes are light sensitive and are widely used in optical communication and solar cell applications. They come in a material where light can easily pass through them. Multiple diodes can be packaged in a single device to form a linear or two-dimensional array.
Zener Diodes: Normally, the diode conducts in forward biased condition, however, in the case of the Zener diode, the scenario is different. Zener diode conducts in reverse bias conditions. The breakdown voltage of the Zener diode is less than 5V and they are generally called reverse breakdown diodes. The Zener diode is a heavily doped semiconductor device that forms a thin deletion region that results in increasing the electric field intensity.
Crystal Diodes: Crystal diodes are also known as point contact diodes where anode pin is comprised of thin metal and cathode pin is made up of semiconductor crystal material. These diodes are not so common and are also known as Cat’s Whisker diodes.
PIN Diodes: PIN diodes are used as frequency switches and attenuators and they carry an un-doped central layer due to the p-type/intrinsic/n-type structure. These diodes can endure high voltages and are a right match for power electronics applications.
Avalanche Diodes: Avalanche diodes are identical to Zener diodes, however, there is one difference i.e. both diodes contain temperature coefficients of different polarities. The current starts flowing in these diodes in the reverse direction when the reverse-biased voltage exceeds the breakdown voltage.
LED Diodes: LED diodes, also called low-efficiency diodes, are electric devices that are capable of emitting light of different colors like red, orange, blue, and green. The color of the emitted light depends on the crystalline substance used in the device. These diodes are mainly employed in signal applications due to their light-emitting capability.

Diode Applications:

The applications of the diodes include:

Incorporated to control the current flow
Used for temperature measuring applications
Used for demodulation of the amplitude signal
Employed as a waveform clipper
Employed in the making of rectifiers for converting AC signal to DC signal That’s all about the diode. Hope you’ve enjoyed reading this article. If you have any queries, you can approach me in the section below where I’ll answer your questions the best way I can. Thank you for your precious time.

Top Embedded Projects in IoT Technology

Emma Ashely — Sun, 11 Jul 2021 10:38:00 +0000

Hi Guys! I welcome you on board. Happy to see you around. In this post today, I’ll walk you through Top Embedded Projects in IoT Technology.
You may get skeptical while you listen to the term Internet of Things or IoT. Don’t be. It is not a new term anymore. IoT is on the rise, and if it continues to expand with the recent pace, that day is not far when a human being is considered as the thing on the internet. Experts say… almost 24 billion devices will be connected as IoT devices by 2050 and the global IoT market is expected to be worth $1.5 trillion by 2030.
In this post, we’ll discuss the Top Embedded Projects in IoT Technology. And know that embedded projects are not the limitation of an IoT, but an expansion of it. How?
Keep reading.

Top Embedded Projects in IoT Technology

Anything that comes with sensors to transmit data and can connect with the internet falls under IoT Technology. Using this technology, you can remotely control your devices, for instance, you can control the humidity level and temperature of your AC while you’re away.
The following are the top embedded projects in IoT technology.

Smart Energy Monitor Based on IoT

A smart energy monitor is a device that monitors how much energy a particular electronic product is consuming. This way, you can save energy and keep energy consumption in control. A typical energy monitor contains voltage and current sensing units, ADC, and a Raspberry Pi board.

The voltage and current sensing devices offer required input to your system, while ADC and Raspberry PI board serve as the processing unit. You can store the parameters using Adafruit.IO that will help you save the data on the cloud. This means you can access this data anywhere anytime online.

Wi-Fi Range Extender

Wi-Fi range extender project is another remarkable addition to IoT technology. This project, as the name suggests, helps you extend the coverage radius of your Wi-Fi unit. The WiFi router operates within specific premises, when you go out of the range, it’ll show a ‘limited range’ problem which you can combat using a WiFi range extender.
To make this project, you’ll require a Nodemcu ESP8266 which is an IoT development platform that comes with both Arduino’s features and a Wi-Fi module. Moreover, you’ll need Arduino IDE software – an official software to program Arduino board. Next, you’ll need to configure ESP8266 using Flash Download Tool that you can download from their website. If you want to get hands-on experience with an IoT application, I suggest you start with this project.

IoT Based Agriculture Solution

If you think IoT technology is limited to homes and offices only, think again. Since you can use IoT technology to monitor the status of soil in your farm or garden. This project will help you monitor the humidity level of the soil and make a final decision when your farm needs water which it will sprinkle, automatically.

To make this project, you’ll require an Arduino board, relay module, a pair of pipe and a hose, a soil moisture sensor, a solenoid valve, and Bluetooth. I suggest you apply this project to a small plant before applying it on a bigger scale in your garden. It will save you both time and money and a lot of hassle that may trouble you later.

Smart Home Security Project

Smart Home Security Project is designed to keep your home and secure when you’re away or you’re asleep. You can get an instant update of your home in case home security is breached. Arduino UNO is used that acts as the main controller of the entire project. Door and window sensors are used that monitor the presence of human beings, any gas leakage, or fire. The devices and modules used in this project communicate with each other, use sensors to gather data and this data is connected with the internet to perform the required task.

IoT Based Healthcare Project

IoT technology never seizes to spread its wings and provide innumerable benefits to the health sector. This project is used to monitor the current condition of the patient and send the report to the specialized doctor for a quick review. This is helpful especially in case of an emergency since it will save time which you’ll otherwise spend taking the patients to the hospital.

Again, Arduino UNO is used in this project to process and collect the data through sensors. An ESP8266 module is employed for the connection with the internet and all data is uploaded to thingspeak (It is an IoT analytics platform service that helps you monitor and analyze live data streams in the cloud) for remote analysis.

IoT Based Traffic Control Project

Heavy traffic in urban cities is a major concern. Hence it is required to develop an efficient traffic management setup that not only controls the heavy traffic but also informs you about the shortest route being taken. IoT-based traffic control project is used for this purpose. In this project, we use Arduino board and IR sensors to measure the distance. This distance will inform us about any vehicle whether or not it’s near the signal and the traffic lights will be controlled accordingly. IoT devices used in this project include IR-sensors, traffic lights, an Arduino board, and a central server to collect and process data to control the traffic.

IoT Based Waste Management System

Waste management is very challenging in big cities. The reason we require an IoT-based waste management system to effectively dump the garbage. This system includes Arduino UNO that will be interfaced with the ultrasonic sensors that monitor the level of garbage in the bin and inform the municipal web server in case the dustbin is filled.
This is the list of a few IoT-based embedded projects that you can develop based on your requirement. Incorporating embedded devices like Arduino or Raspberry Pi with IoT technology will help you save both time and money, and you can control IoT-based devices anywhere anytime online.
That’s all for today. Hope you’re enjoyed reading this article. If you have any questions, you can approach me in the section below. I’d love to help you the best way I can. Thank you for reading this article.