The Function and Applications for Bipolar Junction Transistors
My intent here is to focus as exclusively as possible on the practical function and application of bipolar transistors, rather than to explore the quantum world of semiconductor theory. Discussions of holes and electrons are better left to another chapter in my opinion. Here I want to explore how to use these components, not analyze their intimate internal details. I don’t mean to downplay the importance of understanding semiconductor physics, but sometimes an intense focus on solid-state physics detracts from understanding these devices’ functions on a component level. In taking this approach, however, I assume that the reader possesses a certain minimum knowledge of semiconductors: the difference between “P” and “N” doped semiconductors, the functional characteristics of a PN (diode) junction, and the meanings of the terms “reverse biased” and “forward biased.” If these concepts are unclear to you, it is best to refer to earlier chapters in this book before proceeding with this one.
BJT Layers
A bipolar transistor consists of a three-layer “sandwich” of doped (extrinsic) semiconductor materials, (a and c) either P-N-P or N-P-N (b and c ). Each layer forming the transistor has a specific name, and each layer is provided with a wire contact for connection to a circuit. The schematic symbols are shown in the figure (a) and (c).
BJT transistor: (a) PNP schematic symbol, (b) layout (c) NPN schematic symbol, (d) layout
Figure 1. BJT transistor: (a) PNP schematic symbol, (b) layout, (c) NPN schematic symbol, and (d) layout.
The functional difference between a PNP transistor and an NPN transistor is the proper biasing (polarity) of the junctions when operating.
Bipolar transistors work as current-controlled current regulators. In other words, transistors restrict the amount of current passed according to a smaller, controlling current. The main current that is controlled goes from collector to emitter, or from emitter to collector, depending on the type of transistor it is (NPN or PNP, respectively). The small current that controls the main current goes from base to emitter or from emitter to base, once again depending on the kind of transistor it is (NPN or PNP, respectively). According to the standards of semiconductor symbology, the arrow always points in the direction of the current flow.
Figure 2. The direction of the small, controlling current and the large controlled current for (a) a PNP and (b) an NPN transistor.
Bipolar Transistors Contain Two Types of Semiconductor Material
Bipolar transistors are called bipolar because the main flow of current through them takes place in two types of semiconductor material: P and N, as the main current goes from emitter to collector (or vice versa). In other words, two types of charge carriers—electrons and holes—comprise this main current through the transistor.
As you can see, the controlling current and the controlled current always mesh together through the emitter wire, and their currents flow in the direction of the transistor’s arrow. This is the first and foremost rule in the use of transistors: all currents must be going in the proper directions for the device to work as a current regulator. The small, controlling current is usually referred to simply as the base current because it is the only current that goes through the base wire of the transistor. Conversely, the large, controlled current is referred to as the collector current because it is the only current that goes through the collector wire. The emitter current is the sum of the base and collector currents, in compliance with Kirchhoff’s Current Law.
No current through the base of the transistor shuts the transistor off like an open switch and prevents current through the collector. A base current turns the transistor on like a closed switch and allows a proportional amount of current through the collector. The collector current is primarily limited by the base current, regardless of the amount of voltage available to push it.
My intent here is to focus as exclusively as possible on the practical function and application of bipolar transistors, rather than to explore the quantum world of semiconductor theory. Discussions of holes and electrons are better left to another chapter in my opinion. Here I want to explore how to use these components, not analyze their intimate internal details. I don’t mean to downplay the importance of understanding semiconductor physics, but sometimes an intense focus on solid-state physics detracts from understanding these devices’ functions on a component level. In taking this approach, however, I assume that the reader possesses a certain minimum knowledge of semiconductors: the difference between “P” and “N” doped semiconductors, the functional characteristics of a PN (diode) junction, and the meanings of the terms “reverse biased” and “forward biased.” If these concepts are unclear to you, it is best to refer to earlier chapters in this book before proceeding with this one.
BJT Layers
A bipolar transistor consists of a three-layer “sandwich” of doped (extrinsic) semiconductor materials, (a and c) either P-N-P or N-P-N (b and c ). Each layer forming the transistor has a specific name, and each layer is provided with a wire contact for connection to a circuit. The schematic symbols are shown in the figure (a) and (c).
BJT transistor: (a) PNP schematic symbol, (b) layout (c) NPN schematic symbol, (d) layout
Figure 1. BJT transistor: (a) PNP schematic symbol, (b) layout, (c) NPN schematic symbol, and (d) layout.
The functional difference between a PNP transistor and an NPN transistor is the proper biasing (polarity) of the junctions when operating.
Bipolar transistors work as current-controlled current regulators. In other words, transistors restrict the amount of current passed according to a smaller, controlling current. The main current that is controlled goes from collector to emitter, or from emitter to collector, depending on the type of transistor it is (NPN or PNP, respectively). The small current that controls the main current goes from base to emitter or from emitter to base, once again depending on the kind of transistor it is (NPN or PNP, respectively). According to the standards of semiconductor symbology, the arrow always points in the direction of the current flow.
Figure 2. The direction of the small, controlling current and the large controlled current for (a) a PNP and (b) an NPN transistor.
Bipolar Transistors Contain Two Types of Semiconductor Material
Bipolar transistors are called bipolar because the main flow of current through them takes place in two types of semiconductor material: P and N, as the main current goes from emitter to collector (or vice versa). In other words, two types of charge carriers—electrons and holes—comprise this main current through the transistor.
As you can see, the controlling current and the controlled current always mesh together through the emitter wire, and their currents flow in the direction of the transistor’s arrow. This is the first and foremost rule in the use of transistors: all currents must be going in the proper directions for the device to work as a current regulator. The small, controlling current is usually referred to simply as the base current because it is the only current that goes through the base wire of the transistor. Conversely, the large, controlled current is referred to as the collector current because it is the only current that goes through the collector wire. The emitter current is the sum of the base and collector currents, in compliance with Kirchhoff’s Current Law.
No current through the base of the transistor shuts the transistor off like an open switch and prevents current through the collector. A base current turns the transistor on like a closed switch and allows a proportional amount of current through the collector. The collector current is primarily limited by the base current, regardless of the amount of voltage available to push it.
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Forwarded from Engineering Update
Power MOSFET is .....
Anonymous Quiz
44%
Voltage control Device
21%
Current control Device
32%
Both 1 & 2
3%
None of above
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Forwarded from Engineering Update
What type of circuit do we find in our houses?
Anonymous Quiz
55%
Parallel
19%
Series
21%
Series-Parallel
4%
Star-Delta
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🔺 Basic electronics cheat sheet
A small A4-format cheat sheet with the most basic information from the electrical engineering course which includes basic electric components and formulas.
#cheatsheet #electronics
Like share and support 🙏👍👍😍😍🤩
A small A4-format cheat sheet with the most basic information from the electrical engineering course which includes basic electric components and formulas.
#cheatsheet #electronics
Like share and support 🙏👍👍😍😍🤩
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Here are some notes about MOSFETs:
Structure
A MOSFET is a four-terminal device with terminals called the source, drain, gate, and body. The body is usually connected to the source terminal, making it a three-terminal device in appearance.
Working
A MOSFET works by varying the width of a channel where charge carriers flow. The width of the channel is controlled by the voltage applied to the gate, which is located between the source and the drain.
Uses
MOSFETs are used in both analog and digital circuits. They are the most common type of transistor because they use less power, have higher switching speeds, and can be miniaturized easily.
Small-signal analysis
In small-signal analysis, a small AC signal is applied on top of the DC bias voltage. The resulting output AC voltage is amplified based on the slope of the transfer characteristic at the bias point.
Drain punch-through
Drain punch-through can lead to leakage or breakdown between the source and the drain. This can cause loss of gate control.
Structure
A MOSFET is a four-terminal device with terminals called the source, drain, gate, and body. The body is usually connected to the source terminal, making it a three-terminal device in appearance.
Working
A MOSFET works by varying the width of a channel where charge carriers flow. The width of the channel is controlled by the voltage applied to the gate, which is located between the source and the drain.
Uses
MOSFETs are used in both analog and digital circuits. They are the most common type of transistor because they use less power, have higher switching speeds, and can be miniaturized easily.
Small-signal analysis
In small-signal analysis, a small AC signal is applied on top of the DC bias voltage. The resulting output AC voltage is amplified based on the slope of the transfer characteristic at the bias point.
Drain punch-through
Drain punch-through can lead to leakage or breakdown between the source and the drain. This can cause loss of gate control.
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📔 Electronic schematic cheat sheet
This cheat sheet would be very useful to those trying to study electronic components. It can be printed as a poster or as a classic A4 cheat sheet. Would be very useful for reading electric schematics.
#cheatsheet #electronics
This cheat sheet would be very useful to those trying to study electronic components. It can be printed as a poster or as a classic A4 cheat sheet. Would be very useful for reading electric schematics.
#cheatsheet #electronics
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Basics of differential protection relays pdf 🤩🤩💖🥰👍👏
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Basics Of Differential Protection Relays .pdf
2.9 MB
Share 'Basics Of Differential Protection Relays .pdf'
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Forwarded from Engineering Update
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