Transistor Amplification Basics

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Questions and Answers

What is the primary function of the conducting layer in OLED technology?

Transport holes from the anode (correct)

Supply negatively charged electrons

Increase power consumption

Prevent water intrusion

What differentiates OLED technology from LCD and PDP in terms of viewing angle?

160 degrees

75-90 degrees

360 degrees

180 degrees (correct)

What is a common disadvantage of OLED technology related to its lifetime?

Limited lifetime of 60,000 hours (correct)

Color shift at the beginning of its lifetime

No color aging issues

Perfect durability over time

Which component is responsible for converting AC to DC in a basic power supply?

Rectifier Signup and view all the answers

What is the function of a voltage regulator in a DC power supply?

Hold the output voltage constant Signup and view all the answers

How can surge current be limited in a power supply system?

Insert a current limiting resistor Signup and view all the answers

What is the primary function of a transistor?

To amplify or switch electronic signals Signup and view all the answers

Which of the following statements about transistors is true?

A transistor generates a larger version of the input voltage Signup and view all the answers

Which terminal of a transistor is typically connected to 0V?

Terminal 2 Signup and view all the answers

What is the term used to describe the amplification or gain provided by a transistor?

Transistor gain Signup and view all the answers

Which type of transistor is most widely used in modern electronics?

MOSFET (Metal–Oxide–Semiconductor Field-Effect Transistor) Signup and view all the answers

What is the primary mechanism that produces light in an LED?

Electron-hole recombination Signup and view all the answers

What is the typical voltage range required for operating an LED?

1.5 - 2.5 V Signup and view all the answers

What is the purpose of using a current-limiting resistor with an LED?

To prevent overloading and potential damage to the LED Signup and view all the answers

What is the primary advantage of COB (Chips On Board) LED technology?

Higher intensity and better uniformity Signup and view all the answers

Which of the following is NOT an organic light-emitting diode (OLED) display technology?

Cathode Ray Tube (CRT) Signup and view all the answers

What is the primary advantage of OLED technology compared to traditional solid-state LEDs?

Simpler manufacturing process Signup and view all the answers

Which of the following statements accurately describes the relationship between transistor beta (β) and alpha (α)?

β represents the current increase from base to collector, while α is the ratio of collector current to emitter current. Signup and view all the answers

In the active region of a transistor, which of the following statements is true?

The base-emitter junction is forward biased, and the collector-base junction is reversed biased. Signup and view all the answers

What is the primary function of a light-emitting diode (LED)?

To convert electrical energy into light energy. Signup and view all the answers

In the saturation region of a transistor, which of the following statements is true?

Both the base-emitter and collector-base junctions are forward biased. Signup and view all the answers

Which of the following is NOT a type of LED mentioned in the text?

Filament Signup and view all the answers

In the cutoff region of a transistor, what is the value of the collector current (Ic)?

Ic = 0A Signup and view all the answers

Study Notes

PN Junction and LED

A PN junction has a lot of electrons and holes at the junction due to excitation.
Electrons from the n-side need to be injected to the p-side to promote recombination.
The junction is biased to produce even more e-h pairs and to inject electrons from the n-side to the p-side for recombination to happen.
Recombination produces light, with a visible wavelength of 390-770nm.

LED Characteristics and Connection

An LED requires 1.5-2.5V direct or 10mA current source.
To prevent overloading, use current limiting resistors.
COB (Chips On Board) refers to the mounting of a bare LED chip in direct contact with a substrate to produce LED arrays.
COB has advantages such as compactness, high-intensity, high uniformity, design simplicity, and superior thermal performance.

Display Technologies

Display technologies include:
- Cathode Ray Tube (CRT)
- Vacuum Fluorescent Display (VFD)
- Field Emission Display (FED)
- Liquid Crystal Display (LCD)
- Plasma Display Panel (PDP)
- Electroluminescent Display (EL)
- Organic Light Emitting Diode (OLED)

OLED

OLED is also known as light emitting polymer (LEP) and organic electro luminescence (OEL).
OLED has an emissive electroluminescent layer composed of a film or organic compound.
When electrical current is applied, a bright light is emitted.
OLED is 100-500 nanometers thick, about 200 times smaller than a human hair.
OLED architecture consists of:
- Cathode: supplies negatively charged electrons
- Emissive layer (EML): where the electron-hole recombination takes place

Transistor

BJT (Bipolar Junction Transistor) is a current-controlled device.
BJT contains two PN junctions: base-emitter junction and collector-base junction.
Transistor current gain (β) is the current increase from base to the collector.
Alpha (α) is the ratio of the collector current to emitter current, also known as collector current efficiency.

Transistor Operating Regions

Cutoff: both junctions are reversed biased.
Saturation: both junctions are forward biased.
Active: the base-emitter junction is forward biased while the collector-base junction is reversed biased.

Transistor Characteristics

Saturation characteristics:
- Base-emitter junction and base-collector junction are both forward biased.
- Transistor is ‘FULLY ON’ (saturation region).
- Max collector current flows (IC = Vcc/RL).
Cutoff characteristics:
- Base-emitter and collector-base junctions are both reversed biased.
- Transistor is ‘FULLY OFF’ (cutoff region).
- No collector current flows (Ic = 0A).

Power Supply

Power supply is a device that produces DC of a particular voltage and current from a source of electricity.
Power conversion types:
- AC/DC
- DC/AC (inverter)
- DC/DC (converter)
Functions of power supply:
- Voltage transformation
- Rectification
- Filtering
- Regulation
- Isolation
- Protection
Back-up power components:
- Transformer
- Rectifier
- Filter
- Regulator
- Elements of power supply
Linear power supply types:
- Unregulated
- Regulated
- Switching power supply (SMPS)

Linear Power Supply Components

Transformer: an electrical device that makes use of electromagnetic induction to transfer current from one circuit to another.
Rectifier: converts AC to DC.
Filter: reduces the voltage and current variations in the output from a rectifier.
Regulator: reduces the ripple in the filter output voltage.

Voltage Regulator

The final circuit in the DC power supply.
A device used to hold the output voltage from a DC power supply relatively constant over a specified range of line and load variations.
Linear IC voltage regulator is a device used to hold the output voltage from a DC power supply relatively constant.

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Description

Learn about the fundamentals of transistor amplification. Understand how a transistor functions as a 3-terminal semiconductor device, its role in amplifying or switching signals, and the concept of gain in transistor amplifiers.