Class: Senior Secondary School 2 (SS2 / SSS2)
Term: 1st Term
Week: 9
Age: 16 years
Duration: 45 minutes
Subject: Basic Electronics
Curriculum Theme: Electronics Fundamentals
Previous Lesson: Power in AC Circuits: Q Factor and Bandwidth (FH and FL).
Topic: TRANSISTORS
Subject Matter: Meaning of TRANSISTORS (definition of transistor), concept of transistors (basic idea and function), biasing of transistors (setting operating point)

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define a transistor.
Explain the basic concept and function of a transistor.
State the purpose of biasing a transistor.

Affective Domain:

Appreciate the importance of transistors in electronic circuits.
Value the need for proper biasing for stable circuit operation.

Psychomotor Domain:

Draw the symbols for different types of transistors.
Draw common transistor biasing arrangements.

Participate in discussions about transistor operation.
Collaborate with peers to understand transistor concepts.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Basic Electronics for Senior Secondary Schools by [Author/Publisher Name]
https://www.electronics-tutorials.ws/transistor/tran_1.html
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-biasing/

Instructional Materials

The teacher will teach this lesson with the aid of:

Actual transistors (e.g., bipolar junction transistors, field-effect transistors like JFET, MOSFET).
Charts showing pictures of various transistors and their schematic symbols.
Whiteboard and markers.

Rationale for the Lesson

This lesson helps pupils understand transistors, which are fundamental components in almost all modern electronic devices. Understanding transistors enables pupils to grasp how electronic circuits function as switches and amplifiers, preparing them for more advanced electronics studies.

Prerequisite/Previous Knowledge

Pupils should have a basic understanding of semiconductors and diodes from previous lessons.

Lesson Content/Board Summary

TRANSISTORS

Meaning of Transistors

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is one of the fundamental building blocks of modern electronic devices.

Transistors are broadly classified into two main types:

Bipolar Junction Transistors (BJTs): These include NPN and PNP types.
Field-Effect Transistors (FETs): These include Junction FETs (JFETs) and Metal-Oxide-Semiconductor FETs (MOSFETs).

Concept and Function of Transistors

Transistors typically have three terminals:

For BJTs: Base, Collector, and Emitter.
For FETs: Gate, Drain, and Source.

A small signal applied to one terminal (e.g., base for BJT, gate for FET) controls a larger current flowing between the other two terminals (e.g., collector-emitter for BJT, drain-source for FET). This allows transistors to function as:

Amplifiers: Increasing the strength of an electrical signal.
Switches: Turning currents ON or OFF in a circuit.

Transistor Symbols

The following are common transistor schematic symbols:

NPN BJT: (Arrow on emitter points outwards)
PNP BJT: (Arrow on emitter points inwards)
N-channel JFET: (Arrow on gate points inwards)
P-channel JFET: (Arrow on gate points outwards)
N-channel Enhancement MOSFET: (Gate isolated, dashed channel, arrow on substrate or source points inwards)
P-channel Enhancement MOSFET: (Gate isolated, dashed channel, arrow on substrate or source points outwards)

(Teacher to draw these symbols clearly on the board)

Biasing of Transistors

Definition: Biasing refers to the process of setting the DC operating voltage and current levels of a transistor to ensure it operates correctly and stably within its intended region (e.g., active region for amplification, saturation/cutoff for switching).

Purpose of Biasing:

To establish a suitable quiescent (Q) point or operating point.
To ensure linear amplification without distortion when an AC signal is applied.
To stabilize the operating point against variations in temperature or transistor parameters.
To prevent the transistor from going into cutoff or saturation prematurely.

Common Biasing Arrangements:

Fixed Bias (Base Resistor Bias): Simple but unstable with temperature changes.
Collector-to-Base Bias (Feedback Bias): Provides some stability but limited.
Voltage Divider Bias (Emitter Bias): The most widely used and stable biasing method. It uses a voltage divider network at the base to provide a stable base voltage.

(Teacher to draw a simplified Voltage Divider Biasing circuit on the board and label key components like R1, R2, Rc, Re, Vcc)

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them about the basic components of electronic circuits they have learned so far, such as resistors and diodes.
Pupils’ Activity: Pupils respond by mentioning resistors and diodes and their functions.
Learning Point: Pupils recall prior knowledge and are introduced to the lesson topic.

Step 2: Meaning of Transistors

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines a transistor as a semiconductor device used for amplification and switching, and introduces its main types (BJT and FET).
Pupils’ Activity: Pupils listen attentively and note down the definition and types of transistors.
Learning Point: Pupils understand the fundamental definition and classification of transistors.

Step 3: Concept and Function of Transistors

Time: 8 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains the basic concept of how a small signal at one terminal controls a larger current, illustrating its function as an amplifier and a switch using simple analogies.
Pupils’ Activity: Pupils ask questions for clarification and contribute to the discussion on transistor functions.
Learning Point: Pupils grasp the core operational principle of transistors.

Step 4: Transistor Symbols

Time: 7 minutes
Teaching Skill: Demonstration/Drawing
Teacher’s Activity: The teacher draws and explains the schematic symbols for NPN, PNP, JFET, and MOSFET transistors on the board, pointing out key features like the arrow direction.
Pupils’ Activity: Pupils carefully observe the symbols and draw them in their notebooks.
Learning Point: Pupils learn to identify and draw standard transistor symbols.

Step 5: Biasing of Transistors (Purpose)

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher introduces the concept of transistor biasing, explaining its purpose in setting the operating point and ensuring stable, distortion-free operation.
Pupils’ Activity: Pupils listen and understand why biasing is necessary for transistors.
Learning Point: Pupils understand the importance and purpose of biasing in transistor circuits.

Step 6: Biasing of Transistors (Arrangements)

Time: 6 minutes
Teaching Skill: Discussion/Illustration
Teacher’s Activity: The teacher discusses common biasing arrangements such as fixed bias, collector-to-base bias, and voltage divider bias, focusing on the advantages of voltage divider bias.
Pupils’ Activity: Pupils explain the need for different biasing arrangements and draw the voltage divider bias circuit.
Learning Point: Pupils learn about various biasing methods and their applications.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define a transistor.
State two main functions of a transistor.
Draw the schematic symbol for an NPN transistor.
Explain the purpose of biasing a transistor.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson and assigns homework: “Research practical applications of transistors in everyday electronic devices.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and are encouraged to explore further.

Lesson Keywords

Transistor – A semiconductor device used for amplification or switching.
Biasing – Setting the DC operating point of a transistor.
BJT – Bipolar Junction Transistor.
FET – Field-Effect Transistor.
NPN – A type of Bipolar Junction Transistor.
Amplifier – A circuit that increases the strength of a signal.
Switch – A device that opens or closes a circuit.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional information on transistor parameters like current gain (beta) or transconductance. For pupils needing more support, the teacher will provide simplified diagrams and allow more time for drawing and explanation, focusing on the core definitions and functions.

Note for teachers using this lesson plan

Emphasize the practical relevance of transistors by showing actual components. Encourage pupils to draw the symbols and biasing circuits accurately. Use the charts provided in the instructional materials to visually reinforce the concepts. Ensure sufficient time for drawing and question-and-answer sessions.