Lesson Notes By Weeks and Term v4 - SHS 2
DIGITAL ELECTRONICS
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DIGITAL ELECTRONICS
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Subject: Physics
Class: SHS 2
Term: 2nd Term
Week: 18
Grade code: 2.3.3.LI.3
Strand code: 3
Sub-strand code: 3
Content standard code: 2.3.3.CS.2
Indicator code: 2.3.3.LI.3
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: DIGITAL ELECTRONICS
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Welcome, future engineers and innovators! Look around you. Your smartphone, the traffic lights in our cities like Accra and Kumasi, the digital television in your living room, and even the system that controls the electricity supply (ECG) – they are all built on the principles of digital electronics. These devices make decisions based on simple "Yes" or "No", "On" or "Off" logic, which we represent with the numbers 1 and 0. Today, we will learn the fundamental language that these devices use: Boolean Algebra. Specifically, we will learn how to take a set of desired outcomes (like when a security light should turn on) and translate it into a mathematical expression called the Sum of Products.
Part A: Quick Recap of Basic Logic Gates and Boolean Notation
Before we build complex expressions, let's remember our basic building blocks. In Boolean algebra, variables can only have two values: 1 (HIGH/TRUE/ON) or 0 (LOW/FALSE/OFF).
| Gate | Function | Symbol | Boolean Expression | How to Read It | | :--- | :--- | :--- | :--- | :--- | | NOT | Inverts the input. | | Y = Ā | "Y equals NOT A" | | AND | Output is 1 only if ALL inputs are 1. | | Y = A . B (or Y = AB) | "Y equals A AND B" | | OR | Output is 1 if ANY input is 1. | | Y = A + B | "Y equals A OR B" |
Important Note on Notation: The dot (.) for AND is like multiplication. The plus (+) for OR is like addition. The bar over a variable (e.g., Ā) means "NOT" or "inverted". So if A = 1, then Ā = 0. Part B: What is a Truth Table?