Lesson Notes By Weeks and Term v4 - SHS 3
APPLICATIONS OF ELECTRONICS
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APPLICATIONS OF ELECTRONICS
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Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 14
Grade code: 3.3.4.LI.2
Strand code: 3
Sub-strand code: 4
Content standard code: 3.3.4.CS.2
Indicator code: 3.3.4.LI.2
Theme: ELECTRIC FIELD, MAGNETIC FIELD AND ELECTRONICS
Subtheme: APPLICATIONS OF ELECTRONICS
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This lesson introduces one of the most fundamental and powerful applications of electronics: the amplifier. In our daily lives in Ghana, we are constantly surrounded by amplifiers. Think about the sound system at a school assembly, the music playing from a speaker at a community event, the ability of a radio to pick up a weak signal from a station in Accra, or how your mobile phone makes a distant voice clear. All these technologies rely on the principle of amplification – taking a small, weak electrical signal and making it much larger and stronger.
A. What is Amplification? Amplification is the process of increasing the strength (amplitude) of a signal. A signal is a varying quantity, like the voltage from a microphone that changes with the sound of your voice. An amplifier takes this small, varying input voltage and produces a larger, varying output voltage that is a faithful copy of the input.
The "size" of the amplification is called gain. Voltage gain ($A_v$) is the ratio of the output voltage to the input voltage. $$ A_v = \frac{V_{out}}{V_{in}} $$ If an amplifier has a voltage gain of 100, a 10 mV input signal will become a 1000 mV (or 1V) output signal. B. The NPN Transistor: The Heart of the Amplifier A transistor is a semiconductor device with three terminals: the Base (B), the Collector (C), and the Emitter (E). We will focus on the NPN type.
Think of a transistor like a tap controlling water flow: The Emitter (E) is the source of the water (charge carriers). The Collector (C) is where the water is collected. The Base (B) is the handle of the tap.
A very small effort to turn the handle (a small base current, $I_B$) can control a much larger flow of water from the source to the collection point (a large collector current, $I_C$).