Lesson Notes By Weeks and Term v4 - SHS 3
ELECTRONIC COMPONENTS AND CIRCUITS
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ELECTRONIC COMPONENTS AND CIRCUITS
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Subject: Applied Technology
Class: SHS 3
Term: 2nd Term
Week: 15
Grade code: 2.5.2.LI.4
Strand code: 4
Sub-strand code: 2
Content standard code: 2.5.2.CS.1
Indicator code: 2.5.2.LI.4
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRONIC COMPONENTS AND CIRCUITS
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This lesson introduces the Operational Amplifier (Op-Amp), one of the most versatile and important building blocks in modern electronics. Op-Amps are tiny integrated circuits (ICs) that can be used to build a huge variety of useful circuits. In Ghana, you find them everywhere: in the sound systems used at church or parties, in the control circuits for automatic streetlights, in medical equipment at hospitals like Korle-Bu, and even in your own phone charger. By understanding how Op-Amps work, you will gain the power to design and build circuits that can amplify signals, compare voltages, and even perform mathematical operations.
2.1 What is an Operational Amplifier (Op-Amp)?
An Op-Amp is a high-gain, direct-coupled (DC) amplifier that has two inputs (one inverting, one non-inverting) and a single output. It is the core component of many analogue electronic circuits. Think of it as a very powerful engine for manipulating voltages.
The Op-Amp Symbol: Non-Inverting Input (+): A signal applied here appears at the output with the same polarity (in-phase). Inverting Input (-): A signal applied here appears at the output with the opposite polarity (180° out-of-phase). Output (Vout): The output voltage of the amplifier. Positive Power Supply (+Vcc or +Vs): The positive voltage needed to power the Op-Amp. Negative Power Supply (-Vee or -Vs): The negative voltage needed to power the Op-Amp. This is often called a "dual" or "split" power supply. 2.2 The "Golden Rules" of an Ideal Op-Amp
To simplify circuit analysis, we assume the Op-Amp is "ideal". This gives us two very important rules: Rule 1: The inputs draw no current. The input impedance is infinitely high, so no current flows into the (+) or (-) terminals. (In reality, a tiny current flows, but it's small enough to ignore for most calculations). Rule 2: The Op-Amp will do whatever it can to make the voltage at the two inputs equal. If the circuit has negative feedback (a connection from the output back to the inverting (-) input), the Op-Amp will adjust its output voltage (Vout) until the voltage at the inverting input (V-) is exactly equal to the voltage at the non-inverting input (V+). This is the most crucial concept for understanding amplifier circuits. 2.3 Common Op-Amp ICs: 741 and 4558 μA741: This is a classic, general-purpose single Op-Amp. It comes in an 8-pin package. It is very popular for learning and simple projects. RC4558 or JRC4558: This is a dual Op-Amp IC, meaning it contains two independent Op-Amps in a single 8-pin package. This is very efficient for circuits that need two amplifiers, like stereo audio equipment.