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.3
Strand code: 4
Sub-strand code: 2
Content standard code: 2.5.2.CS.1
Indicator code: 2.5.2.LI.3
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRONIC COMPONENTS AND CIRCUITS
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This lesson introduces one of the most important building blocks in modern electronics: the Operational Amplifier, or "Op-Amp". Think about the sound systems used at church, in a community information centre, or by your favourite DJ ("spinner"). The ability to take a small, weak signal (like from a microphone or a phone) and make it loud and strong is thanks to amplifiers. The Op-Amp is the "brain" inside many of these amplifier circuits. It is a tiny chip with a powerful job. Today, we will focus on two very common Op-Amp Integrated Circuits (ICs), the 741 and the 4558, learning how to identify their parts (pins) and understand the basic rules that make them work.
What is an Operational Amplifier (Op-Amp)? An Operational Amplifier is a type of Integrated Circuit (IC). An IC, or "chip," is a tiny electronic device that contains many transistors, resistors, and capacitors all built on a small piece of silicon.
An Op-Amp is a special type of amplifier with two inputs and one output. Its main job is to amplify the difference between the voltages at its two inputs. It has a very, very high gain, which means it can make a very small input signal voltage much, much larger at the output. The Op-Amp Symbol In circuit diagrams (schematics), we don't draw all the internal transistors. We use a simple triangular symbol: Non-inverting Input (+): An input signal applied here will appear at the output with the same polarity (in-phase). Inverting Input (-): An input signal applied here will appear at the output with the opposite polarity (inverted or 180° out-of-phase). Output (Vout): This is where the amplified signal comes out. Positive Power Supply (+Vcc or +Vs): The positive voltage needed to power the IC. Negative Power Supply (-Vee or -Vs): The negative voltage needed to power the IC. Op-Amps usually require a dual or split power supply (e.g., +12V and -12V). Principle of Operation: The Comparator The fundamental rule of an Op-Amp is: Vout = A * (V+ - V-) Where: `Vout` is the output voltage. `A` is the Open-Loop Gain (which is extremely large, often over 100,000). `V+` is the voltage at the non-inverting input. `V-` is the voltage at the inverting input.
Because the gain (A) is so huge, the Op-Amp essentially acts like a comparator when used without feedback: If V+ is slightly greater than V-, the output `Vout` swings to its maximum positive voltage (close to +Vcc). If V- is slightly greater than V+, the output `Vout` swings to its maximum negative voltage (close to -Vee).
This high-gain behaviour is usually "tamed" by using a feedback loop (connecting a resistor from the output back to the inverting input), which makes the Op-Amp a stable and predictable amplifier. Focus IC 1: The 741 Op-Amp (Single Op-Amp) The `µA741` or simply `741` is a classic, general-purpose single Op-Amp. It comes in an 8-pin package called a DIP (Dual In-line Package).