Week 5

Circuit

Assignment Description

This assignment focuses on designing and implementing basic digital logic gates (NOT, AND, and OR) using transistors. The project aims to demonstrate how transistors function as electronic switches to perform logical operations, forming the fundamental building blocks of digital computers.

Objectives

Practical Application: Applying theoretical circuit concepts learned in class through hands-on practice.

Transistor Mastery: Understanding the functions, operating modes, and practical benefits of transistors in electronic circuits.

Circuit Assembly: Developing the ability to accurately wire and troubleshoot complex electronic circuits on a breadboard.

Tools & Components

Breadboard
Transistors
9V Battery
Resistors
3 LEDs
Pushbuttons
Jumper Wires

1. The NOT Gate (The Inverter)

Circuit Logic

The NOT gate is known as an "Inverter." Its function is to reverse the input signal: if the input is HIGH (1), the output is LOW (0), and vice versa. In this circuit, the transistor acts as a switch that shorts the output to the ground when activated.

Implementation StepsLogic

System Understanding: Analyze the NOT gate truth table and understand how the transistor will bypass the current.
Virtual Simulation: Design and test the circuit on TinkerCad to ensure the logic is correct before physical assembly.
Component Preparation: Gather the BC547 transistor, 1kΩ base resistor, 220Ω LED resistor, and the LED.
Practical Execution: Connect the transistor's emitter to the ground, the collector to the LED, and the base to the switch. When the switch is pressed, the LED should turn off.

2. The AND Gate

The AND gate only produces a HIGH output (1) if both inputs are HIGH. In a transistor circuit, this is achieved by connecting two transistors in "Series." The current cannot reach the LED unless both transistors are switched ON.

Implementation StepsLogic

System Understanding: Realize that the circuit requires a complete path through two switches.
Virtual Simulation: Use TinkerCad to verify that pressing only one button does not light the LED.
Component Preparation: Prepare two transistors, two pushbuttons, and the necessary resistors (1kΩ and 220Ω).
Practical Execution: Connect the collector of the first transistor to the emitter of the second. Connect the output (LED) to the collector of the second transistor.

3. The OR Gate

The OR gate produces a HIGH output (1) if at least one of the inputs is HIGH. This is implemented by connecting two transistors in "Parallel." If either transistor is activated, the current will find a path to the LED.

Implementation StepsLogic

System Understanding: Study the parallel connection logic where multiple paths lead to the same output.
Virtual Simulation: Confirm on TinkerCad that any single input (or both) activates the LED.
Component Preparation: Gather two transistors and ensure the resistors match the 9V power supply requirements.
Practical Execution: Connect the collectors of both transistors together and to the LED, while connecting the emitters to the ground.

Critical Considerations

Correct Transistor Selection: Ensure using the correct NPN transistor (e.g., BC547) and identifying its pins (E, B, C) correctly.

Resistor Verification: Double-check resistor values (220Ω for LED protection and 1kΩ for the Base) to avoid burning components.

Secure Wiring: Ensure all jumper wires are firmly pressed into the breadboard to prevent loose connections.

Professional Tips

Cable Management: Avoid using long, messy wires that make the circuit confusing. Use small, pre-cut jumper wires to keep the breadboard clean and readable.

Component Trimming: Resistor legs are often too long and unstable. Use Electronic Diagonal Cutters to trim the legs to a shorter, more manageable length for better stability on the breadboard.

Page updated

Google Sites

Report abuse