FA 8 bit

8-bit Full Adder (Transistor-Level Design)

📌 Overview

This project presents the design and implementation of an 8-bit full adder using discrete transistor-based logic gates. The system is built by cascading multiple 1-bit full adder units constructed from basic logic gates (XOR, AND, OR).

The project demonstrates a complete workflow from circuit design and PCB layout to physical implementation and verification.

🧠 Design Concept

A full adder computes the sum of three input bits:

• A
• B
• Carry-in (Cin)

Logic equations:

S = A ⊕ B ⊕ Cin
Cout = AB + Cin(A ⊕ B)

The 8-bit adder is implemented using a ripple-carry architecture, where the carry output of each stage propagates to the next stage.

🖥️ PCB Design

PCB Layout

3D View

🛠️ Hardware Implementation

Top View

Stack View

🧪 Simulation Results

Input Signals

Output Signals

🎥 Demo Video

Watch demo on YouTube

📂 Project Structure

8bit-full-adder/
├── README.md
├── images/
│   ├── pcb/
│   ├── hardware/
│   ├── waveform/
│   └── schematic/
├── kicad_project/
├── docs/

⚙️ How to View the Project (KiCad)

⚠️ Important: To correctly view the schematic and PCB, you must open the KiCad project file.

Steps:

1. Install KiCad (https://www.kicad.org/)
2. Open KiCad
3. Click File → Open Project
4. Navigate to:

kicad_project/

5. Open the file:

*.kicad_pro

Then:

• Open Schematic Editor → to view circuit design
• Open PCB Editor → to view PCB layout

⚠️ Do NOT open .kicad_sch or .kicad_pcb directly, as some links may not load correctly.

🧩 Features

• Transistor-level implementation of logic gates
• Modular design (XOR, AND, OR blocks)
• 8-bit ripple-carry architecture
• Full PCB design and fabrication
• Real hardware verification

🚀 Future Improvements

• Optimize PCB layout for reduced size
• Extend functionality to support subtraction (designing an adder-subtractor circuit)
• Optimize circuit design to reduce component count and improve efficiency

📖 Documentation

Detailed explanation is available in:

docs/project_overview.md

👨‍💻 Author

• Hoang Cao Tri — Team Project
• University of Science, VNU-HCM

📌 Notes

This project is intended for educational purposes and demonstrates fundamental concepts in digital logic design and hardware implementation.