4-Bit Adder Using SN74LS83 IC

Build a 4-bit binary adder using the dedicated SN74LS83 adder IC—all four full adders in one chip!

Overview

After building a 4-bit adder from individual gates, appreciate the convenience of the SN74LS83—a dedicated 4-bit binary full adder IC. It contains four full adders with internal carry propagation, all in a 16-pin package. This single chip replaces dozens of gates and performs the same function as your gate-based adder!

Components Needed

  • 1x SN74LS83 IC
  • 5x LED
  • severalx Wires

Instructions

  1. Gather Your Components

    You need the SN74LS83 4-bit adder IC, 5 LEDs (4 for sum, 1 for carry), wires, breadboard, and 5V power. The 4-bit switch tool and 7-segment display are helpful additions.

  2. Reference Tools

    For testing, you'll want the 4-bit switch tool for inputs and optionally the BCD 7-segment display for decimal output.

  3. Identify the SN74LS83

    The 74LS83 is a 16-pin DIP. Pin 16 is VCC (5V), pin 8 is GND. Inputs A1-A4 and B1-B4 feed the two numbers. C0 is carry-in. Outputs Σ1-Σ4 are sum bits, C4 is carry-out.

  4. Wire the Adder Circuit

    Place the IC on the breadboard. Connect pin 16 to 5V and pin 8 to ground. Connect inputs A1-A4 and B1-B4 to your switches (or the switch tool). Tie C0 to ground for normal addition. Connect Σ1-Σ4 and C4 to LEDs.

  5. Finished Project View

    Here's the completed circuit ready for testing with the switch tools connected.

  6. Test: 0001 + 0000 = 00001

    Top switches: 0001 (decimal 1), Bottom: 0000 (decimal 0). Result: 1 LED lit showing 00001 (decimal 1).

  7. Test: 0001 + 0001 = 00010

    Both inputs: 0001 (decimal 1 each). Result: 00010 (decimal 2). The second LED lights.

  8. Test: 1001 + 1001 = 10010

    Both inputs: 1001 (decimal 9 each). Result: 10010 (decimal 18). Note the 5th bit carry!

  9. Test: 1111 + 1011 = 11010

    Top: 1111 (decimal 15), Bottom: 1011 (decimal 11). Result: 11010 (decimal 26).

  10. Test: 0110 + 0111 = 01101

    Top: 0110 (decimal 6), Bottom: 0111 (decimal 7). Result: 01101 (decimal 13).

  11. Add 7-Segment Display

    Connect the sum outputs to the BCD 7-segment display to see results as decimal digits. For results 0-9, you'll see proper numbers; larger results show special characters.

Challenges

  • Cascade two 74LS83s for 8-bit addition (connect C4 of first to C0 of second)
  • Build a subtractor using complement input and setting C0=1
  • Compare the gate count to your discrete gate adder
  • Add overflow detection for signed arithmetic