74HC283 — 4-Bit Binary Full Adder with Fast Carry

Overview

The 74HC283 (SN74HC283N) is a 4-bit binary full adder IC with fast internal look-ahead carry generation, manufactured by Texas Instruments, Nexperia, and ON Semiconductor. It adds two 4-bit binary words ( $A_1 \dots A_4$ and $B_1 \dots B_4$ ) plus an incoming carry bit ( $C_0$ ), producing a 4-bit binary sum ( $S_1 \dots S_4$ ) and a final carry-out bit ( $C_4$ ).

Operating from 2.0V to 6.0V DC, the 74HC283 is a staple logic component in computer architecture educational kits, ALU (Arithmetic Logic Unit) designs, breadboard computers (such as SAP-1 / Ben Eater 8-bit computer builds), and high-speed hardware accumulator circuits.

Quick reference


Supply Voltage (`VCC`)	2.0 V to 6.0 V DC
Logic Family	High-Speed CMOS (74HC) / TTL Compatible (74HCT)
Operand Inputs	4-Bit $A$ ( $A_1, A_2, A_3, A_4$ ) & 4-Bit $B$ ( $B_1, B_2, B_3, B_4$ )
Carry Control	Carry In ( $C_0$ ) and Carry Out ( $C_4$ )
Sum Outputs	4-Bit Sum ( $S_1, S_2, S_3, S_4$ )
Propagation Delay	$16\text{ ns}$ typical at $VCC = 4.5\text{V}$
Package	16-pin DIP / SOIC-16 / TSSOP-16

Pinout (DIP-16 Package)

text

             ┌───┴───┐
          S2 1│ 1   16│ VCC (+2V to +6V)
          B2 2│       │15 B3
          A2 3│ 74HC  │14 A3
          S1 4│  283  │13 S3
          A1 5│       │12 A4
          B1 6│       │11 B4
          C0 7│       │10 S4
         GND 8│       │9  C4 (Carry Out)
             └───────┘

Pin	Name	Type	Description
1	`S2`	Output	Sum Bit 2 Output
2	`B2`	Input	Operand B Bit 2 Input
3	`A2`	Input	Operand A Bit 2 Input
4	`S1`	Output	Sum Bit 1 Output (LSB Sum)
5	`A1`	Input	Operand A Bit 1 Input (LSB A)
6	`B1`	Input	Operand B Bit 1 Input (LSB B)
7	`C0`	Input	Carry In (LSB Carry Input)
8	`GND`	Power	Ground reference (0 V)
9	`C4`	Output	Carry Out (MSB Carry Output — Connect to $C_0$ of next 74HC283 for 8-bit adding)
10	`S4`	Output	Sum Bit 4 Output (MSB Sum)
11	`B4`	Input	Operand B Bit 4 Input (MSB B)
12	`A4`	Input	Operand A Bit 4 Input (MSB A)
13	`S3`	Output	Sum Bit 3 Output
14	`A3`	Input	Operand A Bit 3 Input
15	`B3`	Input	Operand B Bit 3 Input
16	`VCC`	Power	Power Supply (+2.0V to +6.0V DC)

Mathematical Operation

The arithmetic addition performed by the chip follows:

$(S_4 S_3 S_2 S_1)_2 + 16 \cdot C_4 = (A_4 A_3 A_2 A_1)_2 + (B_4 B_3 B_2 B_1)_2 + C_0$

For an 8-bit adder, cascade two 74HC283 chips by connecting $C_4$ of the lower nibble adder to $C_0$ of the upper nibble adder.

Subtraction Mode (A - B via Two's Complement)

Invert all $B$ inputs ( $B_1 \dots B_4$ ) using XOR gates (74HC86) driven by a SUB control line, and set $C_0 = 1$ . The adder computes $A + \bar{B} + 1 = A - B$ .

Common mistakes

Leaving Carry In ( $C_0$ , Pin 7) floating: For standard addition, $C_0$ must be tied directly to GND. Leaving $C_0$ floating produces incorrect LSB additions.
Conflating pinout with older 7483 / 74LS83 chips: The 74HC283 has a different, optimized pinout arrangement compared to the legacy 7483/74LS83.

Notes

74HC283 vs 74LS283: 74HC283 is CMOS (low power, 2V-6V supply); 74LS283 is TTL (5V supply only, higher power consumption).