7403 IC – Quad 2-Input NAND Gates (DIP-14)
🔲 7403 IC – Quad 2-Input NAND Gates with Open-Collector Outputs (DIP-14)
The 7403 is a TTL logic IC that contains four independent 2-input NAND gates with open-collector outputs, allowing for wired-AND connections and external pull-up resistor configurations. It is ideal for interfacing with different voltage levels, driving LEDs or relays, and logic systems requiring active-low outputs.
⚙️ Technical Specifications
| Parameter | Value |
|---|---|
| Logic Family | TTL (74 series) |
| Function | Quad 2-input NAND (open-collector) |
| Package | DIP-14 |
| Supply Voltage (Vcc) | 4.75V to 5.25V |
| Output Type | Open-Collector |
| Max Output Sink Current | 16 mA |
| Input Logic Levels | Low ≤ 0.8V, High ≥ 2V |
| Output Voltage (max) | Dependent on pull-up resistor and external Vcc |
📌 Pin Configuration (DIP-14)
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | A1 (Input) | 14 | Vcc (Power) |
| 2 | B1 (Input) | 13 | B4 (Input) |
| 3 | Y1 (Output) | 12 | A4 (Input) |
| 4 | A2 (Input) | 11 | Y4 (Output) |
| 5 | B2 (Input) | 10 | B3 (Input) |
| 6 | Y2 (Output) | 9 | A3 (Input) |
| 7 | GND (Ground) | 8 | Y3 (Output) |
🔍 What is Open-Collector?
Open-collector outputs do not drive high, they only pull low (sink current). You must use an external pull-up resistor to define the HIGH state. This makes the 7403 ideal for:
Wired-AND logic
Level shifting
Driving higher voltage loads
Bus sharing between devices
🧠 Truth Table (Per NAND Gate)
| A | B | Output Y |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 (pulled low by transistor) |
Note: When output = 1, the transistor is OFF, and the output is pulled HIGH by the resistor.
🛠️ Applications
Interfacing logic levels between 5V and 12V systems
Driving LEDs, relays, or motors
Bus arbitration systems
Custom pull-up logic networks
Logic experiments and education