7404 IC Pinout: Hex Inverter Logic Gate Diagram

The 7404 is one of the simplest ICs in the 7400 TTL logic family -- six NOT gates in a single 14-pin DIP package. It inverts a logic signal: HIGH in gives LOW out, LOW in gives HIGH out. Despite its simplicity, it shows up constantly in real circuits as a signal inverter, logic buffer, oscillator building block, and input conditioning circuit.

This guide covers the 14-pin DIP pinout, the truth table, operating characteristics across TTL and CMOS variants, and practical breadboard uses.

The 14-Pin DIP Pinout

The 7404 is a 14-pin dual in-line package (DIP). Pin 1 is identified by a notch or dot at one end of the package.

        ┌──┬──┐
  1A  1 │  ┴  │ 14  VCC
  1Y  2 │     │ 13  6A
  2A  3 │     │ 12  6Y
  2Y  4 │7404 │ 11  5A
  3A  5 │     │ 10  5Y
  3Y  6 │     │  9  4A
 GND  7 │     │  8  4Y
        └─────┘

Pin 14 = VCC (supply voltage) Pin 7 = GND

Every gate has an input pin (A) and an output pin (Y). Six gates total: 1A/1Y, 2A/2Y, 3A/3Y, 4A/4Y, 5A/5Y, 6A/6Y.

The Most Common Breadboard Mistake

Forgetting to connect VCC and GND. The IC will not work if VCC (pin 14) and GND (pin 7) are not connected even though you have valid logic signals on the input pins. On a breadboard, those two pins commonly sit in the middle of the chip and are easy to overlook.

Truth Table

For each of the six inverter gates:

Input (A) Output (Y)
0 (LOW) 1 (HIGH)
1 (HIGH) 0 (LOW)

That is the complete truth table for a NOT gate. No edge cases.

7404 Variants: TTL vs. CMOS

The "74" prefix covers several logic families with different supply voltage and speed characteristics:

Part Number Family VCC Range Propagation Delay Output Drive
7404 Standard TTL 4.75--5.25V ~22ns 16mA sink
74LS04 Low-Power Schottky 4.75--5.25V ~10ns 8mA sink
74HC04 High-Speed CMOS 2--6V ~7ns at 5V ±25mA
74HCT04 CMOS, TTL-compatible inputs 4.5--5.5V ~7ns ±25mA
74AHC04 Advanced High-Speed CMOS 2--5.5V ~3.5ns ±8mA

For a 5V Arduino or standard TTL breadboard circuit, the 74HC04 or 74HCT04 are the go-to modern replacements for the original 7404. They are faster, run at lower supply voltages, have better drive strength, and are widely available.

For 3.3V systems (ARM microcontrollers, Raspberry Pi GPIO), use the 74HC04 (which works from 2V) rather than the HCT04 (which requires at least 4.5V supply).

Using the 7404 on a Breadboard

Required Connections First

  1. Connect pin 14 (VCC) to the positive supply rail (5V for standard TTL/HCT; 3.3V or 5V for HC).
  2. Connect pin 7 (GND) to the ground rail.
  3. Add a 0.1µF bypass capacitor between VCC (pin 14) and GND as close to the chip as possible. This is not optional on a working prototype -- without it, the switching transients cause glitches on the supply rail that can corrupt nearby logic.

Inverting a Signal

Connect the signal source to any input pin (1A, 2A, ..., 6A). The inverted output appears on the corresponding Y pin.

Example: Arduino digital output to gate 1:

The LED is now active-low -- it illuminates when D7 is LOW.

Using Unused Gates

Unused inputs must not be left floating. A floating TTL input acts as a weak logic HIGH, which may cause the output to oscillate and draw extra supply current. Tie unused inputs to GND (for a permanently HIGH output) or to VCC (permanently LOW output). For CMOS variants (74HC04), floating inputs are more serious -- they can latch-up or draw high current. Always tie them.

Building a Simple RC Oscillator

A single inverter gate can form a crude oscillator with one resistor and one capacitor. Wire it as a Schmitt feedback oscillator:

  1. Connect output (1Y) back to input (1A) through a resistor R (e.g., 10kΩ).
  2. Connect a capacitor C (e.g., 10nF) from the input (1A) to GND.

Approximate frequency: f ≈ 1 / (1.2 × R × C)

For R = 10kΩ, C = 10nF: f ≈ 1 / (1.2 × 10,000 × 0.00000001) ≈ 8.3 kHz.

Note: this calculation assumes the 74HC04, which has a defined input threshold. The standard 7404 has poorly defined thresholds and is not ideal for this oscillator. Use the 74HC04 or the purpose-built 74HC14 (Schmitt trigger inverter) for a more stable oscillator.

Signal Conditioning: Logic Level Translation (Limited)

The 7404 is occasionally used to condition noisy open-collector or open-drain outputs. A 10kΩ pull-up to VCC on the 7404 input, with the open-collector output pulling it low, gives a clean TTL-level signal at the 7404 output.

It does not do full voltage level translation -- for 3.3V to 5V and vice versa, use a dedicated level shifter (BSS138 MOSFET, TXB0104, or similar).

Driving Outputs

Each gate output can sink 16mA (standard 7404) or source/sink 25mA (74HC04). This is enough to drive a single LED directly with a series resistor (see LED circuit article for resistor sizing). For loads beyond 25mA, buffer the output through a transistor or MOSFET.

The output low voltage (Vol) is typically 0.4V for TTL, 0.1V for CMOS -- close enough to GND for downstream logic.

Creating a 7404 Pinout Diagram

CircuitDiagramMaker's IC component tool lets you place a 7404 DIP symbol on a schematic with labeled pins, draw connections to signal sources and loads, and verify the logic flow visually. Useful for documenting any design that uses multiple gates from the same package.

Create your own 7404 pinout diagram -- free

Key Takeaways