7404 IC Pin Diagram: Complete Hex Inverter Pinout for the 74LS04 and 74HC04

7404 IC Pin Diagram: Complete Hex Inverter Pinout for the 74LS04 and 74HC04 — interactive diagram. Open it in the editor to customise components and wiring.

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The 7404 IC is a hex inverter containing six independent NOT gates in a 14-pin DIP package, with pin 7 as GND and pin 14 as VCC — a cornerstone of TTL and CMOS digital logic design.

The 7404 is one of the most fundamental integrated circuits in digital electronics. It contains six independent single-input inverter (NOT) gates in a standard 14-pin dual-in-line package (DIP-14). Each gate receives a logic-level input and produces the complemented output: a logic HIGH input produces a logic LOW output, and vice versa.

Pin assignments are fixed by the 7400-series standard. Pin 7 is GND (logic ground / VSS). Pin 14 is VCC (positive supply). The six inverter gates are distributed symmetrically around the remaining twelve pins:

Gate 1: input on pin 1, output on pin 2. Gate 2: input on pin 3, output on pin 4. Gate 3: input on pin 5, output on pin 6. Gate 4: input on pin 9, output on pin 8. Gate 5: input on pin 11, output on pin 10. Gate 6: input on pin 13, output on pin 12.

The symmetrical layout places gates 1–3 on the left side and gates 4–6 on the right side, with outputs and inputs alternating along each side. Note that gates 4–6 have their outputs at lower pin numbers than their inputs — pin 8 (output) and pin 9 (input) — which is a common source of wiring errors.

The 7404 exists in multiple logic families. The original bipolar TTL 7404 operates on 5 V with typical propagation delay of 22 ns. The 74LS04 (Low-power Schottky) reduces power consumption significantly. The 74HC04 (High-speed CMOS) operates over a 2 V to 6 V supply range with very low quiescent current and improved noise margins. The 74HCT04 is CMOS with TTL-compatible input thresholds, useful for interfacing 3.3 V microcontrollers to legacy TTL signals. Always verify the specific family's supply voltage range and I/O voltage levels before mixing families in a design.

Unused inverter inputs must not be left floating. A floating TTL input defaults high due to internal pull-up, but a floating CMOS input oscillates unpredictably, increasing power consumption and generating EMI. Tie unused inputs to VCC or GND as appropriate.

How to wire 7404 ic pin diagram

Identify pin 1 on the physical IC Locate the index notch at one end of the DIP package. With the notch pointing to your left and the package body horizontal, pin 1 is the bottom-left pin. Confirm by finding the small dot or bevelled corner on the package body near pin 1.
Connect VCC to pin 14 and GND to pin 7 Connect the positive supply rail to pin 14 (VCC) and the 0 V ground rail to pin 7 (GND). Add a 100 nF ceramic decoupling capacitor between these pins, placed as close to the IC body as possible to suppress supply-rail transients.
Connect the input signal to the appropriate gate input pin Identify which gate (1 through 6) you will use and connect the digital input signal to its input pin. Gate 1 uses pin 1, Gate 2 uses pin 3, Gate 3 uses pin 5, Gate 4 uses pin 9, Gate 5 uses pin 11, Gate 6 uses pin 13.
Read the inverted output from the gate output pin The complemented output is available at the gate's output pin. Gate 1 output is pin 2, Gate 2 output is pin 4, Gate 3 output is pin 6, Gate 4 output is pin 8, Gate 5 output is pin 10, Gate 6 output is pin 12.
Tie all unused gate inputs to VCC or GND Connect any unused inverter input pins to a defined logic level. Tie to GND (logic LOW) if a steady LOW input is appropriate, or to VCC (logic HIGH) if a HIGH is needed. This prevents oscillation and EMI from floating CMOS inputs.
Verify operation with a logic probe or oscilloscope Apply a known logic level (e.g., press a pull-down push button to generate a LOW) to the gate input and confirm the output is at the complemented level. Use a logic probe or oscilloscope to verify output voltage levels are within the family's specified output voltage range.

Specifications

Package type	14-pin DIP (2.54 mm pitch)
Number of gates	6 independent NOT (inverter) gates
GND pin	Pin 7
VCC pin	Pin 14
Supply voltage — 74LS04	4.75 V to 5.25 V (nominal 5 V)
Supply voltage — 74HC04	2.0 V to 6.0 V
Propagation delay — 74LS04 (typ.)	9 ns at 5 V
Propagation delay — 74HC04 (typ.)	7 ns at 5 V

Safety warnings

Never exceed the maximum supply voltage for the device family. The 74LS04 absolute maximum VCC is 7 V; the 74HC04 absolute maximum is 7 V. Exceeding these limits will permanently damage the IC.
Do not connect 5 V TTL-level signals directly to the inputs of a 3.3 V-supplied 74HC04. Input voltages above VCC + 0.5 V will damage the device through the internal ESD protection diodes. Use a voltage divider or level-shifter IC.
Observe ESD precautions when handling CMOS variants (74HC04, 74HCT04). CMOS gate oxides are easily damaged by electrostatic discharge. Use anti-static packaging, wrist strap, and mat.
Do not short the output pin of any gate to VCC or GND while the IC is powered. Most 7400-series outputs have limited short-circuit current tolerance and will overheat or fail.

Tools needed

Digital multimeter with DC voltage and continuity functions
5 V regulated DC power supply
Solderless breadboard or PCB
Logic probe or oscilloscope
Anti-static wrist strap and mat (for CMOS variants)
Tweezers and IC extraction tool (for DIP socket use)

Common mistakes

Swapping pin 7 (GND) and pin 14 (VCC) by inserting the IC into the circuit backwards — a 180° rotation that reverses all pin assignments and instantly destroys the device.
Leaving unused CMOS inputs floating, causing the gate to oscillate and the IC to draw excessive supply current.
Mixing TTL output drive (74LS04 output) with a 74HC04 input whose VIH threshold differs from TTL levels — the 74HCT04 exists precisely to solve this interface problem.
Omitting the VCC decoupling capacitor, causing supply-rail glitches that produce spurious logic transitions on all six gate outputs.
Connecting a gate output directly to VCC or GND without a current-limiting resistor, expecting it to act as a switch — the output is a push-pull driver with limited short-circuit tolerance.

Troubleshooting

IC output is always LOW regardless of input state: Cause: VCC not connected to pin 14, or IC inserted backwards (pin 1 and pin 14 swapped). Fix: Power down. Verify pin 14 is on the VCC rail and pin 7 is on GND with a multimeter. If the IC was inserted backwards, replace it — the original IC is likely damaged.
IC gets hot immediately after power-on: Cause: IC inserted backwards (VCC and GND reversed), or output shorted to supply rail. Fix: Power down immediately. Check IC orientation. Verify no wiring shorts from output pins to VCC or GND. Replace the IC if it was reverse-powered.
Output oscillates even with a static DC input: Cause: Floating input on a CMOS variant (74HC04), or power supply noise coupling into an unterminated input. Fix: Tie all unused inputs to VCC or GND. Add 100 nF decoupling capacitor between pin 14 and pin 7. Verify the input signal source has a defined source impedance or pull-up/pull-down.

Frequently asked questions

What does the 7404 IC do?

The 7404 contains six independent logic inverters (NOT gates). Each gate takes one digital input and produces the logical complement at its output: a HIGH input (logic 1) becomes a LOW output (logic 0), and a LOW input becomes a HIGH output. It is used for signal inversion, level shifting, oscillator circuits, and driving complementary logic signals.

What are pin 7 and pin 14 on the 7404?

Pin 7 is the GND (ground) connection — the 0 V reference for all six gates. Pin 14 is VCC, the positive power supply. For a 74LS04 this is 5 V ±5%. For a 74HC04 it is 2 V to 6 V. Always connect a 100 nF decoupling capacitor between VCC and GND as close to pin 14 and pin 7 as possible.

What is the difference between the 7404, 74LS04, 74HC04, and 74HCT04?

All four are hex inverters with identical pinouts. They differ in technology family: 7404 is original bipolar TTL (5 V, higher power). 74LS04 is Low-power Schottky TTL (5 V, lower power). 74HC04 is High-speed CMOS (2–6 V, very low power). 74HCT04 is CMOS with TTL-compatible input thresholds (5 V, for TTL interfacing). Choose the family matching your supply voltage and interfacing requirements.

Can I leave unused 7404 inverter inputs unconnected?

No. Floating CMOS inputs (74HC04, 74HCT04) will oscillate, causing excessive power consumption and EMI. Floating TTL inputs (7404, 74LS04) default high due to internal pull-ups but are unreliable in noisy environments. Tie all unused inputs to VCC or GND depending on whether a logic HIGH or LOW is needed. Unused outputs can be left unconnected.

What is a typical use case for a hex inverter IC?

Common uses include: inverting a clock signal to create a complementary clock, generating enable/disable signals that are the logical opposite of an existing control line, buffering weak signals by driving a hex inverter's output (which has a defined drive strength), creating a Schmitt-trigger oscillator when the 74HC04 (which has internal Schmitt inputs on some variants) is used with an RC network.