Overview

The 74HC14 (SN74HC14) is a hex Schmitt-trigger inverter IC manufactured using high-speed silicon-gate CMOS technology. Containing six independent inverters in a 14-pin package, it performs the Boolean inverting function Y=A‾Y = \overline{A}.

Each input features built-in Schmitt-trigger action, providing input hysteresis (∼0.7V\sim 0.7\text{V} typical at 5V5\text{V}). This allows slow or noisy input signals (such as noisy sensor lines, switch contacts, or sine waves) to be transformed into sharp, clean, jitter-free digital logic signals without false triggering.

Operating from a wide supply voltage range of 2.0V to 6.0V DC, the 74HC14 is widely used for debouncing mechanical switches, RC oscillators, wave shaping, and signal conditioning.

Quick reference

Supply Voltage (VCC)2.0 V to 6.0 V DC
Logic FamilyHigh-Speed CMOS (74HC) / TTL Compatible (74HCT)
Independent Channels6 (Hex Schmitt-Trigger Inverter)
Input Hysteresis (ΔVT\Delta V_T)0.7 V0.7\text{ V} typical at VCC=4.5VVCC = 4.5\text{V}
Propagation Delay12 ns12\text{ ns} typical at VCC=4.5VVCC = 4.5\text{V}
Output Drive Current±5.2 mA\pm 5.2\text{ mA} at VCC=4.5VVCC = 4.5\text{V}
Package14-pin DIP / SOIC-14 / TSSOP-14

Pinout (DIP-14 Package)

text
             ┌───┴───┐
          1A 1│ 1   14│ VCC
          1Y 2│       │13 6A
          2A 3│       │12 6Y
          2Y 4│ 74HC14│11 5A
          3A 5│       │10 5Y
          3Y 6│       │9  4A
         GND 7│       │8  4Y
             └───────┘
PinNameDescription
11AInverter 1 Input (Schmitt Trigger)
21YInverter 1 Output (1Y=1A‾1Y = \overline{1A})
32AInverter 2 Input (Schmitt Trigger)
42YInverter 2 Output (2Y=2A‾2Y = \overline{2A})
53AInverter 3 Input (Schmitt Trigger)
63YInverter 3 Output (3Y=3A‾3Y = \overline{3A})
7GNDGround reference (0 V)
84YInverter 4 Output (4Y=4A‾4Y = \overline{4A})
94AInverter 4 Input (Schmitt Trigger)
105YInverter 5 Output (5Y=5A‾5Y = \overline{5A})
115AInverter 5 Input (Schmitt Trigger)
126YInverter 6 Output (6Y=6A‾6Y = \overline{6A})
136AInverter 6 Input (Schmitt Trigger)
14VCCPower supply voltage (+2.0V to +6.0V DC)

Function & Truth Table (Per Gate)

Input AOutput Y
Low (LL)High (HH)
High (HH)Low (LL)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVCCV_{CC}2.05.06.0VDC
Positive-Going ThresholdVT+V_{T+}2.02.53.15VVCC=4.5VV_{CC} = 4.5\text{V}
Negative-Going ThresholdVT−V_{T-}0.91.82.4VVCC=4.5VV_{CC} = 4.5\text{V}
Hysteresis VoltageΔVT\Delta V_T0.40.71.4VVCC=4.5VV_{CC} = 4.5\text{V}
Propagation Delay (A→YA \rightarrow Y)tPDt_{PD}—1221nsVCC=4.5V,CL=50pFV_{CC} = 4.5\text{V}, C_L = 50\text{pF}
Output Drive CurrentIOUTI_{OUT}——±5.2\pm 5.2mAVCC=4.5VV_{CC} = 4.5\text{V}
Quiescent Supply CurrentICCI_{CC}——2.0µAVIN=VCC or GNDV_{IN} = V_{CC}\text{ or GND}

Typical Applications

Simple RC Oscillator / Clock Generator

A single inverter channel configured with a feedback resistor RR and input capacitor CC forms a simple relaxation oscillator.

text
       ┌─────────── R (10k) ──────────┐
       │                              │
       │     ┌───┐                    │
  ─────┴────┤o   ├─── Output Clock ───┴─────
       │     └───┘
     ═══ C (10nF)
       │
      GND

Common mistakes

  • Leaving inputs of unused inverters floating: Unused CMOS inputs (e.g. pins 5, 9, 11, 13) must be connected to VCCV_{CC} or GND. Floating inputs drift into the linear threshold region, causing thermal drift, high power consumption, and oscillation noise.
  • Driving 74HC14 with 3.3V signals when powered from 5V: When powered from 5V5\text{V}, VT+V_{T+} can be up to 3.15V3.15\text{V}. A 3.3V logic high signal may barely exceed VT+V_{T+}. Use the 74HCT14 variant for 3.3V TTL-compatible input switching.

Notes

  • 74HC14 vs 74HC04: 74HC04 contains standard hex inverters without Schmitt-trigger hysteresis; 74HC14 adds hysteresis on every input channel.

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