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sn74hct14n-hex-schmitt-trigger

5 min read

Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

SN74HCT14N - Hex Inverting Schmitt Trigger

Details

  • Location: Cabinet-3, Bin 41, Sections A & B
  • Category: Logic ICs
  • Brand: Texas Instruments
  • Part Number: SN74HCT14N
  • Package: 14-DIP
  • Quantity: 41 total (14 + 27)
  • Status: Available
  • Price Range: $0.50-1.00
  • Supplier: Mixed sourcing (see breakdown below)
  • Datasheet: SN74HCT14 Datasheet
  • Product URL: https://www.ti.com/product/SN74HCT14

Sourcing Breakdown

  • Section A: 14 units from Digikey (high reliability, guaranteed authentic)
  • Section B: 27 units from other sources (standard reliability)

Description

The SN74HCT14N contains six independent inverting Schmitt trigger gates. Each gate performs the Boolean function Y = A̅ (NOT A) with Schmitt trigger input characteristics that provide different input threshold voltages for positive-going (VT+) and negative-going (VT-) signals. This hysteresis provides excellent noise immunity and makes the device ideal for signal conditioning applications, switch debouncing, and converting slowly changing input signals into clean digital outputs.

Specifications

Electrical Characteristics

  • Supply Voltage (VCC): 4.5V ~ 5.5V
  • Input Voltage Range: 0V to VCC
  • Output Voltage: 0V to VCC
  • Positive-going Threshold (VT+): 1.6V typical @ VCC = 4.5V
  • Negative-going Threshold (VT-): 0.8V typical @ VCC = 4.5V
  • Hysteresis (VT+ - VT-): 0.8V typical
  • Propagation Delay: 18ns typical
  • Output Drive Current: ±4mA minimum

Physical Characteristics

  • Package: 14-pin DIP (Dual In-line Package)
  • Dimensions: 0.300” (7.62mm) width
  • Pin Pitch: 0.100” (2.54mm)
  • Operating Temperature: -40°C to +85°C

Key Features

  • Six independent inverting Schmitt triggers
  • TTL-compatible inputs and outputs
  • High noise immunity due to hysteresis
  • Excellent for signal conditioning
  • Low power CMOS technology
  • Wide operating voltage range

Pinout Diagram

    SN74HCT14N 14-Pin DIP
    ┌─────────────────┐
1A  │1             14│ VCC
1Y  │2             13│ 6A
2A  │3             12│ 6Y
2Y  │4             11│ 5A
3A  │5             10│ 5Y
3Y  │6              9│ 4A
GND │7              8│ 4Y
    └─────────────────┘

Pin Descriptions

PinNameDescription
11AInput A of gate 1
21YOutput Y of gate 1 (inverted)
32AInput A of gate 2
42YOutput Y of gate 2 (inverted)
53AInput A of gate 3
63YOutput Y of gate 3 (inverted)
7GNDGround
84YOutput Y of gate 4 (inverted)
94AInput A of gate 4
105YOutput Y of gate 5 (inverted)
115AInput A of gate 5
126YOutput Y of gate 6 (inverted)
136AInput A of gate 6
14VCCPower supply (+5V)

Schmitt Trigger Characteristics

Hysteresis Behavior

  • VT+ (Positive Threshold): ~1.6V - Input must exceed this for LOW to HIGH output transition
  • VT- (Negative Threshold): ~0.8V - Input must fall below this for HIGH to LOW output transition
  • Hysteresis Window: ~0.8V - Provides excellent noise immunity
  • Output Inversion: HIGH input produces LOW output, LOW input produces HIGH output

Transfer Characteristics

Input Voltage vs Output Voltage:
- Input < 0.8V → Output = HIGH (VCC)
- Input > 1.6V → Output = LOW (0V)
- 0.8V < Input < 1.6V → Output maintains previous state

Applications

Common use cases for the SN74HCT14N:

  • Switch debouncing circuits
  • Signal conditioning and cleanup
  • Oscillator and timing circuits
  • Waveform shaping and squaring
  • Noise filtering in digital systems
  • Level shifting and signal buffering
  • Crystal oscillator circuits
  • Pulse shaping applications

Circuit Examples

Basic Switch Debouncer

Switch ---- 10kΩ pullup ---- VCC
Switch ---- Input (1A)
Output (1Y) ---- Clean digital signal
0.1µF capacitor from input to ground for additional filtering

Simple Oscillator Circuit

Gate 1: Input (1A) ---- Output (1Y)
Gate 2: Input (2A) ---- Output (2Y) ---- back to 1A
RC timing network: 1Y ---- Resistor ---- 2A ---- Capacitor ---- GND
Frequency ≈ 1/(2.2 × R × C)

Signal Conditioning Chain

Noisy input ---- Gate 1 ---- Gate 2 ---- Clean inverted output
Use two gates in series for non-inverting clean output
Each gate provides additional noise filtering

Crystal Oscillator

Crystal between input and output of one gate
Feedback resistor (1MΩ) in parallel with crystal
Load capacitors on both crystal terminals to ground
Provides stable clock signal generation

Programming Examples

Arduino Interface Example

#define SCHMITT_INPUT 2   // Connect to SN74HCT14N output
#define NOISY_SIGNAL 3    // Connect to SN74HCT14N input
 
void setup() {
  pinMode(SCHMITT_INPUT, INPUT);
  pinMode(NOISY_SIGNAL, OUTPUT);
  Serial.begin(9600);
}
 
void loop() {
  // Read cleaned signal from Schmitt trigger
  int cleanSignal = digitalRead(SCHMITT_INPUT);
  Serial.println(cleanSignal);
  delay(100);
}

Debounced Button Reading

// Hardware: Button -> SN74HCT14N -> Arduino pin
#define BUTTON_PIN 2
 
void setup() {
  pinMode(BUTTON_PIN, INPUT);
  Serial.begin(9600);
}
 
void loop() {
  // Signal is already debounced by Schmitt trigger
  if (digitalRead(BUTTON_PIN) == LOW) {
    Serial.println("Button pressed!");
    delay(200); // Simple software debounce for user feedback
  }
}

Technical Notes

Important considerations for the SN74HCT14N:

  • Hysteresis: The key feature providing noise immunity
  • TTL Compatibility: Can interface directly with TTL and CMOS logic
  • Power Supply: Requires stable 5V supply for proper operation
  • Decoupling: Use 0.1µF capacitor between VCC and GND
  • Input Protection: Inputs are protected but avoid exceeding VCC + 0.5V
  • Output Drive: Can drive multiple TTL/CMOS inputs

Design Calculations

Oscillator Frequency

f ≈ 1/(2.2 × R × C)
Where:
- R is the feedback resistor value
- C is the timing capacitor value
- f is the oscillation frequency

RC Time Constant for Debouncing

τ = R × C
Choose τ > 10ms for effective switch debouncing
Typical values: R = 10kΩ, C = 1µF

Tags

schmitt-trigger, hex-inverter, signal-conditioning, noise-immunity, texas-instruments, digikey-sourced cabinet-3 bin-41 status-available

Notes

The SN74HCT14N is an essential component for any digital electronics collection, providing excellent signal conditioning capabilities with built-in noise immunity. Having 41 total units provides exceptional flexibility for multiple simultaneous projects. The Schmitt trigger hysteresis makes these invaluable for cleaning up noisy signals, debouncing switches, and creating stable oscillators. These ICs are perfect for interfacing between analog and digital domains, converting slowly changing or noisy signals into clean digital levels. The TTL compatibility makes them ideal for both vintage and modern digital systems.

Sourcing Strategy

The collection is strategically organized by source reliability:

  • Section A (Digikey): Use these 14 units for critical applications, production projects, or when guaranteed performance is essential
  • Section B (Other sources): Use these 27 units for prototyping, experimentation, educational projects, or non-critical applications

This dual-sourcing approach provides both high-reliability components for important projects and abundant supply for general experimentation, making it a cornerstone component collection for digital circuit design and troubleshooting.

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