HEF4093BT Quad 2-Input NAND Schmitt Trigger: Datasheet, Pinout, and Application Circuits
The HEF4093BT is a monolithic integrated circuit fabricated in Metal Oxide Semiconductor (MOS) technology. It belongs to the 4000 series of CMOS logic chips, renowned for their low power consumption and wide operating voltage range. This device contains four independent 2-input NAND gates, each featuring Schmitt-trigger action on their inputs. This unique combination makes it far more versatile than a standard NAND gate, serving not only as a logic gate but also as a highly effective oscillator, pulse shaper, and noise eliminator.
Datasheet Overview and Key Specifications
The HEF4093BT is characterized by its wide supply voltage range, typically from 3V to 15V, making it compatible with various logic levels and perfect for battery-powered applications. Its high noise immunity is a hallmark of CMOS technology and is further enhanced by the Schmitt-trigger inputs.
Key absolute maximum ratings and electrical characteristics include:
Supply Voltage Range (VDD): -0.5V to +18V
Input Voltage Range (Vin): -0.5V to VDD + 0.5V
Operating Temperature Range: -40°C to +125°C
Low Power Consumption: Quiescent current of just a few microamps (typ. at 5V)
High Noise Immunity: Typically 0.45 VDD
The Schmitt-trigger functionality means each input has a different voltage threshold for a low-to-high transition (VT+) versus a high-to-low transition (VT-). This difference, known as the hysteresis voltage (ΔV), is typically around 0.9V at 5V VDD. This hysteresis is the key feature that allows the chip to clean up noisy signals and create stable oscillations.
Pinout Configuration
The HEF4093BT is packaged in a standard 14-pin DIP (Dual In-line Package) or SOIC (Small Outline Integrated Circuit). The pinout is as follows:
Pin 1: Input 1A (Gate 1, Input A)
Pin 2: Input 1B (Gate 1, Input B)
Pin 3: Output 1Y (Gate 1, Output)
Pin 4: Output 2Y (Gate 2, Output)
Pin 5: Input 2B (Gate 2, Input B)
Pin 6: Input 2A (Gate 2, Input A)
Pin 7: VSS (Ground)
Pin 8: Input 3A (Gate 3, Input A)
Pin 9: Input 3B (Gate 3, Input B)
Pin 10: Output 3Y (Gate 3, Output)
Pin 11: Output 4Y (Gate 4, Output)
Pin 12: Input 4B (Gate 4, Input B)
Pin 13: Input 4A (Gate 4, Input A)
Pin 14: VDD (Positive Supply Voltage)
Application Circuits
The built-in hysteresis of the HEF4093BT opens the door to several practical applications beyond simple logic operations.
1. Schmitt Trigger (Signal Conditioning):
The most straightforward use is to convert a slow or noisy input signal into a clean, sharp digital output. Simply connect the noisy signal to one input of a NAND gate and tie the other input to a logic HIGH (VDD). The output will be a crisp, jitter-free square wave, as the hysteresis prevents multiple transitions when the input signal lingers near the threshold voltage.
2. Astable Multivibrator (Oscillator):
A single gate from the HEF4093BT can be configured as a simple square wave oscillator. This is achieved by connecting a resistor (R) between the output and input and a capacitor (C) from the input to ground. The Schmitt-trigger action is essential for this circuit to work reliably, as it provides a predictable charge and discharge cycle for the capacitor. The oscillation frequency is determined by the formula f ≈ 1 / (1.2 R C). This circuit is perfect for generating clock pulses, tone signals, or blinking LEDs.
3. Monostable Multivibrator (Pulse Generator):
By using two gates from the IC, you can create a monostable or one-shot pulse generator. This circuit produces a single output pulse of a fixed duration in response to a trigger signal on the input. The pulse width is determined by an external resistor and capacitor (RC network). This is useful for creating timed delays or debouncing mechanical switches.
4. Touch Switch:
The high input impedance of CMOS gates allows the HEF4093BT to be used in sensitive touch-activated circuits. A touch plate connected to the Schmitt-trigger input can couple enough mains hum or body capacitance to trigger the gate, toggling the output. This demonstrates its sensitivity and ability to work with very weak signals.
ICGOODFIND: The HEF4093BT is an exceptionally versatile and robust IC that transcends the role of a simple logic gate. Its integrated Schmitt-trigger inputs make it an indispensable component for signal conditioning, oscillator design, and noise immunity in a wide range of electronic projects, from simple educational kits to complex industrial systems. Its ease of use, low cost, and wide voltage range ensure its continued popularity among engineers and hobbyists alike.
Keywords: Schmitt Trigger, CMOS Logic, Oscillator Circuit, Signal Conditioning, Hysteresis Voltage
