CD40106BE

The CD40106BE from Texas Instruments contains six independent Schmitt-trigger inverters. Unlike standard inverters (CD4069), Schmitt-trigger inputs have two distinct threshold voltages: a higher threshold (VT+) for the low-to-high transition and a lower threshold (VT−) for the high-to-low transition. The difference (VT+ − VT−) is the hysteresis, typically 1.8V at VDD=10V. This hysteresis makes the CD40106 immune to noise on slowly-changing input signals: once the output switches, the input must change by the full hysteresis voltage (not just a few millivolts of noise) to cause another output transition. This is essential for squaring up sine waves, triangle waves, and other slowly-rising signals that would cause standard gates to oscillate near the threshold. The CD40106 also has no rise/fall time requirement on its input — signals with unlimited transition times are cleanly converted to sharp square waves. The BE suffix denotes the PDIP-14 package with full temperature range.

Each Schmitt-trigger inverter in the CD40106BE has two switching thresholds. When the input voltage rises from 0V, the output remains HIGH until the input exceeds VT+ (the positive-going threshold, ~5.4V at VDD=10V), at which point the output snaps LOW. When the input falls from VDD, the output remains LOW until the input drops below VT− (the negative-going threshold, ~3.6V at VDD=10V), at which point the output snaps HIGH. The 1.8V hysteresis band between VT− and VT+ means that any noise smaller than 1.8V cannot cause false switching. For debouncing: a mechanical switch connected to the input through a pull-up resistor produces multiple transitions as the contacts bounce; the hysteresis filters these bounces and produces a single clean edge at the output. For RC oscillators: connect the output through a resistor to the input, and a capacitor from input to ground. The capacitor charges through the resistor until it reaches VT+, the output goes LOW, the capacitor discharges until it reaches VT−, the output goes HIGH, and the cycle repeats. Frequency ≈ 1/(0.6 × R × C) at VDD=10V.

CD40106BE uses the PDIP-14 package with hex inverter pinout: VDD at Pin 14, VSS at Pin 7. Six independent Schmitt-trigger inverters: Inv 1 (Pin 1 in, Pin 2 out), Inv 2 (Pin 3 in, Pin 4 out), Inv 3 (Pin 5 in, Pin 6 out), Inv 4 (Pin 9 in, Pin 8 out), Inv 5 (Pin 11 in, Pin 10 out), Inv 6 (Pin 13 in, Pin 12 out). The Schmitt-trigger hysteresis (typ 2V at 5V supply) makes this device ideal for noise rejection on slowly changing signals, switch debouncing, and oscillator circuits. For 74HC equivalent with faster switching, use 74HC14 (same pinout, 2-6V supply). The CD40106B hysteresis is supply-voltage proportional.

• Switch Debounce: Switch → 10kΩ pull-up → input; 100nF cap input to GND; output is clean debounced signal; hysteresis filters bounce
• RC Oscillator: Output → 100kΩ → input; 10nF input to GND; free-running ~1kHz square wave oscillator
• Sine-to-Square: Sine wave input → CD40106 inverter; output is clean square wave with fast edges; hysteresis prevents multi-switching
• Level Detector: Analog voltage → input; output HIGH when input VT+; built-in noise immunity

CD40106 is the CMOS 4000-series hex schmitt-trigger inverter operating over the wide 3-18V supply range. The HEF40106 (NXP) and MC1440106 (onsemi) are direct pin-compatible equivalents. For higher speed at the cost of narrower voltage range, the 74HC14 HC/HCT families offer significantly faster propagation delay and lower power consumption at 2-6V. Surface-mount versions use the BM/M suffix (SOIC); through-hole versions use the BE suffix (DIP).