(Or roughly: $f \approx \frac1.2RC$)
The 74HC14 is a popular hex inverter Schmitt trigger IC, and it's commonly used to build simple oscillators. Here's a full story on how to calculate the oscillator frequency using a 74HC14:
because the threshold voltages do not scale perfectly linearly with supply voltage. 74hc14 oscillator calculator full
Suppose we want to design an oscillator with a frequency of 10 kHz, using a 5V supply voltage. We choose a resistor value of 10 kΩ and a capacitor value of 100 nF.
The frequency ( ) of a relaxation oscillator built with a Hex Schmitt-trigger inverter depends on the values of the external resistor ( ) and capacitor ( (Or roughly: $f \approx \frac1
Before the internet had powerful interactive calculators, electronic engineers relied on data tables in datasheets. The from March 2008 provided an elegant solution: a table of numerator values you could use to find the required RC time constant for a specific frequency across various supply voltages. The formula is:
– Useful for hobbyist quick estimates, but not for precision timing. We choose a resistor value of 10 kΩ
The duty cycle of the output square wave depends on how symmetrical the charge and discharge times are. These times are set by the upper (VT+) and lower (VT-) threshold voltages. For the 74HC14, these thresholds are often not centered perfectly, so a true 50% duty cycle is not guaranteed unless the thresholds are exactly at ⅓ and ⅔ VCC. The calculator can handle asymmetrical thresholds as well, giving you accurate duty cycle information.