Saturday, August 21, 2010

Square wave oscillator (using Schmitt inverter)

In this page, I introduce the square wave oscillator which used the Schmitt inverter circuit which was made with the CMOS.
The Schmitt inverter circuit has the hysteresis characteristic. The circuit to introduce is the oscillation circuit which used this characteristic.
By the hysteresis characteristic, the voltage which becomes the H level with the input voltage of the inverter rising from 0 V (Voltage that the output becomes 0 V) and the voltage which becomes the L level, descending from +5 V (Voltage that the output becomes +5 V) are different.


When using 74HC14, the rough estimate value of the oscillation frequency can be calculated by the following formula.

f = 1/T = 1/CR

f:The oscillation frequency (Hz)
T:The oscillation period (Second)
C:The capacitor (F)
R:The resistor (ohm) Ref: