illustrate
These devices are precision timing circuits capable of producing precise time delays or oscillations. In time delay or monostable mode operation, the time interval is determined by an external resistor and capacitor network. In unsteady mode operation, the frequency and duty cycle independently control two external resistors and one external capacitor.
The threshold and trigger levels are generally two-thirds and one-third, respectively, V CCtarget。 These levels can change the end use of the control voltage. When the trigger input falls below the trigger level, the trigger is set and the output goes high. If the trigger input is above the trigger level and the threshold input is above the threshold level, the trigger is reset and the output is low.