Timer and amplifier

This is a frequency divider using the 555 timer in monostable mode, more appropriately the 555 is operating as a nonretriggerable multivibrator. Once a nonretriggerable multivibrator responds to a trigger, subsequent triggers while the output is active will be ignored. This results to an output frequency being lower than the input frequency. By setting the monostable period to a little less than n times the period of the input, division by n results. To achieve the correct outcome, the output pulse should terminate at the nth high state of the input. Thus, the period of the monostable multivibrator should be between (n x Tin - Thin) to (n x Tin) where Tin is the period of the input and Thin is the input high state time interval. This circuit demonstrates frequency division by 5, the input is a square wave signal with a period of 200 us, 5 cycles will take 1 ms. The period of the 555 output should be between 900 us and 1 ms. Using the standard resistor and capacitor values of 18 kOhms and 0.047 uF, the period is 929.426 us. Note: I just need a square wave input signal that starts at a low state, but the clock signal cannot be configured like this so I used a sine wave feeding an inverting zero crossing detector. I wanted a square wave that starts at low state so that in Simulation settings I can set Initial conditions to "Determine automatically" instead of "User defined". This way the simulation results can be graphed faster. The original circuit where the simulation graphs slowly is in 555 Frequency Divider.