In this experiment we will “abuse” our Schmitt trigger to make an ultra fast oscillator.
By choosing the correct values in our circuit, the Schmitt trigger is set up at the edge of it’s switching.
In fact, we created a “wider” gap between the on & off states of the Schmitt trigger so it will perform better as oscillator.
By turning the potentiometer, the switching times between on & off can be adjusted.
This will cause the lamp to adjust it’s brightness.
The Lectron set makes experimenting fun and always challenging.
I like to take classic circuits (like the Schmitt trigger) and create something completely new around this !
Has anyone figured yet out how the oscillations occur ?
Well here’s some explanation :
First, the capacitor starts to charge via R2 and P1.
As soon as the level of the Schmitt trigger is reached, the output of T2 goes HIGH (negative voltage – PNP transistors !) and thus driving T3 to make the lamp go on.
As T2 blocks, the voltage across R7 drops.
This causes the E of T1 going more positive (PNP transistors !). The gain of T1 rises and this is speeding up the process of the Schmitt trigger.
But now, the capacitor will discharge through the B-E junction of T1 and R7 quite rapidly.
This causes the Schmitt trigger to return to start position.