Schmitt trigger circuit LM324
In this project, we're going to see how the operational amplifier works when used as a Schmitt trigger circuit and a comparator. Figure shows that the Schmitt trigger circuit provides different hysteresis loops as you turn the control volume clockwise or counterclockwise.
Now, let get to the experiment. Turn power ON while leaving S1 OFF, and the operational amplifier works as a comparator. When you rotate the control volume, LEDs 1 and 2 take turns lighting at some point. Note that this point doesn't change whether you turn the control volume clockwise or counterclockwise.
Now, press S1 ON, and you'll have a Schmitt trigger circuit that produces hysteresis loops, as shown in Figure 1. The width of hysteresis becomes narrower as the RB/ RA ratio increases. Notice how the width changes when by using different value for RA and RB.