Differential amplifier LM324
Now, we're going to construct a differential amplifier using the op amplifier.
In this experiment, we'll provide input to both the + and - terminals of the op amplifier. The differential amplifier amplifies the difference between these two inputs. If the two inputs are the same, it produces no output at all.
Let's get to the experiment. Use the signal output from the phase-shifting CR oscillator. Turn power ON, and you'll hear a high-pitched sound produced by the speaker. Can you guess why?
Yes, it's because S1 is still OFF at this time and the op amplifier is working as an inverting amplifier. Now, see what happens by pressing S1. You'll notice the sound from the speaker is toned down or becomes almost inaudible. This is the function of the differential amplifier. Using this function, we can suppress noise and amplify only the signal we want to listen.