RC Low-Pass Filter Step Response

Watch a square wave bend into an exponential curve through a single resistor and capacitor.

Difficulty: Breadboard. Estimated build time: about 20 minutes. Estimated parts cost: about US$0.75. 4-part bill of materials with live supplier pricing. A teaching circuit that exists for one purpose: to make the famous V_out = V_in × (1 − e^(−t/RC)) curve visible on an oscilloscope.