The scenario
A TTP223 capacitive touch sensor IC detects finger contact and drives an NPN transistor to switch an LED night lamp, powered by a 3V battery.
What is in this drawing
Read the decisions behind it.
01
Use a 2N2222 NPN transistor because the TTP223 output cannot directly handle the LED current.
02
Add a 100nF decoupling capacitor across the IC supply to keep touch sensing stable.
03
Model the touch pad as a 10pF capacitor to ground so the net is not left open.
Reuse for any battery-powered capacitive touch lamp or low-power touch-controlled load.
More like this