This is a Simple Voltage Doubler to boost 3V battery voltage to power some low-power 5V circuits. In needs a Clock input with high fan-out. You can use the 74HCT540 in parallel. Work with the Audio frequency range and see.
If you feed a Low Impedance Square wave, like output of 555, which has adequate Source-Sink Punch. to Input A, then it is quite possible you get double the voltage at B on No load.
Mains Voltage Current LED Indicators
There are many designs you can do with just resistors, capacitors, diodes and LEDs. Zeners and Inductors will add to the fun. The Transistor or Zener can make the circuit smart.