Voltage source is alternative. Here we have 5 VAC supplied by transformer (6 V peak)
Greinacher circuit is composed of several stages (you may add as many stages as you want).
Each stage is composed of 2 condensators and 2 diodes.
Each stage rectifies and multiplicates voltage by 2.
Here are 2 stages. So voltage is multiplicated by 4 (2x2).
Voltages are :
. input 1st stage : 6 VAC (peak)
. output 1st stage : 12 VDC
. output 2nd stage : 24 VDC
