This circuit can produce interesting voltages across capacitor C₂.

The conditions that have to prevail include the following.

• The input voltage source, V_in, takes on positive and negative values.
• Typically, the voltage source would be a sinusoidal source.
• The input voltage source, V_in, is ungrounded.
• Typically, the voltage source would be the output of a transformer.
• Using an ungrounded source means that you can then ground any point in the circuit.
• The output is taken across the second capacitor.
• It is claimed that the output voltage (DC) can be larger than the peak input voltage.  That is left for an interested student to prove.
• You will need good diodes that don't have much reverse current, and good capacitors with low leakage.