A charge pump circuit comprising: an input terminal for receiving an input voltage; first and second flying capacitor terminals for connection, in use, to a flying capacitor; a common terminal; first and second output terminals, said first and second output terminals being coupled, in use, to said common terminal via first and second reservoir capacitors respectively; a switch network for interconnecting said input terminal, said first and second flying capacitor terminals, said common terminal and said first and second output terminals; and a controller for operating said switch network, characterised in that: said controller is operable in a first mode with a single flying capacitor connected to said first and second flying capacitor terminals to operate said switch network in a sequence of states having a first state and a second state to generate at said output terminals a first positive output voltage and a first negative output voltage that are each equal in magnitude to half the magnitude of said input voltage, wherein the switch network is operable in the first state to divide said input voltage between the single flying capacitor and the first reservoir capacitor in series and operable in the second state to apply the single flying capacitor's portion of said divided voltage across the second reservoir capacitor; said controller also being operable in a second mode to operate said switch network in a sequence of states to generate at said output terminals a second positive output voltage and a second negative output voltage that are each equal in magnitude to the magnitude of said input voltage, wherein the switch network is operable in the second mode in a state to charge the flying capacitor and first reservoir capacitor to said input voltage and a state to transfer the voltage from the flying capacitor to the second reservoir capacitor. an input terminal for receiving an input voltage; first and second flying capacitor terminals for connection, in use, to a flying capacitor; a common terminal; first and second output terminals, said first and second output terminals being coupled, in use, to said common terminal via first and second reservoir capacitors respectively; a switch network for interconnecting said input terminal, said first and second flying capacitor terminals, said common terminal and said first and second output terminals; and a controller for operating said switch network, characterised in that: said controller is operable in a first mode with a single flying capacitor connected to said first and second flying capacitor terminals to operate said switch network in a sequence of states having a first state and a second state to generate at said output terminals a first positive output voltage and a first negative output voltage that are each equal in magnitude to half the magnitude of said input voltage, wherein the switch network is operable in the first state to divide said input voltage between the single flying capacitor and the first reservoir capacitor in series and operable in the second state to apply the single flying capacitor's portion of said divided voltage across the second reservoir capacitor; said controller also being operable in a second mode to operate said switch network in a sequence of states to generate at said output terminals a second positive output voltage and a second negative output voltage that are each equal in magnitude to the magnitude of said input voltage, wherein the switch network is operable in the second mode in a state to charge the flying capacitor and first reservoir capacitor to said input voltage and a state to transfer the voltage from the flying capacitor to the second reservoir capacitor. said controller is operable in a first mode with a single flying capacitor connected to said first and second flying capacitor terminals to operate said switch network in a sequence of states having a first state and a second state to generate at said output terminals a first positive output voltage and a first negative output voltage that are each equal in magnitude to half the magnitude of said input voltage, wherein the switch network is operable in the first state to divide said input voltage between the single flying capacitor and the first reservoir capacitor in series and operable in the second state to apply the single flying capacitor's portion of said divided voltage across the second reservoir capacitor; said controller also being operable in a second mode to operate said switch network in a sequence of states to generate at said output terminals a second positive output voltage and a second negative output voltage that are each equal in magnitude to the magnitude of said input voltage, wherein the switch network is operable in the second mode in a state to charge the flying capacitor and first reservoir capacitor to said input voltage and a state to transfer the voltage from the flying capacitor to the second reservoir capacitor.