A method of operating an oscillator circuit comprising a resonator is provided. The method comprises maintaining a resonance of the resonator by a) connecting the resonator to an input voltage (Vbuf) for a first pulse period to charge the resonator only partially towards the input voltage (Vbuf); b) connecting the resonator to a second, lower, voltage for a second pulse period to discharge the resonator at least partially; and repeating steps a) and b) at a rate corresponding to the resonance of the resonator and with a phase corresponding to the resonance of the resonator, so as to maintain the resonance of the resonator.