<p>An oscillator apparatus comprising: a resonator electrode (11) and a second electrode (12) separated from the resonator electrode by a gap (13) having a size that facilitates electron transfer (14) across the gap (13), wherein the resonator electrode (11) is a resonator electrode mounted for oscillatory motion (15) relative to the second electrode (12) that results in a size of the gap between the resonator electrode and the second electrode being time variable; a feedback circuit (20) configured to convey an electron transfer signal dependent upon electron transfer (14) across the gap (13) as a feedback signal (21); and a drive electrode (30) adjacent the resonator electrode (11) configured to receive a feedback signal (21) from a feedback circuit configured to provide a time-varying feedback signal dependent upon electron transfer across a gap.</p>
