A method includes providing an oscillator having a field effect transistor connected with a resonant circuit. The field effect transistor has a gate electrode coupled to a source of gate voltage, a source electrode, a drain electrode and a graphene channel disposed between the source electrode and the drain electrode and electrically connected thereto. The method further includes biasing the graphene channel via the gate electrode into a negative differential resistance region of operation to cause the oscillator to generate a frequency signal having a resonant frequency f0. There can be an additional step of varying the gate voltage so as to bias the graphene channel into the negative differential resistance region of operation and out of the negative differential resistance region of operation so as to turn on the frequency signal and to turn off the frequency signal, respectively.