The present invention relates to a system comprising an electronic apparatus which comprises: —an electronic device comprising: —a gate electrode (G, BE); —a dielectric (D) arranged over the gate electrode (G, BE); and —a charge sensing structure (CE) with a 2-dimensional charge sensing layer to provide a gate capacitance (Cg) between the charge sensing structure (CE) and the gate electrode structure (G, BE) and a quantum capacitance (Cq) resulting in a total capacitance (Ctot); —a voltage detector to detect an output voltage (Vo) stored in the total capacitance (Ctot). The system further comprises means to apply a gate voltage (Vg) to the gate electrode structure (G, BE) selected to: —make the device operate around most sensitive point of fermi level of the charge sensing structure (CE); and —tune the quantum capacitance (Cq). The present invention also relates to an electronic apparatus adapted to allow the tuning of its quantum capacitance.