The design of a CMOS clamped-clamped beam resonator along with a full custom integrated differential amplifier, monolithically fabricated with a commercial 0.35 ${mu}m$ CMOS technology, is presented. The implemented amplifier, which minimizes the negative effect of the parasitic capacitance, enhances the electrical MEMS characterization, obtaining a $48{ imes}10^8$ resonant frequency-quality factor product ($Q{ imes}f_{res}$) in air conditions, which is quite competitive in comparison with existing CMOS-MEMS resonators.