In this paper, we have proposed a method to discover the signal of single AA which is a significant leap in respect to the other Mass Spectrometry alternatives because it is based on simple FET technology that can transduce the fingerprints from orthogonal properties such as the amphoteric behaviour, the dielectric constant and the length of AAs. We have derived an analytical model using the site-binding method modified to facilitate the recognition of AAs or small polypeptides or to distinguish changes within the sequence, in the form of surface potential, capacitance and current, provided that the target analyte remains within the Debye length. The minima/maxima of the δΨo 2 /δpH 2 and capacitance clarify the signatures of the different amino acids, whereas the pH value corresponds to the zero-crossover of the δΨo 2 /δpH 2 and minima of the capacitance matches the isoelectric point from pH-titration.