This paper reports on the development of a MOSFET-based amplifier for the electrical characterisation of chemical field effect capacitors (ChemFEC). Experimental demonstration is performed through the study of SiO2/Si3N4 ion sensitive field effect capacitor (ISFEC) sensors for pH measurement. The amplifications properties are studied according to the ISFEC and MOSFET electrical characteristics. Thus, the ISFEC transition from the accumulation to the inversion regime is shown to be responsible for a non-linear phenomenom. Nevertheless, thanks to a compromise between the ISFEC flat band voltage and the MOSFET threshold voltage, linear responses and high detection sensitivities are evidenced on the [2-12] pH range.