Patent ID: 7009184

Claim:
A physical quantity measuring system, comprising: an MOS dosimeter sensor equivalent to a variable voltage source ( 24 ) whose value is E Th , proving a purely capacitive impedance ( 26 ) whose value is C Th , wherein the additional impedance ( 12 ) proves a capacitive impedance C and wherein the following relations are satisfied: I G <I<I 0 V DS <V GSo <V T <0 V GSo <E Th C Th /C>1 where V T , I G , I 0 , V DS , V GSo and I respectively are a threshold voltage of a P channel field effect transistor used as a voltage control means, a gate current of the transistor, a polarization current of the transistor, a drain-source voltage of the transistor, an equilibrium gate-source voltage of the transistor and a current flowing in the sensor; and an amplifying device for said sensor, said amplifying device including: voltage control means ( 22 ) connected to output terminals ( 16 , 20 ) of the sensor to maintain between said terminals a noticeably constant voltage; at least one additional impedance ( 12 ) series connected with the sensor in a polarization circuit between output terminals ( 18 , 20 ) of said device, such that a same current flows into the sensor and into the additional impedance; and polarization means ( 14 ) providing the sensor and the additional impedance with said same current (I).