DEVICE FOR MEASURING THE CONCENTRATION OF IONS IN SOLUTIONS

摘要

PCT No. PCT/DE93/00690 Sec. 371 Date Apr. 24, 1995 Sec. 102(e) Date Apr. 24, 1995 PCT Filed Aug. 4, 1993 PCT Pub. No. WO94/06005 PCT Pub. Date Mar. 17, 1994A circuit layout for measuring ion concentrations in solutions using ion-sensitive field effect transistors is provided. The circuit layout makes it possible to represent the threshold voltage difference of two ISFETs directly and independently of technological tolerances, operationally caused parameter fluctuations, and ambient influences. The circuit layout includes two measuring or test amplifiers, with in each case two differently or identically sensitive ISFETs and two identical FETs. The ISFETs and FETs are connected in such a manner that at the output of the first measuring amplifier occurs the difference of the mean value of the two ISFET threshold voltages and the FET threshold voltage and at the output of the second measuring amplifier occurs the difference of the two ISFET threshold voltages. The output of the first amplifier is connected to the common reference electrode of the four ISFETs.