Patent ID: 6906524
Filing Date: 2005-06-14
Classification: G01N

Abstract:
1. An electronic circuit for ion sensor, comprising: a bridge sensing circuit comprising an input terminal and a sensing output terminal, for sensing ion concentration of a solution, wherein the bridge sensing circuit comprises an ion sensing element, which has a reference electrode coupled to a ground, and one terminal of which coupled to the sensing output terminal for delivering the signal of ion concentration; and a differential amplifying circuit, where a reference voltage is inputted into one input terminal of the differential amplifying circuit, while the other input terminal is coupled to the sensing output terminal of the bridge sensing circuit for delivering a differential voltage to the input terminal of the bridge sensing circuit such that the ion sensing element senses the ion concentration under the conditions of constant current and constant voltage; wherein the bridge sensing circuit further comprises: a first amplifier; a first impedance element, coupled between the input terminal of the bridge sensing circuit and the positive terminal of the first amplifier; a second impedance element, coupled between the positive terminal and the output terminal of the first amplifier; a third impedance element, coupled to the input terminal of the bridge sensing circuit and the negative terminal of the first amplifier thereby determining the constant current; wherein the first amplifier, the first impedance element, the second impedance element, the third impedance element, and the ion sensing element constitute a bridge network such that the ion sensing element operates under the conditions of constant drain-source voltage and constant drain current; and wherein the ion sensing element is an ISFET, whose drain terminal is coupled to the negative terminal of the first amplifier, the source terminal is coupled to the output terminal of the first amplifier, and the reference electrode is coupled to a ground.