Temperature influence on pH-ISFET sensor operating in weak and moderate inversion regime: Model and circuitry

Abstract

a b s t r a c tUsually most pH-ISFET readout circuits, with temperature compensation, were designed using transistors operating in strong regime. However, a classes of circuits elaborated with respect to MOS weak inversion are also very suitable for low-voltage and low-power applications. In this work, we discuss the problem of temperature variation at the sensor and circuit level. An analysis was made of the sensor operating in weak and moderate inversion regime. It has been shown that a simplified version of the EKV model combined with site-binding model can describe the behavior of ISFET toward the temperature and pH change. The experimental results agree very well with the analytical model for devices in large intervals of pH and temperature. Finally, the usage of model development is considered with an original concept of a readout circuit. The result of the simulation shows that the output signal is linear with pH, the design technique permits improving temperature insensitivity. The proposed circuit can be integrated with an ISFET by standard CMOS technology.

Modeling and simulation of temperature drift for ISFET‐based pH sensor and its compensation through machine learning techniques

“…The electrode potential of reference electrode is reported as‐ where E abs (H + /H 2 ) is the normalized hydrogen potential and E ref (Ag/AgCl) is the relative potential of reference electrode. These two potentials are temperature‐independent and their values have been reported in literature as 4.7 and 0.205 V, respectively . The experimentally observed value of the temperature coefficient is 140 μ V/K .…”

“…These two potentials are temperature-independent and their values have been reported in literature as 4.7 and 0.205 V, respectively. 34,35 The experimentally observed value of the temperature coefficient is 140 V/K. 36 Experimentally reported values of hydrogen electrode potential are 4.73 V by Gomer and Tryson, 37 4.7 V by Hansen and Kolb, 38 and 4.74 V by Bousse.…”

Effects of Measurements Conditions on an Extended-Gate FET used as pH sensor

“…The surface potential (ψ) between the sensitive layer and the electrolyte interface depends on the PZC according to the site-binding model 38 :…”

Temperature Compensation Circuit for ISFET Sensor

“…Therefore, several researchers [3][4][5][6][7] have proposed various temperature compensation systems such as the proper choice of a biasing current for a thermal working point to reduce the ISFET's temperature dependency [4]. Hence, the use of a junction diode Zener [4] for temperature compensation on a single ISFET sensor, the employment of an ISFET with a differential configuration (use of a differential amplifier) [8] that increases the immunity against temperature variation, or the combination of attenuators and a differential amplifier alongside with Caprio's quad [7] were used in order to enhance the temperature stability. The trend of the recent works is set on ISFET sensor arrays [9][10][11][12][13], but most of these researches are focused on the wearable and thermoelectrically powered system [11] and on achieving very high accuracy and a small settling time [10].…”

“…In this work, we present a new circuit based on differential measurement (ISFET/ReFET) However, this type of sensor is strongly affected by the temperature variation. Therefore, several researchers [3][4][5][6][7] have proposed various temperature compensation systems such as the proper choice of a biasing current for a thermal working point to reduce the ISFET's temperature dependency [4]. Hence, the use of a junction diode Zener [4] for temperature compensation on a single ISFET sensor, the employment of an ISFET with a differential configuration (use of a differential amplifier) [8] that increases the immunity against temperature variation, or the combination of attenuators and a differential amplifier alongside with Caprio's quad [7] were used in order to enhance the temperature stability.…”