WO2009088278A2 - Temperature compensation method for ion sensor using vt extractor circuit - Google Patents

Temperature compensation method for ion sensor using vt extractor circuit Download PDF

Info

Publication number
WO2009088278A2
WO2009088278A2 PCT/MY2008/000193 MY2008000193W WO2009088278A2 WO 2009088278 A2 WO2009088278 A2 WO 2009088278A2 MY 2008000193 W MY2008000193 W MY 2008000193W WO 2009088278 A2 WO2009088278 A2 WO 2009088278A2
Authority
WO
WIPO (PCT)
Prior art keywords
circuit
isfet
sensor
temperature coefficient
temperature
Prior art date
Application number
PCT/MY2008/000193
Other languages
French (fr)
Other versions
WO2009088278A3 (en
Inventor
Yuzman Yusoff
Nabihah Razali
Rohana Musa
Mohamad Faizal Hashim
Original Assignee
Mimos Berhad
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mimos Berhad filed Critical Mimos Berhad
Publication of WO2009088278A2 publication Critical patent/WO2009088278A2/en
Publication of WO2009088278A3 publication Critical patent/WO2009088278A3/en

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
    • H03F1/301—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in MOSFET amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/447—Indexing scheme relating to amplifiers the amplifier being protected to temperature influence
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45138—Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers

Definitions

  • the present invention relates to the adaptable analog read-out interface circuit for hydrogen ion sensors, and more specific for ion-sensitive field effect transistor (ISFET) pH sensor.
  • This interface circuit is invented together with additional CMOS temperature sensor (threshold voltage extraction) in order to improve the ISFET temperature dependence.
  • This invention improves the thermal stability of the ISFET and thus gives a more accurate pH lOmeasurement.
  • ISFET Ion-sensitive field effect transistor
  • ISFET structure is very similar to conventional MOSFET, except for the standard metal gate is replaced by reference electrode and electrolyte.
  • the threshold voltage of ISFET is changed due to the change in concentration of hydrogen ions (expressed by the pH change of the 0electrolyte), so that the voltage response is often used as an output signal of the ISFET.
  • the sensor To capture the electrical signal generated by a sensor, the sensor (ISFET) must be accompanied with an analog read-out interface.
  • the ISFET has problems in reproducibility, stability, drift and temperature dependence. Every improvement in these aspects will undoubtedly increase the usage of ISFET.
  • the invented 5analog read-out circuit provides solution in improving ISFET temperature dependence. BACKGROUND ART
  • This application only uses a resistor temperature sensor. There is no means for adjustment and tuning.
  • This application is without any temperature compensation at all and uses a bridge type technique as ion sensing mechanism.
  • This application uses complementary ISFET-MOSFET pair technique for ion sensing mechanism.
  • This readout circuit is to cancel the positive temperature coefficient of ISFET with the negative temperature coefficient of Vt circuit. Temperature coefficient of both devices 5can be combined through summation circuit and produce nearly zero temperature coefficient. Thus, the ISFET temperature dependence characteristic is improved.
  • the circuit and method consists of 0 i. a constant voltage constant current circuit, ii. tunable CMOS temperature sensor iii. summation circuit with adjustable output voltage level
  • the improvement is achieved by summation of the positive temperature coefficient of the ISFET and the negative coefficient of the CMOS temperature sensor. 5 LIST OF ACCOMPANYING DRAWINGS
  • FIG. 1 Shows the analog read-out interface circuit with temperature compensation as schematic
  • FIG. 10 Shows the Constant Voltage Constant Current (CVCC) circuit as schematic
  • a method and circuit for an analog read-out interface circuit for ion sensor consist of : i. a constant voltage constant current circuit, 0 ii. tunable CMOS temperature sensor iii. summation circuit with adjustable output voltage level
  • Fig.2 shows the proposed analog readout-interface circuit for pH sensor. It consists of three major components: a threshold voltage (Vt) extraction circuit as temperature sensor (1) , constant- voltage-constant-current (CVCC) circuit (2) and a summation circuit (4).
  • Vt threshold voltage
  • CVCC constant- voltage-constant-current
  • Fig.2 shows the proposed analog readout-interface circuit for pH sensor. It consists of three major components: a threshold voltage (Vt) extraction circuit as temperature sensor (1) , constant- voltage-constant-current (CVCC) circuit (2) and a summation circuit (4).
  • Vt threshold voltage
  • CVCC constant- voltage-constant-current
  • the sensing circuit of Fig.3 detects the ion concentration of the solution with features of constant voltage/constant current operation mode, and floating reference electrode.
  • the drainterrninal of the transistor ISFET is connected to the output terminal of the first amplifier OPl (5), where a constant voltage, e.g., 0.95 volts in the figure, is fed to its positive terminal (12).
  • the negative terminal is connected to the output terminal (6).
  • the source terminal of the transistor ISFET is coupled with the negative terminal of the second amplifier OP2 (7), and coupled with the ground via a resistor R.
  • a constant voltage, e.g., 0.75 volts in the figure, is fedto the positive terminal of the second amplifier OP2 (11).
  • the output terminal of the second amplifier OP2 is coupled with the reference electrode Ref of the transistor ISFET (8).
  • Another amplifier OP3 is connected as a buffer (9). With this configuration, two constant voltages input to the two positive terminals of the amplifiers cause the source terminal S (7) and the drain terminal D (5) of the transistor ISFET to keep a constant .drain-source voltage difference. Thesolution of the ion concentration creates the connection between the reference electrode Ref and gate sensing membrane (terminal G) (10). The potential difference between the gate sensing membrane and the reference electrode Ref (8) is determined by the ion concentration of the solution. (B). Temperature sensor based on Vt extractor circuit
  • This temperature sensor uses CMOS circuitry to extract the threshold voltage of an MOS transistor.
  • This three terminal 5 Vt Extractor is designed with the inclusion of self-bias and a differential amplifier. The output is equal to the threshold voltage of one of the transistors used in the design. Thus, the negative temperature coefficient is obtained (sweep temperature).
  • a variable resistor, Rl (13) , and fixed resistor, R2 (14), are used to control the current and temperature coefficient.
  • R2 (14) By adjusting R2 (14) to the right value, the temperature coefficient of lOtemperature sensor can be tuned closely to ISFET temperature coefficient, but its value still negative. It is important to have this option because fabricated ISFET has high possibility to mismatch from expectation.
  • the read-out circuitry is completed by feeding electrical signal generated by both temperature sensor and CVCC circuit into summation circuit that mutually offset their temperature coefficient and produces a temperature independent output signal.
  • Fig. 5 shows circuit configuration of summation circuit. It consists of an operational amplifier and four additional 0resistors. The output voltage level of summation circuit can be adjusted by controlling input voltage of Vref ( 15).
  • This invention is designed at circuit level and simulated using MTMOS 0.35um CMOS technology.
  • the simulated result demonstrates that temperature dependence of ISFET 5improved from 1.42mV/°C to less than 0.2m V/°C over a temperature range of O 0 C to 65 0 C.
  • the complete layout of this analog read-out interface circuit has been sent for fabrication, waiting for the complete chip to come out. According to a preferred embodiment of the present invention, there are the following circuits:

Abstract

An adaptable analog read-out interface circuit for ion-sensitive field effect transistor (ISFET) has been invented that uses a CMOS temperature sensor (threshold voltage extraction) to improve the thermal stability of the ISFET. The improvement is achieved by summation of the positive temperature coefficient of the ISFET and the negative coefficient of the CMOS temperature sensor.

Description

TITLE OF THE INVENTION
Temperature compensation method for ion sensor using Vt extractor circuit.
TECHNICAL FIELD
5The present invention relates to the adaptable analog read-out interface circuit for hydrogen ion sensors, and more specific for ion-sensitive field effect transistor (ISFET) pH sensor. This interface circuit is invented together with additional CMOS temperature sensor (threshold voltage extraction) in order to improve the ISFET temperature dependence. This invention improves the thermal stability of the ISFET and thus gives a more accurate pH lOmeasurement.
BACKGROUND
Advancement in microelectronic and semiconductor technology has enabled new in capabilities in field of sensor development, particularly of pH sensors based on field effect
15transistor. Ion-sensitive field effect transistor (ISFET), a kind of micro-sensing device invented by Bergveld in 1970 and developed quickly thereafter.
ISFET structure is very similar to conventional MOSFET, except for the standard metal gate is replaced by reference electrode and electrolyte. The threshold voltage of ISFET is changed due to the change in concentration of hydrogen ions (expressed by the pH change of the 0electrolyte), so that the voltage response is often used as an output signal of the ISFET. To capture the electrical signal generated by a sensor, the sensor (ISFET) must be accompanied with an analog read-out interface.
The ISFET has problems in reproducibility, stability, drift and temperature dependence. Every improvement in these aspects will undoubtedly increase the usage of ISFET. The invented 5analog read-out circuit provides solution in improving ISFET temperature dependence. BACKGROUND ART
There are three patents that deal with our application area.
US Patent 4879517 5Title: Temperature compensation for potentiometrically operated ISFETs
This application only uses a resistor temperature sensor. There is no means for adjustment and tuning.
US Patent 6906524 lOTitle: Electronic circuit for ion sensor
This application is without any temperature compensation at all and uses a bridge type technique as ion sensing mechanism.
15US Patent 20070138028 Title: PH-Change sensor and method
This application uses complementary ISFET-MOSFET pair technique for ion sensing mechanism.
20
PRINCIPAL CONCEPT
The principle of this readout circuit is to cancel the positive temperature coefficient of ISFET with the negative temperature coefficient of Vt circuit. Temperature coefficient of both devices 5can be combined through summation circuit and produce nearly zero temperature coefficient. Thus, the ISFET temperature dependence characteristic is improved.
SUMMARY OF DISCLOSURE
The circuit and method consists of 0 i. a constant voltage constant current circuit, ii. tunable CMOS temperature sensor iii. summation circuit with adjustable output voltage level
The improvement is achieved by summation of the positive temperature coefficient of the ISFET and the negative coefficient of the CMOS temperature sensor. 5 LIST OF ACCOMPANYING DRAWINGS
Figure 1
Shows the analog read-out interface circuit with temperature compensation as Block diagram 5
Figure 2 Shows the analog read-out interface circuit with temperature compensation as schematic
Figure 3 10 Shows the Constant Voltage Constant Current (CVCC) circuit as schematic
Figure 4
Shows the Vt Extractor circuit with TC controller as schematic
ISFigure 5 Shows the summation circuit as schematic
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 0In describing the preferred embodiments of the present invention as shown in Figures 1 to 5 specific terminologies shall be used for the sake of clarity in the description.
However, it is to be noted that the present invention is not intended to be limited to the specific terminologies so selected and it is to be understood that each specific terminology shall include all technical equivalents operating in a similar fashion to accomplish a similar objective/ 5purpose.
A method and circuit for an analog read-out interface circuit for ion sensor is invented that consist of : i. a constant voltage constant current circuit, 0 ii. tunable CMOS temperature sensor iii. summation circuit with adjustable output voltage level
Fig.2 shows the proposed analog readout-interface circuit for pH sensor. It consists of three major components: a threshold voltage (Vt) extraction circuit as temperature sensor (1) , constant- voltage-constant-current (CVCC) circuit (2) and a summation circuit (4). The principle of this readout circuit is to cancel the positive temperature coefficient of ISFET (3) with the negative temperature coefficient of Vt circuit. Temperature coefficient of both devices can be combined through summation circuit (4) and produce nearly zero temperature coefficient. Thus, the ISFET temperature dependence characteristic is improved.
(A). CVCC circuit
The sensing circuit of Fig.3 detects the ion concentration of the solution with features of constant voltage/constant current operation mode, and floating reference electrode. The drainterrninal of the transistor ISFET is connected to the output terminal of the first amplifier OPl (5), where a constant voltage, e.g., 0.95 volts in the figure, is fed to its positive terminal (12). The negative terminal is connected to the output terminal (6). The source terminal of the transistor ISFET is coupled with the negative terminal of the second amplifier OP2 (7), and coupled with the ground via a resistor R. A constant voltage, e.g., 0.75 volts in the figure, is fedto the positive terminal of the second amplifier OP2 (11). The output terminal of the second amplifier OP2 is coupled with the reference electrode Ref of the transistor ISFET (8). Another amplifier OP3 is connected as a buffer (9). With this configuration, two constant voltages input to the two positive terminals of the amplifiers cause the source terminal S (7) and the drain terminal D (5) of the transistor ISFET to keep a constant .drain-source voltage difference. Thesolution of the ion concentration creates the connection between the reference electrode Ref and gate sensing membrane (terminal G) (10). The potential difference between the gate sensing membrane and the reference electrode Ref (8) is determined by the ion concentration of the solution. (B). Temperature sensor based on Vt extractor circuit
The circuit configuration of this temperature sensor is shown in Fig. 4. This temperature sensor uses CMOS circuitry to extract the threshold voltage of an MOS transistor. This three terminal 5 Vt Extractor is designed with the inclusion of self-bias and a differential amplifier. The output is equal to the threshold voltage of one of the transistors used in the design. Thus, the negative temperature coefficient is obtained (sweep temperature).
A variable resistor, Rl (13) , and fixed resistor, R2 (14), are used to control the current and temperature coefficient. By adjusting R2 (14) to the right value, the temperature coefficient of lOtemperature sensor can be tuned closely to ISFET temperature coefficient, but its value still negative. It is important to have this option because fabricated ISFET has high possibility to mismatch from expectation.
(C) Summation circuit
15
The read-out circuitry is completed by feeding electrical signal generated by both temperature sensor and CVCC circuit into summation circuit that mutually offset their temperature coefficient and produces a temperature independent output signal. Fig. 5 shows circuit configuration of summation circuit. It consists of an operational amplifier and four additional 0resistors. The output voltage level of summation circuit can be adjusted by controlling input voltage of Vref ( 15).
This invention is designed at circuit level and simulated using MTMOS 0.35um CMOS technology. The simulated result demonstrates that temperature dependence of ISFET 5improved from 1.42mV/°C to less than 0.2m V/°C over a temperature range of O0C to 650C. In addition, the complete layout of this analog read-out interface circuit has been sent for fabrication, waiting for the complete chip to come out. According to a preferred embodiment of the present invention, there are the following circuits:
1. Vt Extractor circuit with TC controller
2. Constant Voltage Constant Current Circuit 3. Summation Circuit

Claims

We hereby claim the following:
1. A method for an adaptable analog read-out interface circuit for ISFET based sensor that improves the temperature dependence of the ISFET comprising the steps of: (1) summation of the positive temperature coefficient of the ISFET and the negative temperature coefficient of a CMOS temperature sensor;
(2) tuning of the drift compensation with a variable resistor
2. An adaptable analog read-out interface circuit for ISFET based sensor comprising a means to tune a drift compensation, a means to provide the drift compensation and a means for the ISFET based sensing.
3. The circuit as claimed in 2, wherein the means to provide the drift compensation delivers a negative temperature coefficient using the negative temperature coefficient of a CMOS temperature sensor.
4. The circuit as claimed in 3, wherein the negative temperature coefficient of the drift compensation means is added to the positive temperature coefficient of the
ISFET and by this compensates the temperature dependant drift of the ISFET
5. The circuit as claimed in 4, wherein the negative temperature coefficient of the CMOS temperature sensor is obtained by extracting the threshold voltage of one of the transistors used in the design.
6. The circuit as claimed in any of claims 2 to 5, whereby the means to tune the drift compensation comprises a variable resistor.
7. The circuit as claimed in any of claims 2 to 6, whereby the means for the ISFET based sensing is used as Ph-sensor.
8. A circuit arrangement for an adaptable analog read-out interface circuit for ISFET based sensor, comprising: a Temperature Sensor arrangement; an ISFET which is connected to a Constant Voltage Constant Current circuit
(CVCC): an OP Amp that connects the Temperature Sensor and the CVCC circuit for summation.
9. The circuit arrangement as claimed in 8, wherein the Temperature Sensor arrangement comprises a Vt Extractor which is connected to the positive input terminal of an OP Amp (OP 1), a variable resistor that is connected to the negative input of the said OP Amp (OP 1) and a fixed resistor that is connected between the output and the negative input of the said OP amp (OP 1) to control a temperature coefficient of the Vt Extractor.
PCT/MY2008/000193 2008-01-04 2008-12-23 Temperature compensation method for ion sensor using vt extractor circuit WO2009088278A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
MYPI20080014 2008-01-04
MYPI20080014A MY154799A (en) 2008-01-04 2008-01-04 Temperature compensation method for ion sensor using vt extractor circuit

Publications (2)

Publication Number Publication Date
WO2009088278A2 true WO2009088278A2 (en) 2009-07-16
WO2009088278A3 WO2009088278A3 (en) 2009-10-29

Family

ID=40853639

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/MY2008/000193 WO2009088278A2 (en) 2008-01-04 2008-12-23 Temperature compensation method for ion sensor using vt extractor circuit

Country Status (2)

Country Link
MY (1) MY154799A (en)
WO (1) WO2009088278A2 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017052251A (en) * 2015-09-11 2017-03-16 王子ホールディングス株式会社 Printing sheet, printing sheet with peeling layer, and decorative sheet
JP2017052252A (en) * 2015-09-11 2017-03-16 王子ホールディングス株式会社 Printing sheet, printing sheet with peeling layer, and decorative sheet
CN110186987A (en) * 2019-06-27 2019-08-30 上海三信仪表厂 A kind of general 25 degree of translation methods of solution pH value

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4879517A (en) * 1988-07-25 1989-11-07 General Signal Corporation Temperature compensation for potentiometrically operated ISFETS
US6525554B2 (en) * 2000-07-20 2003-02-25 National Yunlin University Of Science And Technology Method and apparatus for measuring temperature parameters of an ISFET using hydrogenated amorphous silicon as a sensing film

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4879517A (en) * 1988-07-25 1989-11-07 General Signal Corporation Temperature compensation for potentiometrically operated ISFETS
EP0352537B1 (en) * 1988-07-25 1996-12-18 Honeywell Inc. Temperature compensation for potentiometrically operated isfets
US6525554B2 (en) * 2000-07-20 2003-02-25 National Yunlin University Of Science And Technology Method and apparatus for measuring temperature parameters of an ISFET using hydrogenated amorphous silicon as a sensing film

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017052251A (en) * 2015-09-11 2017-03-16 王子ホールディングス株式会社 Printing sheet, printing sheet with peeling layer, and decorative sheet
JP2017052252A (en) * 2015-09-11 2017-03-16 王子ホールディングス株式会社 Printing sheet, printing sheet with peeling layer, and decorative sheet
CN110186987A (en) * 2019-06-27 2019-08-30 上海三信仪表厂 A kind of general 25 degree of translation methods of solution pH value
CN110186987B (en) * 2019-06-27 2022-03-08 上海三信仪表厂 Universal solution PH value 25 degree conversion method

Also Published As

Publication number Publication date
MY154799A (en) 2015-07-31
WO2009088278A3 (en) 2009-10-29

Similar Documents

Publication Publication Date Title
US8232813B2 (en) Sensor circuits
Chung et al. ISFET interface circuit embedded with noise rejection capability
EP1774306B1 (en) Signal processing circuit comprising ion sensitive field effect transistor and method of monitoring a property of a fluid
US5583462A (en) Method and apparatus for multiplexing devices having long thermal time constants
US6906524B2 (en) Electronic circuit for ion sensor
EP2521909B1 (en) Ultra low-power cmos based bio-sensor circuit
JP4137239B2 (en) ISFET array
Miscourides et al. A 12.8 k current-mode velocity-saturation ISFET array for on-chip real-time DNA detection
Miscourides et al. ISFET arrays in CMOS: A head-to-head comparison between voltage and current mode
CN103472114B (en) Multichannel ion sensitive field effect transistor (ISFET) sensor readout circuit with compensation function
CN103376284B (en) Multi-parameter low-power-consumption current-mode ion sensitive field effect tube array sensor device
WO2009088278A2 (en) Temperature compensation method for ion sensor using vt extractor circuit
US5602467A (en) Circuit for measuring ion concentrations in solutions
JP2021105564A (en) Ion sensor device
CN102175740A (en) Multilayer floating-gate all-solid-state pH value sensor based on standard CMOS (Complementary Metal Oxide Semiconductors) technology
CN113281551B (en) Current detection circuit and method
WO2009088280A2 (en) Adaptable analog read-out interface circuit for isfet based sensor
WO2009070003A2 (en) An analog read out interface circuit for ion sensor
WO2009066984A2 (en) Read-out interface circuit for multiple ions sensing
WO2023279113A1 (en) Differential pmos isfet-based ph sensor
CN106921374A (en) Switched capacitor ISFET signal read circuits and its control method
JP2000187018A (en) Semiconductor ion sensor
Aslanzadeh et al. A differential low-power voltage-clamped ISFET topology for biomedical applications
US20070158190A1 (en) PH meter and sensor thereof
Yang et al. An ISFET interface circuitry for biomedical applications

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08869376

Country of ref document: EP

Kind code of ref document: A2

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 08869376

Country of ref document: EP

Kind code of ref document: A2