JP2018136174A - Electrochemical measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical measurement device equipped with a simple circuit configuration using an inverter having a discretionary threshold voltage and suitable for downsizing, cost reduction and an increase in flexibility.SOLUTION: The electrochemical measurement device comprises: an electrochemical cell 2 equipped with at least a reference electrode R and a working electrode W; a reference electrode potential control circuit 1 for supplying, using an interval In1, the threshold voltage Vof the inverter to the reference electrode R of the electrochemical cell; and a front-end circuit 3 for bringing about a current value I received by a working electrode W1 of the electrochemical cell or a voltage value Vreceived by a working electrode W2 as a voltage value to each output terminal of inverters In2, In3. The respective threshold voltages Vof the inverters In1-In3 are equalized, and the inverters used for the front-end circuit form a negative feedback circuit by which the input terminals of the inverters are set to the threshold voltages of the inverters.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrochemical measurement apparatus that can be suitably used for, for example, a biosensor that analyzes a sample electrolyte containing a biological sample by an electrochemical method.

In the medical field in recent years, various methods have been proposed for analyzing sample electrolytes. Among them, for example, biosensors using an enzyme analysis method have excellent measurement sensitivity and prompt results. Since it can be obtained, it is widely used including medical institutions such as hospitals.
This enzyme analysis method can be roughly divided into an optical measurement method and an electrochemical measurement method. As electrochemical measurement devices, there are further proposed a current measurement device that measures the current flowing through the working electrode of the electrochemical cell and a potential measurement device that measures the potential difference generated between the working electrode and the reference electrode.

FIG. 14 illustrates the basic configuration of the electrochemical measuring device, and the reference potential generated by the reference electrode potential control circuit shown by block 1 is supplied to the electrochemical cell 2 filled with the sample electrolyte. . The electrochemical cell 2 is provided with a counter electrode and a working electrode in addition to a reference electrode that receives a potential from the reference electrode potential control circuit 1.
In the case of the current measuring device described above, the current signal received at the working electrode in the electrochemical cell 2 is subjected to current / voltage conversion, impedance conversion and amplification in the front end circuit 3, and an analog / digital conversion circuit. 4 is collected as digital data.
In the case of the above-described potential measuring device, the potential signal of the working electrode with respect to the reference electrode in the electrochemical cell 2 is subjected to impedance conversion / amplification by the front end circuit 3 and is converted into digital data through the analog / digital conversion circuit 4. Collected.

An operational amplifier that generally functions as a differential amplifier is used for the reference electrode potential control circuit 1 and the front end circuit 3 in the conventional electrochemical measurement apparatus.
FIG. 15 shows an example of current measurement in a conventional electrochemical measuring apparatus, and the reference electrode potential control circuit 1 is configured by the operational amplifier Op1, the operational amplifier Op2, and the voltage source E1. The reference electrode R of the electrochemical cell 2 is connected to the non-inverting input terminal of the operational amplifier Op1, and the counter electrode C of the electrochemical cell 2 is connected to the output terminal of the operational amplifier Op2. With this configuration, the potential of the reference electrode R is controlled so as to match the potential of the voltage source E1.

The front-end circuit 3 is configured by the operational amplifier Op3, the working electrode W of the electrochemical cell 2 is connected to the inverting input terminal of the operational amplifier Op3, and the non-inverting input terminal of the operational amplifier Op3 is grounded. With this configuration, the potential of the working electrode W is controlled to coincide with the ground potential.
Then, the value of the current flowing through the working electrode W of the electrochemical cell 2 is voltage-converted by the operational amplifier Op3 constituting the front-end circuit 3 and collected as digital data through the analog / digital conversion circuit 4.
Note that an electrochemical measurement device using current measurement shown in FIG. 15 is disclosed in, for example, Patent Document 1.

On the other hand, FIG. 16 shows an example of potential measurement in a conventional electrochemical measuring device. In this example, the reference electrode potential control circuit 1 is configured by grounding the reference electrode R of the electrochemical cell 2, and the potential difference of the working electrode W with respect to the reference electrode R is an operational amplifier constituting the front end circuit 3. The voltage is amplified by Op4 and collected as digital data through the analog / digital conversion circuit 4.
Note that an electrochemical measurement apparatus based on potential measurement shown in FIG. 16 is disclosed in, for example, Patent Document 2.

JP 2005-531759 gazette JP 2013-66176 A

  By the way, these electrochemical measuring devices can be used to monitor mental stress and the like in addition to monitoring of the human health condition. In this case, for example, if the electrochemical measuring device is mounted on a wearable electronic device that can be used by being attached to a part of the human body, such as a bandage, the range of use can be further broadened. For this purpose, it is desirable that the electrochemical measuring device is small, low cost, and flexible.

However, according to the electrochemical measurement apparatus disclosed in Patent Documents 1 and 2 described above, an operational amplifier that constitutes a differential amplifier is used as the electronic device. According to this, the circuit is relatively complicated, and the size is reduced.・ It is disadvantageous for cost reduction.
As an electronic device, it is effective to use an organic field effect transistor made of an organic semiconductor in order to provide flexibility. However, a differential amplifier made of an organic field effect transistor is currently required a voltage of an operating power supply. However, there are problems such as a high input offset voltage and a low gain.

  Therefore, the problem to be solved by the present invention is to use a single-input inverter having an arbitrary threshold voltage instead of using a differential amplifier in the electronic device described above, and is suitable for downsizing, cost reduction and flexibility. Another object of the present invention is to provide an electrochemical measuring device having a simple circuit configuration.

  An electrochemical measurement apparatus according to the present invention made to achieve the above-described object is provided with at least a reference electrode and a working electrode, and an electrochemical cell in which a sample electrolyte is filled between the reference electrode and the working electrode. A reference electrode potential control circuit for supplying a threshold voltage of the inverter to a reference electrode of the electrochemical cell using an inverter, and at least another inverter different from the inverter, and a working electrode of the electrochemical cell Is provided with a front end circuit that provides a current value or a voltage value received at the output terminal of the inverter as a voltage value. The inverter used for the reference electrode potential control circuit and the inverter used for the front end circuit have respective threshold values. The inverters used in the front end circuit form a negative feedback circuit while the voltages are equalized. In wherein the input terminal of the inverter is set to the threshold voltage of the inverter.

  In this case, an analog / digital conversion circuit for converting the output terminal voltage of the inverter into a digital signal is preferably connected to the front end circuit.

  In a preferred embodiment, the inverter used in the reference electrode potential control circuit forms a negative feedback circuit by connecting the output terminal of the inverter to the input terminal, and the threshold voltage of the inverter generated at the input terminal Is configured to be supplied to the reference electrode.

  In another preferred embodiment, the electrochemical cell further includes a counter electrode, an output terminal of an inverter used in the reference electrode potential control circuit is connected to the counter electrode, and an input terminal of the inverter is A negative feedback circuit is configured by being connected to a reference electrode, and a threshold voltage of an inverter generated at the input terminal is configured to be supplied to the reference electrode.

  Furthermore, in a preferred embodiment of the front end circuit, a negative feedback resistor is provided between the output terminal and the input terminal of the inverter, and the working electrode is connected to the input terminal of the inverter so that a current value generated in the working electrode is obtained. The output terminal of the inverter is provided with a current measurement function that converts the voltage value.

  Furthermore, in another preferred embodiment of the front end circuit, a negative feedback resistor is provided between the output terminal and the input terminal of the inverter, and an input resistance is provided between the working electrode and the inverter input terminal. And a potential measuring function for amplifying a potential difference generated between the working electrode and the inverter input terminal as a voltage value at the output terminal of the inverter.

  In addition, each inverter used in the reference electrode potential control circuit and the front-end circuit is preferably composed of an organic thin film transistor.

According to the electrochemical measurement device according to the invention described above, without using the differential amplifier in an electronic device, by using the inverter, becomes to the inverter operates its threshold voltage V _M as a reference voltage.
Then, in the case of adopting the current measurement function as the front-end circuit, the reference electrode potential and the working electrode potential of the electrochemical cell is made to a state consistent with the threshold voltage V _M of each inverter. In addition, the inverter that functions as a current measurement unit can convert a minute input current received by the working electrode with high sensitivity, and provides an electrochemical measurement device with a detection capability with a wide dynamic range that takes advantage of the characteristics of the inverter. can do.

Potential contrast, when employing the potential measurement functions as the front-end circuit, resulting working electrode potential of the electrochemical cell, the difference between the threshold voltage V _M of the inverter constituting the voltage measurement unit, i.e., the input resistance of the inverter Is amplified and output.
Regardless of whether the current measurement function or the potential measurement function is adopted as the front-end circuit, an electrochemical measurement device suitable for further miniaturization can be obtained at low cost by using an inverter that can be configured with a simpler circuit. Can be realized.

It is the block diagram which showed embodiment of the electrochemical measuring device which concerns on this invention. It is the block diagram which similarly showed other embodiment. It is the block diagram which showed the example which measures the threshold voltage of an inverter. It is the diagram which showed the example of the input / output characteristic and threshold voltage of an inverter. It is the diagram which showed the example of the input-output characteristic of the electric current measurement part in the electrochemical measuring device shown in FIG. It is the diagram which showed the example of the input-output characteristic of the electric potential measurement part in the electrochemical measuring device shown in FIG. It is the connection diagram which showed the example of the inverter by a complementary circuit. It is the schematic diagram which showed the laminated structural example of P channel type organic TFT. It is the schematic diagram which showed the laminated structural example of the N channel type organic TFT. It is the wiring diagram which showed the 1st example of the inverter using only P channel type organic TFT. It is the connection diagram which similarly showed the 2nd example. It is the connection diagram which showed the 3rd example similarly. It is the connection diagram which showed the 4th example similarly. It is the block diagram which showed the basic composition of the electrochemical measuring device. It is the block diagram which showed the example of the electric current measurement part in the conventional electrochemical measuring device. It is the block diagram which showed the example of the electric potential measurement part in the conventional electrochemical measuring device.

Hereinafter, an electrochemical measurement apparatus according to the present invention will be described based on the embodiments shown in the drawings.
FIG. 1 shows an embodiment provided with two front-end circuits, a current measuring unit and a potential measuring unit. That is, the electrochemical cell 2 in this embodiment includes a reference electrode R, a counter electrode C, and two working electrodes W1, W2.
The first working electrode W1 is connected to the front end circuit 3 by the current measuring unit 3A, and the second working electrode W2 is connected to the front end circuit 3 by the potential measuring unit 3B.

Further, the reference electrode potential control circuit 1 includes an inverter In1, an input terminal of the inverter In1 is connected to the reference electrode R, and an output terminal of the inverter In1 is connected to the counter electrode C. That is, the inverter In1, the negative feedback circuit through the reference electrode R and the counter electrode C is formed, therefore, the input terminal voltage of the inverter In1 is fixed to the threshold voltage V _M of the inverter In1. The Thereby the reference electrode electrochemical cell 2 R, so that the threshold voltage V _M of the inverter In1 is applied.
Here, the threshold voltage V _M, as shown in FIG. 4, an inverter input voltage (input voltage indicated on the horizontal axis V), the output voltage (output voltage along the vertical axis V) coincides It indicates the value of the input voltage at the point.

On the other hand, the front end circuit 3 by the current measuring unit 3A is connected to the first working electrode W1 of the electrochemical cell 2 as described above. The current measuring unit 3A includes the inverter In2 and the output terminal of the inverter In2. And a negative feedback resistor R1 connected between the input terminals.
As the inverter In2 used in the current measuring unit 3A, an inverter having substantially the same threshold voltage as that of the inverter In1 used in the reference electrode potential control circuit 1 is used, and the first working electrode W1 is input to the inverter In1. Connected to the terminal. The output terminal of the inverter In2 is connected to the analog / digital converter 4, and digital data is output from the output terminal Out.

Further, a front end circuit 3 by a potential measuring unit 3B is connected to the second working electrode W2 of the electrochemical cell 2, and this potential measuring unit 3B includes an inverter In3, and an output terminal and an input terminal of the inverter In3. A negative feedback resistor R2 connected in between and an input resistor R3 connected to the input terminal of the inverter In3.
The inverter In3 used in the potential measuring unit 3B is an inverter having a threshold voltage substantially equal to that of the inverter In1 used in the reference electrode potential control circuit 1, and the second working electrode W2 is connected to the input resistance. It is connected to the input terminal of the inverter In3 via R3. The output terminal of the inverter In3 is connected to the analog / digital converter 4, and digital data is output from the output terminal Out.

According to the current measuring unit 3A described above, the inverter In2, the negative feedback is applied by resistors R1, the input terminal voltage of the inverter In2 is fixed to the threshold voltage V _M of the inverter In2. Thus, the potential of the working electrode W1 is controlled to coincide with the threshold voltage V _M of the inverter In2, the potential difference between the reference electrode R and the working electrode W1 is kept at zero.
Here, when the current flowing into the working electrode W1 was I, the output terminal of the inverter In2, the voltage Vout is output obtained by adding the voltage difference component (-I * R1) of the negative feedback resistor R1 to the threshold voltage V _M The

That is, the current value I to the current / voltage conversion by the conversion ratio (-R1), the signal was offset by the threshold voltage V _M is obtained. Therefore, after measuring the output terminal voltage Vout of the inverter In2, by subtracting the threshold voltage V _M from which it is possible to obtain a current value I by dividing by -R1.
To obtain the value of the V _M required at this time, the reference or measurement electrode the potential of R directly, or obtain a separate circuit for outputting a threshold voltage V _M as shown in FIG. 3, using the same You can also That is, according to the configuration shown in FIG. 3, the inverters In1 and In2 and the inverter In4 having substantially the same threshold voltage are used to short-circuit the input and output, and the analog / digital converter 5 is connected to the output terminal. A connected configuration is adopted.

FIG. 5 shows an example of current / voltage conversion characteristics by the inverter In2 used in the current measuring unit 3A. The horizontal axis represents the input current [nA] and the vertical axis represents the output voltage [V] characteristics. and the reference voltage (output voltage when the input current I "0") is consistent with the threshold voltage V _M of the inverter In2.
In addition, for example, when using complementary type inverter according to P-channel and N-channel type transistor, the change characteristic of the output voltage in the vicinity of the threshold voltage V _M is steep, the current / voltage conversion characteristic, in FIG. 5 As shown, a highly sensitive characteristic of about 10 ⁷ V / A can be obtained. As a result, an electrochemical measurement device having a detection capability with a wide dynamic range utilizing the characteristics of the complementary inverter can be provided.

Then, according to the potential measuring unit 3B described above, the inverter In3, since the negative feedback circuit is added by the resistor R2, the input terminal voltage of the inverter In3 is fixed to the threshold voltage V _M of the inverter In3. The second working electrode W2 is connected to the input terminal of the inverter In3 via a constant value resistor R3.
Here, the single input resistance of the inverter In3 is usually very large and can be ignored. The input resistance of the potential measuring unit 3B is determined by the two resistors R2 and R3. Therefore, the input resistance of the potential measuring unit 3B can be increased by designing the values of the resistors R2 and R3 to be large.

As described above, the negative feedback circuit of resistors R2, an input terminal voltage of the inverter In3 is controlled so as to coincide with the threshold voltage V _M. Further, since the single input resistance of the inverter In3 is very large, an equal current flows through the resistors R2 and R3 according to Kirchhoff's law. As a result, when the potential of the working electrode W2 is V _W2 , the potential Vout of the output terminal of the inverter Tn3 is as shown in the following formula 1.
Vout = V _M − (R2 / R3) (V _W2 −V _M ) Equation 1

That is, the potential difference between the reference electrode R and the working electrode W2, gain - amplified by (R2 / R3), the signal obtained by offset V _M is obtained. Thus, by measuring the potential Vout of the output terminal of the inverter In3, after subtraction of the threshold voltage V _M therefrom, - it is possible to obtain a potential difference V _W2 -V _M by dividing by (R2 / R3).
To obtain the value of the V _M required at this time, the reference or measurement electrode the potential of R directly, or as described with reference to FIG. 1, it is possible to utilize the circuit configuration shown in FIG.

FIG. 6 shows an example of voltage amplification characteristics by the inverter In3 used in the potential measuring unit 3B. The horizontal axis indicates the input voltage [V], and the vertical axis indicates the output voltage [V]. voltage (output voltage when the input voltage is "0") is consistent with the threshold voltage V _M of the inverter In3. The example shown in FIG. 6 shows an example in which the gain determined by the ratio of the feedback resistor R2 and the input resistor R3 of the inverter In3 is about five times.

FIG. 2 shows a form of an electrochemical measuring device in the case where only the potential measuring unit 3B is provided as the front end circuit 3.
In this case, the counter electrode C of the electrochemical cell 2 can be omitted. The input / output of the inverter In1 constituting the reference electrode potential control circuit 1 is short-circuited, and the input terminal of the inverter In1 is connected to the reference electrode R of the electrochemical cell 2. With this configuration, the threshold voltage V _M by the inverter In1 is a reference electrode R are applied.

The front end circuit 3 has the same configuration as that of the potential measuring unit 3B shown in FIG. Therefore, the operation is as described with reference to FIG. 1, and a duplicate description is omitted.
Also in the electrochemical measuring apparatus shown in FIG. 2, the inverters In1 and In3, it is preferable to use one having generally equal threshold voltage V _M.

  FIG. 7 shows an example in which a complementary circuit is configured as an inverter. A P-channel organic thin film transistor (hereinafter also simply referred to as a P-type organic TFT) is used as the first transistor Tr1, and the second transistor Tr2 is used. N-channel organic thin film transistors (hereinafter also simply referred to as N-type organic TFTs) are used.

That is, the gate electrodes of the first transistor Tr1 and the second transistor Tr2 are commonly connected to form a voltage input terminal Vin, and the source electrode of the first transistor Tr1 and the drain electrode of the second transistor Tr2 are commonly connected. Thus, the voltage output terminal Vout of the complementary circuit is configured.
Further, the operating power supply + Vdd is applied to the drain electrode of the first transistor Tr1, and the source electrode of the second transistor Tr2 is connected to a reference potential point (ground).

In the complementary circuit shown in FIG. 7, the output voltage provided to the output terminal Vout can be changed in the range of the operation power supply Vdd in accordance with the gate input voltage supplied to the input terminal Vin. was as acts as the value of the gate input voltage supplied to the input terminal Vin is inverted operation in the boundary threshold voltage V _M is made.

  FIG. 8 shows a stacked configuration example of the P-type organic TFT as the first transistor Tr1. This example is a general configuration of a field effect type organic transistor. To manufacture this transistor, for example, a PEN film with a thickness of 125 μm is bonded to a glass plate using a heat-resistant double-sided tape, and a device is formed. The substrate 11 is to be manufactured.

  Aluminum to be the gate electrode 12 is vacuum-deposited on the substrate 11 with a film thickness of 3 nm, and then a cross-linkable polyvinyl phenol to be the gate insulating film 13 is formed thereon by spin coating so as to have a film thickness of 300 nm. Film. Next, after a gold electrode is formed on the entire surface, pattern formation is performed in the shape of the source electrode 14 and the drain electrode 15 using photolithography. Finally, as the P-type organic semiconductor layer 16, P-type organic TFT can be obtained by vacuum-depositing pentacene with a film thickness of 50 nm.

  FIG. 9 shows an example of a stacked structure of the N-type organic TFT as the second transistor Tr2. This example also constitutes a field effect type organic transistor, and the same procedure as that of the above-described P-type organic TFT is adopted in the production of the N-type organic TFT.

That is, for example, a PEN film having a thickness of 125 μm is bonded to a glass plate using a heat-resistant double-sided tape to form a substrate 21 for manufacturing a device.
Aluminum to be the gate electrode 22 is vacuum-deposited on the substrate 21 with a film thickness of 30 nm, and then a cross-linkable polyvinyl phenol to be the gate insulating film 23 is formed thereon by spin coating so as to have a film thickness of 300 nm. Film.

  Next, after a gold electrode is formed on the entire surface, pattern formation is performed in the shape of the source electrode 24 and the drain electrode 25 using photolithography. Finally, an N-type organic TFT can be obtained by vacuum-depositing FPTBBT (Chemical Communication, Vo1.46, Page 3265) with a film thickness of 50 nm as the N-type organic semiconductor layer 26.

According to the inverter composed of the organic thin film transistor described above, it can be formed on a flexible material such as a plastic film in a room temperature atmosphere, and is realized as a lightweight and flexible electronic device at low cost. be able to.
By the way, the current N-type organic TFT has a problem that it is poor in stability as a device and easily deteriorates as compared with a P-type organic TFT. For this reason, in consideration of durability and reliability, it is desirable to configure the inverter only with the P-type organic TFT.

  10 to 13 show specific examples in which an inverter is configured using only P-type organic TFTs. First, in FIG. 10, P-type organic TFTs are used as the first and second transistors Tr1 and Tr2, the operation power supply + Vdd is applied to the drain electrode of the first transistor Tr1, and the gate electrode of the first transistor Tr1 is voltage input. A terminal Vin is configured.

The source electrode of the first transistor Tr1 and the drain electrode of the second transistor Tr2 are connected to form a voltage output terminal Vout, and the source electrode of the second transistor Tr2 is connected to a reference potential point (ground). The drain electrode and the gate electrode of the second transistor Tr2 are short-circuited. That is, in the second transistor Tr2, the gap between the gate electrode and the source electrode is used as a diode.
According to this configuration, in response to the gate input voltage supplied to the input terminal Vin, and the threshold voltage V _M to the boundary, the output voltage resulting from the output terminal Vout acts as inverting operation.

Also in the configuration of the inverter shown in FIG. 11, P-type organic TFTs are used as the first and second transistors Tr1 and Tr2, and the circuit configuration is substantially the same as that shown in FIG.
In the example shown in FIG. 11, the gate electrode and the source electrode of the second transistor Tr2 are short-circuited, and the drain electrode and the gate electrode of the second transistor Tr2 are used as a diode.
In this configuration, according to the gate input voltage supplied to the input terminal Vin, and the threshold voltage V _M to the boundary, the output voltage resulting from the output terminal Vout acts as inverting operation.

The inverter shown in FIG. 12 includes a first transistor Tr1 formed of a P-type organic TFT and a resistor R4. An operating power supply + Vdd is applied to the drain electrode of the first transistor Tr1, and its source electrode is a voltage output terminal. Vout is configured and grounded via a resistor R4.
In this configuration, according to the gate input voltage supplied to the input terminal Vin, so that the first transistor Tr1 is a switching operation to the boundary of the threshold voltage V _M, the output voltage resulting from the output terminal Vout is inverted operation Act on.

The inverter shown in FIG. 13 includes first to fourth transistors Tr1 to Tr4 made of P-type organic TFTs.
The drain and source electrodes of the first and second transistors Tr1 and Tr2 are connected in series between the operating power supplies Vdd and Vss, respectively, and the drain and gate electrodes of the second transistor Tr2 are short-circuited. The drain and source electrodes of the third and fourth transistors Tr3 and Tr4 are connected in series between the operating power supply Vdd and the reference potential GND, respectively, and the drain electrode of the second transistor Tr2 is connected to the gate electrode of the fourth transistor Tr4. Has been.
In addition, the gate electrodes of the first and third transistors Tr1 and Tr3 are connected to the input voltage terminal Vin, and the connection point between the source electrode and the drain electrode of the third and fourth transistors Tr3 and Tr4 is connected to the voltage output terminal Vout. It is composed.

According to the circuit configuration shown in FIG. 13, the fourth transistor Tr4 is substantially operated as an N-type TFT by the combination of the first transistor Tr1, the second transistor Tr2 functioning as a diode, and the fourth transistor Tr4. Thus, the third and fourth transistors Tr3 and Tr4 operate as complementary circuits (CMOS). Therefore, the circuit configuration shown in FIG. 13 can be called a pseudo complementary circuit.
Also in the configuration shown in FIG. 13, the function as an inverter in which the output voltage provided from the output terminal Vout is inverted in accordance with the gate input voltage supplied to the input terminal Vin can be achieved.

  Since the inverter using the organic thin-film transistor described above can be formed on a flexible material as described above, it is used by sticking it to a part of the human body, for example, taking advantage of the characteristics of a flexible electronic device. It can be utilized as a wearable electronic device that can be used. Thereby, it becomes possible to greatly expand the utilization range of the above-described electrochemical measurement apparatus, and it is possible to contribute to its practical use.

DESCRIPTION OF SYMBOLS 1 Reference electrode potential control circuit 2 Electrochemical cell 3 Front end circuit 3A Current measurement part 3B Potential measurement part 4,5 Analog / digital converter R Reference electrode C Counter electrode W Working electrode W1 First working electrode W2 Second working electrode E1 Voltage Source In1 to In4 Inverter R1 to R4 Resistance Tr1 to Tr4 Organic thin film transistor Vin Inverter input terminal Vout Inverter output terminal Op1 to Op4 Operational amplifier

Claims (7)

An electrochemical cell that includes at least a reference electrode and a working electrode, and is filled with a sample electrolyte between the reference electrode and the working electrode;
A reference electrode potential control circuit for supplying a threshold voltage of the inverter to a reference electrode of the electrochemical cell using an inverter;
A front end circuit that uses at least one other inverter different from the inverter and provides a current value or a voltage value received at a working electrode of the electrochemical cell as a voltage value to an output terminal of the inverter;
The inverter used for the reference electrode potential control circuit and the inverter used for the front end circuit have the same threshold voltage, and the inverter used for the front end circuit forms an inverter by forming a negative feedback circuit. The electrochemical measuring device is characterized in that the input terminal is set to the threshold voltage of the inverter.   2. The electrochemical measurement apparatus according to claim 1, wherein an analog / digital conversion circuit that converts an output terminal voltage of the inverter into a digital signal is connected to the front end circuit.   The inverter used in the reference electrode potential control circuit is configured such that the output terminal of the inverter is connected to the input terminal to form a negative feedback circuit, and the threshold voltage of the inverter generated at the input terminal is supplied to the reference electrode. The electrochemical measuring device according to claim 1 or claim 2, wherein   The electrochemical cell is further provided with a counter electrode, and an output terminal of an inverter used in the reference electrode potential control circuit is connected to the counter electrode, and an input terminal of the inverter is connected to a reference electrode, thereby providing a negative feedback circuit. The electrochemical measurement device according to claim 1, wherein a threshold voltage of an inverter generated at the input terminal is supplied to the reference electrode.   The front end circuit includes a negative feedback resistor R1 between an output terminal and an input terminal of the inverter, and by connecting the working electrode W to the input terminal of the inverter, a current value generated in the working electrode is obtained. The electrochemical measuring device according to any one of claims 1 to 4, further comprising a current measuring function for converting the output terminal as a voltage value.   The front end circuit includes a negative feedback resistor R3 between the output terminal and the input terminal of the inverter, and an input resistor R2 between the working electrode W and the inverter input terminal. The electrochemical measurement according to any one of claims 1 to 4, further comprising a potential measurement function for amplifying a potential difference generated between the inverter input terminal and the inverter output terminal as a voltage value. apparatus.   7. The electrochemical measurement device according to claim 1, wherein each inverter used in the reference electrode potential control circuit and the front-end circuit is configured by an organic thin film transistor. 8.

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