JP6843375B2 - Organic field effect transistor - Google Patents

Description

The present invention relates to an organic field effect transistor, and more particularly to an organic field effect transistor that produces an output signal having a non-linear response characteristic.

Conventionally, the performance of signal transmission may be improved by adding noise to a system having a non-linear response characteristic. This phenomenon is called stochastic resonance, and it is attracting attention as it can effectively utilize noise that has been considered unnecessary. However, it was difficult to apply because there is an optimum noise intensity and the performance changes significantly as the noise intensity changes. Collins et al. Showed that stochastic resonance is effective for a wide range of noise intensities by connecting a large number of systems in parallel (see Non-Patent Document 1), and Patent Document 1 describes a method used for amplifying a weak signal. It is disclosed.

J.J.Collins, C.C.Chow and T.T.Imhoff, `` Stochastic resonance without tuning ", Nature, vol.376, pp.236-238, 20 July, 1995.

Japanese Unexamined Patent Publication No. 2009-212551

However, the technique described in Patent Document 1 has problems that a large number of systems are required, the overall size is enlarged, and the performance is greatly changed due to a change in noise intensity.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an organic field effect transistor capable of generating a robust output signal with respect to noise of an input signal with a simple configuration. And.

In order to achieve the above object, the organic field effect transistor according to the first invention is an output signal having a non-linear response characteristic with respect to an input signal, and generates and outputs an output signal to which internal noise is added. In the organic field effect transistor, the fluctuation of the output signal due to the external noise included in the input signal is equal to or less than a predetermined value.

According to the organic field effect transistor according to the first invention, it is an output signal having a non-linear response characteristic with respect to the input signal, and is included in the external signal when the output signal to which the internal noise is added is generated. The fluctuation of the output signal due to noise becomes equal to or less than a predetermined value. In this way, gentle stochastic resonance occurs, and signal transmission is possible with almost constant performance regardless of the noise contained in the input.

The organic field effect transistor according to the second invention is an output signal having a non-linear response characteristic with respect to an input signal, and is an organic field effect transistor that generates and outputs an output signal to which internal noise is added. The larger the internal noise added to the output signal, the smaller the fluctuation of the output signal due to the external noise included in the input signal.

According to the organic electric field effect transistor according to the second invention, it is an output signal having a non-linear response characteristic with respect to an input signal, and is added to the output signal when generating an output signal to which internal noise is added. The larger the internal noise, the smaller the fluctuation of the output signal due to the external noise contained in the input signal. In this way, gentle stochastic resonance occurs, and signal transmission is possible with almost constant performance regardless of the noise contained in the input.

As described above, according to the organic electric field effect transistor of the present invention, an output signal to which internal noise is added is generated, stochastic resonance is generated, and fluctuation of the output signal due to external noise contained in the input signal is predetermined. The smaller the value or the larger the internal noise added to the output signal, the smaller the fluctuation of the output signal due to the external noise contained in the input signal. On the other hand, the effect that a robust output signal can be generated can be obtained.

It is a perspective view which shows the structure of the organic field effect transistor which concerns on embodiment of this invention. It is the schematic which shows the functional structure of the organic field effect transistor which concerns on embodiment of this invention. It is a circuit diagram which shows the structure of the nonlinear response system of the organic field effect transistor which concerns on embodiment of this invention. It is a graph which shows the input / output characteristic of the organic field effect transistor which concerns on embodiment of this invention. It is a graph which shows the change of the input / output correlation coefficient with respect to the change of the intensity of external noise. It is a figure which shows the simulation result when the dimensionless parameter D of the distance from a threshold value to an input signal is D <0. It is a figure which shows the simulation result when the dimensionless parameter D of the distance from a threshold value to an input signal is D <0. It is a figure which shows the simulation result when the dimensionless parameter D of the distance from a threshold value to an input signal is D = 0. It is a figure which shows the simulation result when the dimensionless parameter D of the distance from a threshold value to an input signal is D> 0. It is a graph which shows the input / output characteristic of the organic field effect transistor in an experiment. It is a graph which shows the change of the input / output correlation coefficient with respect to the change of the intensity of external noise in the experimental result.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the organic field effect transistor 10 according to the embodiment of the present invention is a semiconductor element having a bottom contact-top gate structure. The semiconductor layer 26 is formed so as to be buried between the gaps of the source / drain electrodes 24, and the insulating layer 28 and the gate electrode 30 are laminated in this order on the semiconductor layer 26.

As shown in FIG. 2, the organic field effect transistor 10 functionally includes a non-linear response system 12, and outputs the output of the non-linear response system 12 by adding internal noise.

The internal noise has a constant intensity, and the organic field effect transistor 10 adds the internal noise to the output signal of the nonlinear response system 12 to add the internal noise to the output signal. The output signal to which the internal noise is added becomes the output of the organic field effect transistor 10.

As shown in FIG. 3, the organic field effect transistor 10 is a drain grounded amplifier circuit that transmits an analog signal, and the gate terminal of the organic field effect transistor 10 has a voltage V _{signal + noise obtained by adding an input signal and noise.} Is input, and a bias voltage V _DD is applied to the drain terminal. A load resistor 22 is connected to the source terminal, grounded via the load resistor 22, and the voltage of the source terminal is _output as an output signal V output.

Next, the operation of the organic field effect transistor 10 according to the present embodiment will be described.

First, when an input signal to which external noise is added is input to the organic field effect transistor 10, the nonlinear response system 12 outputs an output signal having a nonlinear response characteristic with respect to the input signal.

Further, internal noise having a constant intensity is added to the output signal from the nonlinear response system 12, and the signal is output from the organic field effect transistor 10.

For example, when the bias voltage V _DD = -15V and the load resistance 22 is 4.4 kΩ, the input / output characteristics as shown in FIG. 4 can be obtained. It shows a non-linear response to the input signal and shows internal noise.

Further, when external noise is added at the same time as the input signal, the signal transmission performance as shown in FIG. 5 can be obtained. FIG. 5 shows the change in signal transmission performance when the intensity of external noise is changed. As an index of signal transmission performance, the correlation coefficient between the input signal and the output signal is used here. In the organic field effect transistor 10, gentle stochastic resonance occurs, the input / output correlation coefficient is almost constant even if the external noise intensity increases, and signal transmission is possible with almost constant performance regardless of the noise contained in the input. Yes, a noise-robust effect can be obtained.

<Example>
First, the evaluation of the noise robust effect will be described. Here, the noise robust effect is to reduce the fluctuation of the signal transduction ability due to external noise, and the signal transduction ability is the correlation coefficient C between the input / output signals.

An index of the magnitude of fluctuation in signal transduction ability due to external noise is used as the evaluation quantity, and for example, the correlation ratio η ² by regression analysis is used as the evaluation quantity. As a result, it is sufficient to search for a condition in which ^{η 2 is small.}

However, x _ij represents a factor (for example, external noise intensity) in each condition and each trial, T _j represents the average of the factors under the condition j, and G represents the total average of the factors.

Further, each parameter of external noise intensity V _noise , internal noise intensity σ, input signal intensity V _signal , input dc bias V _bias , input / output characteristic inclination A, and input / output characteristic threshold V _th is made dimensionless.

However, when the input / output characteristics are expressed by the following formula,

The internal noise intensity σ is expressed by the following equation.

The dimensionless parameter E of the external noise intensity is expressed by the following equation.

The dimensionless parameter I of the internal noise intensity is expressed by the following equation.

The dimensionless parameter D of the distance from the threshold value to the input signal is expressed by the following equation.

The dimensionless parameter A'of the slope of the input / output characteristic is expressed by the following equation.

Next, the conditions under which the noise robustness effect is effective will be described.

As a condition in which the noise robustness effect is effective, a condition having the following condition 1 and condition 2-1 or condition 2-2 is suitable.

Condition 1: Have a certain level of signal transduction ability. That is, the correlation coefficient C ≠ 0, and for example, C ≧ 0.2.

Condition 2-1: The fluctuation of the signal transmission ability due to external noise is small here. That is, η ² is small, for example, η ² ≤ 0.05.

Condition 2-2: The fluctuation of the signal transduction ability is reduced by applying the internal noise. That is, the larger the internal noise, the ^{smaller η 2.}

Further, the dimensionless parameter D of the distance from the threshold value to the input signal is made variable, and the correlation coefficient C between the input / output signals and the magnitude of the fluctuation of the signal transmission ability due to the external noise with respect to the internal noise intensity and the external noise intensity are evaluated. A simulation was performed to obtain the quantity (correlation ratio) η ^2.

6 and 7 show simulation results when the dimensionless parameter D of the distance from the threshold value to the input signal is D <0. FIG. 6 shows the simulation result when D is smaller.

^{From the above simulation results, the region where the evaluation amount η 2} regarding the magnitude of the fluctuation of the signal transduction ability due to external noise is low and the correlation coefficient C between the input / output signals is high is represented by the following equation (1). ..

E≤20 and E≤I / (-A'D) and I≤20A'D ² ... (1)

^{Further, the region where the evaluation amount η 2} regarding the magnitude of the fluctuation of the signal transduction ability due to the external noise is high but the fluctuation is small due to the internal noise is expressed by the following equation (2).

E ≤ 20 and I ≥ 20 A'D ² and E ≥ 20 / 3-14 log ₁₀ (3-A' ^-0.4 x I ^0.4 ) ... (2)

FIG. 8 shows the simulation result when the dimensionless parameter D of the distance from the threshold value to the input signal is D = 0, and FIG. 9 shows the simulation result when the dimensionless parameter D of the distance from the threshold value to the input signal is D> 0. The simulation result at a certain time is shown.

^{From the above simulation results, the evaluation amount η 2} regarding the magnitude of the fluctuation of the signal transduction ability due to the external noise is high, but the region where the fluctuation of the internal noise is small is expressed by the following equation (3).

E ≦ 20 and E ≧ 20/3 ^{× 10 D /} _{3-14log 10} (3-A ′ ^-0.4 × I ^0.4 )
... (3)

From the above, by configuring the organic electric field effect transistor 10 so as to satisfy the above equation (1), gentle stochastic resonance occurs so that the fluctuation of the output signal due to the external noise contained in the input signal becomes small, and the external Even if the noise intensity increases, the input / output correlation coefficient is almost constant, and signal transmission is possible with almost constant performance regardless of the noise contained in the input.

Further, by configuring the organic electric field effect transistor 10 so as to satisfy the above equation (2) or (3), the larger the internal noise, the smaller the fluctuation of the output signal due to the external noise included in the input signal. In addition, gentle stochastic resonance occurs, and the input / output correlation coefficient is almost constant even if the external noise intensity increases, and signal transmission is possible with almost constant performance regardless of the noise contained in the input.

<Experimental example>
The result of conducting an experiment to obtain the input / output correlation coefficient when the external noise intensity is changed by the method according to the embodiment of the present invention and the conventional technique using stochastic resonance will be described.

Here, as shown in FIG. 10, the input / output characteristics such that the output value is uniquely determined with respect to the conventional input value, and the input / output in which noise of a certain intensity is further added to have internal noise. The characteristics and were used.

As shown in FIG. 11, in the conventional technique using the input / output characteristics without internal noise, the input / output correlation coefficient changes significantly with respect to the change in the input external noise intensity. When the input bias is 0,2,4V, the fluctuation values are about 0.8, 0.8, and 0.3, respectively, and the signal transduction ability changes greatly due to noise. In particular, the noise intensity _{changes significantly from 0 to 10 V PP} , with a change of 0.2 or more.

On the other hand, in the method according to the embodiment of the present invention, the fluctuation of the input / output correlation coefficient is about 0.2 at the maximum, and it has a constant signal transduction ability with respect to external noise. By giving the organic field effect transistor 10 internal noise in this way, a gentle stochastic resonance effect can be obtained, and robustness (homeostasis) with respect to input noise is improved.

As described above, according to the organic electric field effect transistor according to the present embodiment, an output signal having a non-linear response characteristic is generated with respect to the input signal, internal noise is added, and stochastic resonance is generated. Therefore, it is possible to generate an output signal robust to the noise of the input signal with a simple configuration. Further, when the embodiment of the present invention is applied to a detection sensor that detects a weak biological signal derived from a human, an output signal robust to noise of an input signal can be generated, and thus the human origin. It is possible to accurately detect the weak biological signal of.

In the above embodiment, a case where a semiconductor element having a bottom contact-top gate structure is used as the organic field effect transistor has been described as an example, but the present invention is not limited to this, and the noise robust effect is effective. A semiconductor element having another structure may be used as long as it is an organic field effect transistor satisfying the conditions.

10 Organic field effect transistor 12 Non-linear response system 22 Load resistance

Claims (2)

An organic field-effect transistor that has a non-linear response characteristic to an input signal and has an input / output characteristic that generates and outputs an output signal to which internal noise that causes stochastic resonance is added.
The fluctuation of the output signal due to external noise contained in the input signal is equal to or less than a predetermined value.
An organic field effect transistor that satisfies the conditions shown in the following equation when the value obtained by subtracting the input signal voltage and the threshold voltage from the bias of the input signal is a negative value.
E ≦ 20 and E ≦ I / (−A ′ D) and I ≦ 20A ′ D ²
However, E indicates the external noise intensity normalized by the input signal voltage, I indicates the internal noise intensity normalized by the input signal voltage, and A'indicates the gradient included in the nonlinear response characteristic. The value obtained by multiplying the voltage is indicated, and D indicates a value obtained by subtracting the input signal voltage and the threshold voltage from the bias of the input signal and normalizing the value with the input signal voltage. The organic field effect transistor according to claim 1, wherein the input signal is received by the gate terminal, a bias voltage is applied to the drain terminal, and the voltage of the source terminal is output as the output signal.