JPWO2010041606A1 - Comparator, noise generator, and stochastic resonator - Google Patents

Abstract

Provided are a hysteresis comparator, a noise generator, and a stochastic resonator using the same that can greatly reduce the circuit scale. When the voltage Vs across the phase transition resistance element exceeds the threshold value Vth1, the crystal structure of the phase transition resistance element Rv undergoes a structural phase transition and changes from monoclinic to tetragonal, resulting in a relatively low resistance state. . As a result, the transistor Q1 is turned on, and a high-level output voltage Vout is output from the output terminal Tout. On the other hand, when the voltage Vs applied across the phase change resistance element Rv falls below the threshold value Vth2, the phase change resistance element Rv undergoes a structural phase transition and changes from tetragonal to monoclinic, and has a relatively high resistance. It becomes a state. As a result, the transistor Q1 is turned off, and the low-level output voltage Vout is output from the output terminal Tout.

Description

  The present invention relates to a comparator, a noise generator, and a stochastic resonator using these.

  In recent years, with the demand for downsizing of electronic devices, simplification of comparators and noise generators, which are basic elements of electronic circuits, has become an important technical item. For example, Patent Document 1 discloses a hysteresis comparator using seven MOSFETs. Patent Document 2 discloses a decoding noise generator for the purpose of easily and stably generating a decoded noise signal having an arbitrary characteristic.

  In recent years, researches have been conducted to construct various systems that simulate the behavior of living organisms using stochastic resonators. Here, the stochastic resonator includes a noise generator that generates a noise signal, and a comparator that superimposes the noise signal generated by the noise generator on a weak input signal and compares the signal with a predetermined threshold value.

  However, as shown in Patent Document 1, a conventional comparator employs a configuration mainly composed of a transistor in which a plurality of transistors are combined. Therefore, there is a certain limit in reducing the circuit scale. For example, in Patent Document 1, although the circuit scale is reduced, at least seven transistors are required. Further, in Patent Document 2, no consideration is given to reducing the circuit scale, and only the circuit configuration of the block diagram level is disclosed, and any circuit element is used. There is no specific description about this.

JP 2008-5547 A JP 2006-80879 A

  An object of the present invention is to provide a hysteresis comparator, a noise generator, and a stochastic resonator using the same that can greatly reduce the circuit scale.

  A comparator according to one aspect of the present invention includes a phase change resistance element whose resistance value changes between a relatively high resistance state and a low resistance state by a structural phase transition, and a load resistor connected in series to the phase change resistance element And.

  According to another aspect of the present invention, a noise generator includes a phase change resistance element whose resistance value is changed between a relatively high resistance state and a low resistance state by a structural phase transition, and a series connection with the phase change resistance element. A load resistor connected thereto; a power source connected in series to the phase change resistance element and the load resistance; and an output terminal provided between the phase change resistance element and the load resistance.

  Further, a stochastic resonator according to another aspect of the present invention includes a noise generator, a comparator that superimposes the noise signal generated by the noise generator and an input signal, and compares the superimposed signal with a predetermined threshold value. And at least one of the noise generator and the comparator includes a phase transition resistance element whose resistance value changes between a relatively high resistance state and a low resistance state by a structural phase transition.

It is a circuit diagram which shows the whole structure of the comparator by Embodiment 1 of this invention. It is the graph which showed the resistance-temperature characteristic of the vanadium oxide employ | adopted as the phase change resistance element of FIG. It is a graph which shows the current-voltage characteristic of vanadium oxide. 3 is a graph showing input / output characteristics of the comparator shown in FIG. 1. It is a wave form diagram which shows the result of the experiment conducted about the comparator shown in FIG. It is a graph which shows the input-output characteristic of the phase change resistive element in the experiment conducted about the comparator shown in FIG. It is the graph which showed the waveform of the output signal in the experiment conducted about the comparator shown in FIG. It is a circuit diagram which shows the other comparator in Embodiment 1 of this invention. It is a circuit diagram which shows another comparator in Embodiment 1 of this invention. A circuit diagram of a MOS resistor is shown. It is a circuit diagram which shows another comparator in Embodiment 1 of this invention. It is a circuit diagram which shows another comparator in Embodiment 1 of this invention. It is a circuit diagram which shows another comparator by Embodiment 1 of this invention. It is a circuit diagram which shows the whole structure of the comparator by Embodiment 2 of this invention. It is the graph which showed the input / output characteristic of the comparator shown in FIG. It is a circuit diagram which shows the whole structure of the noise generator by Embodiment 3 of this invention. It is a graph which shows the experimental result of the experiment conducted about the noise generator shown in FIG. It is the graph which showed the temperature-resistance characteristic of the phase change resistive element used for the experiment shown in FIG. In the experiment shown in FIG. 17, it is a graph which shows the electric current-voltage characteristic between electrodes when the resistance value of load resistance is set to 0 (ohm). (A), (B) is a graph which shows the current-voltage characteristic when the resistance value of load resistance is 220 ohms and the electric current between electrodes is changed in the noise generator shown in FIG. (A)-(D) showed the voltage between electrodes when the electric current of 0.012A, 0.013A, 0.016A, and 0.017A each flowed between electrodes in the experiment of FIG. It is a graph. In the noise generator shown in FIG. 16, it is a graph which shows the current-voltage characteristic between electrodes when resistance value of load resistance is 100 ohms, 180 ohms, and 470 ohms. The noise generator shown in FIG. 16 is configured using actual circuit elements, and the resistance between the load resistors is 0Ω, 82Ω, 100Ω, 120Ω, and 180Ω. -A graph showing voltage characteristics. The noise generator shown in FIG. 16 is configured using actual circuit elements, and the resistance between the load resistors is 220Ω, 270Ω, 330Ω, 390Ω, 470Ω, and the current between the electrodes when the same experiment as in FIG. 22 is performed. -A graph showing voltage characteristics. It is the graph which showed the relationship between the electric current width and load resistance of the area where the voltage which generate | occur | produces in FIGS. It is a circuit diagram which shows the whole structure of the noise generator by Embodiment 4 of this invention. (A), (B) is a schematic diagram of the power spectrum of the noise signal output from the output terminal of the noise generator shown in FIG. (A), (B) is a schematic diagram of the power spectrum of the noise signal output from the output terminal of the noise generator shown in FIG. It is a block diagram which shows the whole structure of the stochastic resonator by Embodiment 5 of this invention. It is a circuit diagram which shows the whole structure of the stochastic resonator by Embodiment 5 of this invention. (A), (B) is a wave form diagram explaining operation | movement of the stochastic resonator shown in FIG.

(Embodiment 1)
The comparator according to Embodiment 1 of the present invention will be described below. FIG. 1 is a circuit diagram showing an overall configuration of a comparator according to the first embodiment of the present invention. As shown in FIG. 1, the comparator includes an input terminal T1, a phase change resistance element Rv, a load resistance R1, a drive circuit DR, and an output terminal Tout.

The input terminal Vin receives the input voltage Vin and outputs it to the phase change resistance element Rv. The phase change resistance element Rv is connected between the input terminal T1 and the load resistance R1. In the present embodiment, for example, vanadium oxide (VO ₂ ) is used as the phase transition resistance element Rv, but is not limited to this, and a relatively high resistance state and a low resistance state are caused by the structural phase transition. Various substances whose resistance values change can be adopted.

Specifically, V ₂ O ₃ , Ti ₂ O ₃ , RNiO ₃ (R = Pr, Nd), Li _1-x M _x Ti ₂ O ₄ (M = Mg, Mn), Fe ₃ O ₄ , NbO _{2 , V 3 O 5, V n} O 2n-1 (n = 4~8), Ti n O 2n-1 (n = 4~9), La 2 NiO 4 (n = 1 in La n + 1 Ni n O 3n + 1) , M ₂ MO ₂ O _7-y (M = Nd, Sm, Gd) can be used.

  The drive circuit DR is driven based on the voltage input to the control terminal Tg, and includes a transistor Q1 and a resistor R2. The transistor Q1 is composed of, for example, an npn-type bipolar transistor, the base as the control terminal Tg is connected to the connection point between the phase change resistance element Rv and the load resistance R1, and the emitter is connected to the ground via the resistor R2. The collector is connected to the voltage source Vdd. The output terminal Tout is connected to the emitter of the transistor Q1 and outputs the output voltage Vout.

  FIG. 2 is a graph showing the resistance-temperature characteristics of vanadium oxide employed in the phase change resistance element Rv of FIG. 1, the vertical axis shows resistance (Ω), and the horizontal axis shows temperature (K). FIG. 3 is a graph showing the current-voltage characteristics of vanadium oxide. The vertical axis represents current (A) and the horizontal axis represents voltage (V).

As shown in FIG. 2, vanadium oxide has a monoclinic crystal structure in a region where the temperature is about 300K or lower, and has a resistance value of the order of 10 ⁴ to 10 ⁵ and is in a relatively high resistance state. On the other hand, when the temperature exceeds about 340 K, a structural phase transition occurs and the crystal structure changes from monoclinic to tetragonal. Therefore, the resistance value is relatively low resistance state of 10 to 10 ^two orders in the region of more than about 340K. Thus, vanadium oxide has a characteristic that the resistance value changes about 1000 times due to the structural phase transition.

  Further, as shown in FIG. 3, vanadium oxide is in a relatively high resistance state until the voltage exceeds about 5.5 V (threshold value Vth1) in the monoclinic crystal state. A relatively small current flows.

  When the voltage exceeds about 5.5 V, a structural phase transition occurs and the crystal structure changes from monoclinic to tetragonal. As a result, the resistance value sharply decreases and a relatively low resistance state is reached, so that a relatively large current of 0.1 A or more flows. In this experiment, the maximum current flowing for sample protection is set to 0.1A.

  On the other hand, when the voltage falls below about 3 V (threshold value Vth2), a structural phase transition occurs, and the crystal structure changes from tetragonal to monoclinic. As a result, a relatively high resistance state is obtained, and a relatively small current of about 0 to 0.025 A flows.

  Thus, vanadium oxide can change its state to tetragonal or monoclinic by changing the voltage, and can be in a relatively high resistance state and a low resistance state. . Vanadium oxide has a hysteresis so that the crystal structure changes from monoclinic to tetragonal when the voltage exceeds the positive threshold Vth1, and the crystal structure changes from tetragonal to monoclinic when the voltage falls below the negative threshold Vth2. You can see that

  Therefore, the present inventor constructed a comparator using the characteristics of vanadium oxide. The hysteresis width W of the current-voltage characteristic shown in FIG. 3 can be reduced to 0 when the degree of uniformity of the vanadium oxide crystallinity is increased, and can be increased when the degree of uniformity of the crystallinity is lowered. Can do. Therefore, by adjusting the degree of uniformity of vanadium oxide crystallinity, this comparator can be configured as a comparator with hysteresis having a desired hysteresis width W or as a comparator without hysteresis. Can do.

  FIG. 4 is a graph showing the input / output characteristics of the comparator shown in FIG. 1. The vertical axis shows the output voltage Vout, and the horizontal axis shows the input voltage Vin.

  When the input voltage Vin exceeding the positive threshold value VTH1 of the comparator is input from the input terminal T1 and the voltage Vs applied to both ends of the phase change resistance element exceeds the threshold value Vth1 shown in FIG. 3, the phase change resistance element Rv is structured. A phase transition occurs to change from monoclinic to tetragonal, resulting in a relatively low resistance state. As a result, a relatively large current flows through the phase change resistance element Rv, the voltage applied to both ends of the load resistance R1 increases, and a high level voltage is input to the control terminal Tg. Therefore, the transistor Q1 is turned on, and the high-level output voltage Vout is output from the output terminal Tout.

  On the other hand, when the input voltage Vin lower than the negative threshold value VTH2 of the comparator is input from the input terminal T1 and the voltage Vs applied across the phase change resistance element Rv is lower than the threshold value Vth2 shown in FIG. 3, the phase change resistance element Rv undergoes a structural phase transition and changes from tetragonal to monoclinic, resulting in a relatively high resistance state. As a result, a relatively small current flows through the phase change resistance element Rv, the voltage Vs applied across the load resistor R1 is lowered, and a low-level voltage is input to the control terminal Tg. Therefore, the transistor Q1 is turned off, and the low-level output voltage Vout is output from the output terminal Tout.

  FIG. 5 is a waveform diagram showing the results of an experiment performed on the comparator shown in FIG. The right vertical axis represents the input voltage Vin input to the input terminal T1, and the left vertical axis represents the output signal (V) input to the control terminal Tg. G1 represents a waveform diagram of the input voltage Vin, G2 represents a waveform diagram of an output signal, and G3 represents an output voltage Vout.

  As the input voltage Vin, a sine wave having a frequency of 10 Hz, an offset voltage of 3 V, and an amplitude of 0 V to 8 V was used. Further, as the load resistance R1, one having a resistance value of 13.4Ω was adopted. Then, the amplitude of the input voltage Vin was gradually increased with time.

  As shown in FIG. 5, when G1 exceeds the threshold value VTH1, it can be seen that the amplitude of G2 increases rapidly, G3 also increases rapidly, and the comparator is turned on. Further, when G1 falls below the threshold value VTH2 (not shown), it can be seen that the amplitude of G2 returns to the original magnitude, G3 decreases rapidly, and the comparator is in the OFF state. As shown in the graph of FIG. 5, it can be seen that the ratio of the amplitude in the OFF state of G2 to the amplitude in the ON state is about 0.7 / 0.3 = 2.33. In order to surely turn on / off the transistor Q1, it is preferable that this ratio is large.

  Next, another experiment performed on the comparator shown in FIG. 1 will be described. FIG. 6 shows the input / output characteristics of the phase change resistance element Rv in another experiment. The horizontal axis represents the input voltage Vin input to the input terminal T1, and the vertical axis represents the output signal (V) input to the control terminal Tg. FIG. 7 is a graph showing the waveform of the output signal in this other experiment. The horizontal axis represents time (seconds), and the vertical axis represents the output signal (V).

  In this other experiment, a sine wave having a frequency of 10 Hz, an offset voltage of 1.5 V, and an amplitude of 0 V to 6 V was adopted as the input voltage Vin. A load resistance R1 having a resistance value of 131.5Ω was used. Then, the amplitude of the input voltage Vin was gradually increased as time passed.

  As shown in FIG. 7, in this other experiment, the ratio of the amplitude of the output signal in the on state to the amplitude in the off state is about 3 / 0.5 = 6, and the experiment shown in FIG. It can be seen that the ratio is larger than that of FIG.

  Thus, according to the present comparator, since the phase change resistance element Rv is mainly used without using the transistor as a main component, the circuit scale can be greatly reduced as compared with the comparator mainly using the conventional transistor.

  In this embodiment, a bipolar transistor is employed as the transistor Q1, but the present invention is not limited to this, and a field effect transistor such as a MOSFET may be employed. Further, although the n-type transistor is used as the transistor Q1, it is not limited to this and a p-type transistor may be used.

  Further, in the present embodiment, the following comparator may be employed. FIG. 8 is a circuit diagram showing another comparator according to the first embodiment of the present invention. In the comparator of FIG. 1, a bipolar transistor is used as the transistor Q1 of the drive circuit DR. However, in the drive circuit DR shown in FIG. 8, for example, an n-channel MOS field effect transistor is used as the transistor Q1. In this case, the drive circuit DR has a source follower type circuit configuration. That is, the gate of the transistor Q1 serves as the control terminal Tg, the source is connected to the output terminal Tout and grounded via the resistor R2, and the drain is connected to the voltage source Vdd.

  Thus, by making the drive circuit DR have a source follower type circuit configuration, it is possible to increase the input impedance and simultaneously reduce the output impedance. As a result, the influence of the drive circuit DR on other circuits can be reduced, and the drive circuit DR can drive more loads.

  FIG. 9 is a circuit diagram of still another comparator according to Embodiment 1 of the present invention. In the comparator shown in FIG. 9, the drive circuit DR has an open drain type circuit configuration. In other words, the drive circuit DR includes a resistor R2 and a transistor Q1 formed of, for example, an n-channel MOS field effect type. The resistor R2 has one end connected to the voltage source Vdd and the other end connected to the drain of the transistor Q1. The transistor Q1 has a source grounded, a drain connected to the output terminal Tout, and a gate serving as a control terminal Tg.

  In the drive circuit DR shown in FIG. 9, a resistor element may be used as the resistor R2, or a MOS resistor as shown in FIG. 10 may be used. As shown in FIG. 10, the MOS resistor is composed of a MOS field effect transistor having a gate connected to the drain and the voltage source Vdd, and a source connected to the transistor Q1.

  FIG. 11 is a circuit diagram showing still another comparator according to the first embodiment of the present invention. In the comparator shown in FIG. 11, the driving circuit DR has a CMOS gate type circuit configuration. That is, the drive circuit DR is configured by a CMOS transistor including a transistor Q1 configured by an n-channel field effect transistor and a transistor Q2 configured by a p-channel field effect transistor. Transistors Q1 and Q2 have drains connected to each other and gates connected to each other. The source of the transistor Q2 is connected to the voltage source Vdd, and the source of the transistor Q1 is grounded.

  Further, as the comparator in the present embodiment, a pull-down connection type circuit configuration in which the phase change resistance element Rv is grounded as shown in FIGS. 12 and 13 may be employed. FIG. 12 is a circuit diagram showing still another comparator according to the first embodiment of the present invention. In the comparator shown in FIG. 12, one end of the phase change resistance element Rv is grounded, and the other end is connected to the input terminal T1 via the load resistance R1. The connection point between the load resistor R1 and the phase change resistance element Rv is connected to the gate which is the control terminal Tg of the transistor Q1. The drive circuit DR shown in FIG. 12 has the same configuration as the drive circuit DR shown in FIG.

  In the comparator of FIG. 12, a resistor R4 for applying a bias voltage may be connected in parallel to the phase change resistance element Rv. Further, as the resistor R4, a MOS resistor shown in FIG. 10 may be adopted. When the transistor Q2 illustrated in FIG. 10 is applied to the resistor R4 in FIG. 12, the drain of the transistor Q2 may be connected to the control terminal Tg and the source may be grounded.

  FIG. 13 is a circuit diagram showing an example of still another comparator according to the first embodiment of the present invention. In the comparator shown in FIG. 13, the connection relationship between the phase change resistance element Rv and the load resistance R1 is the same as that in FIG. The drive circuit DR has an open drain type circuit configuration shown in FIG. In the comparator shown in FIG. 13 as well, a resistor R4 may be connected in parallel to the phase change resistance element Rv, as in FIG. Note that the comparators shown in FIGS. 8 to 13 may be employed as comparators in the embodiments described below.

(Embodiment 2)
The comparator according to the second embodiment of the present invention is characterized in that an offset terminal (an example of a second input terminal) to which an offset voltage is input is provided. FIG. 14 is a circuit diagram showing the overall configuration of the comparator according to the second embodiment of the present invention. In the present embodiment, the same elements as those in the first embodiment are not described.

  As shown in FIG. 14, the comparator includes an offset terminal T2 and a ground resistor R3, compared to the comparator shown in FIG. The ground resistor R3 is connected between the load resistor R1 and the ground. The offset terminal T2 is connected to a connection point between the ground resistor R3 and the load resistor R1, and receives the offset voltage Vofs. Here, a DC voltage supplied from a constant voltage circuit is employed as the offset voltage Vofs.

  FIG. 15 is a graph showing the input / output characteristics of the comparator shown in FIG. 14. The vertical axis represents the output voltage Vout, and the horizontal axis represents the input voltage Vin. In the comparator shown in FIG. 14, since the offset voltage Vofs is input to the offset terminal T2, as shown in FIG. 15, the threshold values VTH1 and VTH2 are shifted to the negative side compared to the threshold values VTH1 and VTH2 shown in FIG. Can do. Therefore, the threshold value VTH1 and the threshold value VTH2 can be set so as to cross 0 by adjusting the value of the offset voltage to an appropriate value.

(Embodiment 3)
Next, a noise generator according to Embodiment 3 of the present invention will be described. In the present embodiment, the same elements as those in the first and second embodiments are not described.

  FIG. 16 is a circuit diagram showing an overall configuration of a noise generator according to Embodiment 3 of the present invention. The noise generator includes a phase change resistance element Rv and a load resistance R1 connected in series to the phase change resistance element Rv. An output terminal Tout is connected to a connection point between the phase change resistance element Rv and the load resistance R1.

  A power supply is connected to both ends of the series circuit of the phase change resistance element Rv and the load resistance R1, and the voltage Vin1 is applied.

  In the noise generator configured as described above, the phase change resistance element Rv can be oscillated by setting the resistance value of the load resistor R1 to an appropriate value. That is, when the phase transition resistance element Rv undergoes a structural phase transition from monoclinic to tetragonal and is in a low resistance state, the load resistance R1 causes the voltage Vs of the phase transition resistance element Rv to be less than or equal to the threshold Vth2. If it has a resistance value, the phase change resistance element Rv is in a high resistance state. On the other hand, when the phase change resistance element Rv is in a high resistance state, if the load resistance R1 has a resistance value such that the voltage Vs of the phase change resistance element Rv is equal to or higher than the threshold value Vth1, the phase change resistance element Rv is in a low resistance state. Therefore, by setting the load resistance R1 to a resistance value that satisfies both conditions, the phase change resistance element Rv oscillates autonomously repeatedly between a low resistance state and a high resistance state, and the phase change resistance element Rv A noise signal can be taken out.

  As described above, it is possible to provide a noise generator mainly including the phase change resistance element Rv without mainly including a transistor. Here, since the phase change resistance element Rv and the load resistance R1 each have a size of about one transistor, the circuit scale is greatly reduced as compared with a noise generator mainly composed of conventional transistors. Can do.

  Next, an experiment performed on the noise generator shown in FIG. 16 will be described. FIG. 17 is a graph showing an experimental result of an experiment performed on the noise generator shown in FIG. The vertical axis represents the voltage Vs (effective voltage) of the phase change resistance element Rv, and the horizontal axis represents the resistance value of the load resistance R1.

  In this experiment, a constant voltage Vin1 = 20 V is applied between the electrodes P1, P2 at both ends of the phase change resistance element Rv and the load resistance R1, the resistance value of the load resistance R1 is changed, and the voltage of the phase change resistance element Rv is changed. Vs was measured. Further, as the phase change resistance element Rv, one having vanadium oxide as a main component and having a resistance value Rhigh of 2000Ω in a high resistance state and a resistance value Rlow in a low resistance state of 40Ω was adopted. Further, the threshold values of the phase change resistance element Rv are the threshold value Vth1 = 17V and the threshold value Vth2 = 4V. That is, as the phase change resistance element Rv, an element having a low resistance state when the voltage Vs is 17 V or higher and a high resistance state when the voltage Vs is 4 V or lower is employed.

  G1x is a graph showing the relationship between the voltage Vs and the resistance value of the load resistor R1 when the phase change resistance element Rv is in a high resistance state. G2x is a graph showing the relationship between the voltage Vs and the resistance value of the load resistor R1 when the phase change resistance element Rv is in a low resistance state. Gx indicates a graph of FIG. 25 described later.

  G1x decreases almost linearly as the resistance value of the load resistor R1 increases. G1x has a voltage Vs of 17V or more when the load resistance R1 is about 330Ω or less. Therefore, when the resistance value of 330Ω or less is adopted as the load resistance R1, the voltage Vs becomes 17V or more when the phase change resistance element Rv is in a high resistance state. Causes a phase transition. Therefore, the rectangular region D1 having the voltage Vs of 17 V or more and the load resistance R1 of 330Ω or less is an effective voltage region in which the phase change resistance element Rv can be switched from the high resistance state to the low resistance state.

  Further, G2x decreases with a downwardly convex curve as the resistance value of the load resistor R1 increases. G2x has a voltage Vs of 4V or less when the load resistance R1 is about 180Ω or more. For this reason, when a load resistance R1 having a resistance value of 180Ω or more is adopted, the phase transition resistance element Rv has a voltage Vs of 4 V or less when it is in a low resistance state. Causes a phase transition. Therefore, the rectangular region D2 having the voltage Vs of 4 V or less and the load resistance R1 of 180Ω or more is an effective voltage region in which the phase transition resistance element Rv can be switched from the low resistance state to the high resistance state.

  From the above, the load resistance R1 can oscillate the phase change resistance element Rv if the resistance value is 180Ω or more and 330Ω or less.

  That is, the load resistance R1 makes the voltage of the phase transition resistance element Rv equal to or higher than the threshold value Vth1 (first threshold voltage) for returning the voltage to the low resistance state when the phase transition resistance element Rv is in a high resistance state. A resistance value range (a resistance value in the region D1 is 330Ω or less) and a threshold value for returning the voltage of the phase transition resistance element Rv to a high resistance state when the phase transition resistance element Rv is in a low resistance state. It is only necessary to have a resistance value satisfying both resistance value ranges of a resistance value range (a range where the resistance value is 180Ω or more in the region D2) to be Vth2 (second threshold voltage) or less.

  FIG. 18 is a graph showing temperature-resistance characteristics of the phase change resistance element Rv used in the experiment shown in FIG. The vertical axis represents the resistance value (Ω), and the horizontal axis represents the temperature (K). As shown in FIG. 18, when the temperature exceeds about 300K, the phase transition resistance element Rv undergoes a structural phase transition from monoclinic to tetragonal, and from a high resistance state with a resistance value Rhigh = 2000Ω to a low resistance of Rlow = 40Ω. Switch to the state. Further, when the temperature falls below about 340 K, a structural phase transition occurs from tetragonal to monoclinic, and the low resistance state with a resistance value Rlow = 40Ω switches to the high resistance state with a resistance value Rhigh = 2000Ω.

  FIG. 19 is a graph showing current-voltage characteristics between the electrodes P1 and P2 when the resistance value of the load resistor R1 is set to 0Ω in the experiment shown in FIG. The vertical axis represents the voltage (V) between the electrodes P1 and P2, and the horizontal axis represents the current (A). When the load resistance R1 is 0Ω, when the phase transition resistance element Rv is in a high resistance state, the voltage between the electrodes P1 and P2 is 17V or less and the voltage Vs cannot reach 17V. The resistive element Rv maintains a high resistance state without causing a structural phase transition. Further, when the phase change resistance element Rv is in a low resistance state, the voltage between the electrodes P1 and P2 is larger than 4V and the voltage Vs does not become 4V or less. Therefore, the phase change resistance element Rv does not cause structural phase transition. Maintain a low resistance state. Therefore, when the load resistance R1 is 0Ω, the phase change resistance element Rv does not oscillate.

  20A and 20B are graphs showing current-voltage characteristics when the resistance value of the load resistor R1 is 220Ω and the current between the electrodes P1 and P2 is changed in the noise generator shown in FIG. FIG. 20B is a graph showing an enlarged section of the current of 0.012 A to 0.017 A in FIG. 20A and 20B, the vertical axis represents voltage (V), and the horizontal axis represents current (A).

  As shown in FIGS. 20A and 20B, the voltage between the electrodes P1 and P2 fluctuates in the section where the current flowing between the electrodes P1 and P2 is 0.013A to 0.016A, and a noise signal is generated. You can see that In addition, it can be seen that the fluctuation center voltage gradually decreases as the current increases in this section.

  FIGS. 21A to 21D show electrodes P1 when 0.012A, 0.013A, 0.016A, and 0.017A currents are passed between the electrodes P1 and P2 for 2 seconds in the experiment of FIG. , P2 is a graph showing the voltage between P2.

  When the current is 0.012 A and 0.017 A, the voltages are constant at about 19 V and 8 V, respectively, and it can be seen that no noise signal is generated. On the other hand, when the current is 0.013 A and 0.016 A, the peak-to-peak voltage ΔV fluctuates at about 3.0 V and about 2.0 V, respectively, and it can be seen that a noise signal is generated.

  From the above, in the experiment of FIG. 20, when the current flowing between the electrodes P1 and P2 is about 0.013 A or more and about 0.016 A or less, a noise signal can be generated, but the electrodes P1 and P2 are generated. It can be seen that a noise signal cannot be generated when the current flowing between them is less than about 0.013 A or greater than about 0.016 A.

  FIG. 22 is a graph showing current-voltage characteristics between the electrodes P1 and P2 when the resistance value of the load resistor R1 is 100Ω, 180Ω, and 470Ω in the noise generator shown in FIG. The vertical axis represents voltage (V), and the horizontal axis represents current (A).

  22, when the current-voltage characteristic between the electrodes P1 and P2 when the noise generator shown in FIG. 16 is configured by a circuit simulator is measured, and the noise generator shown in FIG. 16 is configured using actual circuit elements. The current-voltage characteristics between the electrodes P1 and P2 were measured.

  G11 shows an experimental result by an actual circuit element when the resistance value of the load resistor R1 is 100Ω, and G12 shows an experimental result by a circuit simulator when the resistance value of the load resistor R1 is 100Ω.

  G21 shows an experimental result by an actual circuit element when the resistance value of the load resistor R1 is 180Ω, and G22 shows an experimental result by a circuit simulator when the resistance value of the load resistor R1 is 180Ω.

  G31 shows an experimental result by an actual circuit element when the resistance value of the load resistor R1 is 470Ω, and G32 shows an experimental result by a circuit simulator when the resistance value of the load resistor R1 is 470Ω.

  As shown in FIG. 22, it can be seen that almost the same experimental results are obtained when the circuit simulator is used and when it is configured by actual circuit elements. As shown in G21 and G22, when the resistance value of the load resistor R1 is 180Ω, it can be seen that the voltage fluctuates and the noise signal is generated in the section where the current is 0.13A to 0.016A. On the other hand, as shown in G11, G12, G31, and G32, when the resistance value of the load resistor R1 is 100Ω and 470Ω, when the current exceeds about 0.012A, unlike the case where the resistance value is 180Ω, It can be seen that the voltage drops sharply without generating a fluctuation section and no noise signal is generated.

  FIG. 23 shows a case where the noise generator shown in FIG. 16 is configured using actual circuit elements, and the resistance value of the load resistor R1 is 0Ω, 82Ω, 100Ω, 120Ω, and 180Ω, and the same experiment as FIG. 22 is performed. 4 is a graph showing current-voltage characteristics between electrodes P1 and P2.

  In FIG. 23, G41 to G45 indicate cases where the resistance value of the load resistor R1 is 0Ω, 82Ω, 100Ω, 120Ω, and 180Ω, respectively.

  As shown in G45, when the resistance value of the load resistor R1 is 180Ω, it can be seen that the voltage fluctuates and a noise signal is generated in the section where the current is 0.13A to 0.016A. On the other hand, as shown in G41 to G44, when the resistance value of the load resistor R1 is 0Ω, 82Ω, 100Ω, and 120Ω, the voltage fluctuates when the current exceeds about 0.012 A, unlike the case where the resistance value is 180Ω. It can be seen that the voltage drops sharply without generating a section, and no noise signal is generated.

  FIG. 24 shows a case where the noise generator shown in FIG. 16 is configured using actual circuit elements, and the resistance value of the load resistor R1 is 220Ω, 270Ω, 330Ω, 390Ω, 470Ω, and an experiment similar to FIG. 4 is a graph showing current-voltage characteristics between electrodes P1 and P2.

  In FIG. 24, G51 to G55 indicate cases where the resistance value of the load resistor R1 is 220Ω, 270Ω, 330Ω, 390Ω, and 470Ω, respectively.

  As shown in G51, G52, and G53, when the resistance value of the load resistor R1 is 220Ω, 270Ω, and 330Ω, the voltage fluctuates and the noise signal is generated in the section where the current is 0.13A to 0.016A. I understand that. On the other hand, as shown in G54 to G55, when the resistance value of the load resistor R1 is 390Ω, 470Ω, the voltage fluctuates when the current exceeds about 0.012A, unlike the resistance values of 220Ω, 270Ω, 330Ω. It can be seen that the voltage drops sharply without generating a section, and no noise signal is generated.

  FIG. 25 is a graph showing the relationship between the current width ΔI and the load resistance R1 in the section where the voltage generated in FIGS. 23 to 24 fluctuates. The vertical axis represents the current width ΔI (mA), and the horizontal axis represents the resistance value of the load resistor R1. Note that points PT1 to PT5 shown in FIG. 25 are obtained by plotting the current width ΔI and the resistance value of the load resistance R1 in G41 to G45 shown in FIG. 23, and points PT6 to PT10 are G51 to G51 shown in FIG. The current width ΔI and the resistance value of the load resistance R1 in each of G55 are plotted.

  As shown in FIG. 25, it can be seen that the current width ΔI is about 0 mA when the resistance value of the load resistor R1 is 120Ω or less or 390Ω or more, and no noise signal is generated. Further, it can be seen that when the resistance value of the load resistor R1 is in the range of 120Ω to 390Ω, the current width ΔI is not 0 and a noise signal is generated. However, in order to stably generate a noise signal, it is necessary to secure a current width ΔI of a certain value or more. For this purpose, it is preferable to set the resistance value of the load resistor R1 to 180Ω to 330Ω.

(Embodiment 4)
The noise generator according to the fourth embodiment of the present invention is characterized in that the noise generator according to the third embodiment is used as one noise unit, and the noise units are connected in parallel. In the present embodiment, the same elements as those in the first to third embodiments are not described.

  FIG. 26 is a circuit diagram showing an overall configuration of a noise generator according to the fourth embodiment of the present invention. The noise generator includes n (n is an integer of 2 or more) noise units U1 to Un and n resistors R21. The noise unit U1 includes a phase change resistance element Rv and a load resistance R1 connected between the phase change resistance element Rv and the ground. Note that the noise units U2 to Un have the same configuration as the noise unit U1, and thus will not be described.

  A voltage source (not shown) is connected to the phase change resistance element Rv via the input terminal TA, and the input voltage VinA is input thereto. The noise units U1 to Un are each connected to the output terminal TB via the resistor R21. Thereby, the noise units U1 to Un are connected in parallel.

  The noise units U1 to Un generate noise signals having frequencies f1 to fn, respectively. Here, the frequencies f1 to fn can be set to desired values by adjusting the resistance value of the load resistor R1 of the noise units U1 to Un and the characteristics of the phase change resistance element Rv, for example. In the present embodiment, the frequencies f1 to fn are increased from U1 to Un. Further, the power of the noise signal output from each of the noise units U1 to Un can be changed by adjusting the level of the input voltage VinA input to the input terminals TA of the noise units U1 to Un, for example.

  The noise generator configured as described above generates noise signals of frequencies f1 to fn from the noise units U1 to Un, synthesizes the noise signals at the connection point CP1, and outputs the synthesized noise signal from the output terminal TB. .

  27A and 27B are schematic diagrams of the power spectrum of the noise signal output from the output terminal TB of the noise generator shown in FIG. 27A and 27B, the input voltage VinA of the same level is input to the input terminals TA of the noise units U1 to Un. Therefore, as shown in FIG. 27A, noise signals having the same power are output from the noise units U1 to Un. Therefore, as shown in FIG. 27B, the noise signal output from the output terminal TB is white noise.

  FIGS. 28A and 28B are schematic diagrams of the power spectrum of the noise signal output from the output terminal TB of the noise generator shown in FIG. In FIGS. 28A and 28B, the input voltage VinA having a lower level is input to each input terminal TA of the noise units U1 to Un from U1 to Un. Therefore, as shown in FIG. 28A, noise signals with smaller power are output from the noise units U1 to Un toward U1 to Un. Therefore, as shown in FIG. 28B, the noise signal output from the output terminal TB becomes color noise whose power decreases as the frequency increases.

  Thus, according to the present noise generator, since the noise units U1 to Un are provided, a noise signal having a desired power spectrum is generated by adjusting the frequency and power of the noise signal output from each noise unit. Can do.

(Embodiment 5)
The stochastic resonator according to the fifth embodiment of the present invention is configured by the comparator shown in the first embodiment and the noise generator shown in the fourth embodiment. In the present embodiment, the description of the same elements as in the first to fourth embodiments will be omitted.

  FIG. 29 is a block diagram showing the overall configuration of the stochastic resonator according to the fifth embodiment of the present invention. As shown in FIG. 29, the stochastic resonator includes a noise generator 100, a comparator 200, and a resistor Rc. Here, at least one of the noise generator 100 and the comparator 200 shown in FIG. 29 includes a phase change resistance element Rv. Specifically, the noise generator of the fourth embodiment has the following configuration.

  FIG. 30 is a circuit diagram showing the overall configuration of the stochastic resonator according to the fifth embodiment of the present invention. In FIG. 30, the noise generator 100 has the same configuration as that of the noise generator of the fourth embodiment, and thus detailed description thereof is omitted. Since the comparator 200 has the same configuration as that of the comparator of the first embodiment, detailed description thereof is omitted. The output terminal TB of the noise generator 100 is connected to the input terminal T1 of the comparator 200 via the resistor Rc.

  31A and 31B are waveform diagrams for explaining the operation of the stochastic resonator shown in FIG. FIG. 31A shows the output voltage Vout from the output terminal Tout, and FIG. 31B shows the input voltage Vin input to the input terminal T1.

  In the stochastic resonator configured as described above, a noise signal generated by the noise generator 100 is generated and input to the comparator 200. The comparator 200 combines this noise signal with the input voltage Vin at the connection point CP2, and generates a combined signal. The comparator 200 outputs a high-level output voltage Vout when the level of the combined signal exceeds the threshold value VTH1. On the other hand, when the level of the composite signal falls below the threshold value VTH2, the comparator 200 outputs a low-level output voltage Vout.

  As described above, when a noise signal is synthesized with a weak input voltage Vin to generate a synthesized signal, and the synthesized signal is subjected to threshold processing, the frequency at which the output voltage Vout becomes a high level increases depending on the level of the input voltage Vin. Become. Therefore, the stochastic resonator can detect a weak noise signal.

  In the stochastic resonator, the noise generator 100 is configured by the noise generator shown in the first embodiment, and the comparator 200 is configured by the comparator shown in the fourth embodiment. Therefore, the circuit scale of the stochastic resonator can be greatly reduced.

  In this stochastic resonator, only the noise generator 100 may be configured by the noise generator shown in the first embodiment, and the comparator 200 may be configured by a comparator mainly including a conventional transistor. Further, only the comparator 200 may be configured by the noise generator shown in the fourth embodiment, and the noise generator 100 may be configured by a conventional noise generator.

  In the stochastic resonator, the noise generator 100 may be configured by the noise generator shown in the third embodiment, and the comparator 200 may be configured by the comparator shown in the second embodiment.

  The technical features of the comparator, the noise generator, and the stochastic resonator can be summarized as follows.

  (1) The comparator includes a phase change resistance element whose resistance value changes between a relatively high resistance state and a low resistance state due to structural phase transition, and a load resistance connected in series to the phase change resistance element. I have.

  According to this configuration, when an input voltage is input to one end of the phase change resistance element and the voltage applied to both ends of the phase change resistance element exceeds a predetermined threshold value, the phase change resistance element causes a structural phase transition and is It changes from an oblique crystal to a tetragonal crystal, resulting in a relatively low resistance state. As a result, a relatively large current flows through the phase change resistance element, the voltage applied to both ends of the load resistance becomes relatively high, and a high level voltage is applied from the connection point between the phase change resistance element and the load resistance. It can be taken out.

  On the other hand, when the voltage applied across the phase change resistance element falls below a predetermined threshold value, the phase change resistance element undergoes a structural phase transition and changes from tetragonal to monoclinic, resulting in a relatively high resistance state. Become. As a result, a relatively small current flows through the phase change resistance element, the voltage applied across the load resistance becomes relatively low, and a low level voltage is applied from the connection point between the phase change resistance element and the load resistance. It can be taken out.

  As described above, a comparator mainly including a phase change resistance element can be provided without mainly including a transistor. Here, since each of the phase change resistance element and the load resistance has a size of about one transistor, the circuit scale can be greatly reduced as compared with a comparator mainly including a conventional transistor.

  (2) In the comparator, the phase transition resistance element preferably has hysteresis in current-voltage characteristics.

  According to this configuration, it is possible to provide the comparator with hysteresis, and it is possible to provide a comparator with hysteresis whose circuit scale is greatly reduced. A phase transition resistance element generally has a different voltage when changing from monoclinic to tetragonal and a voltage when changing from monoclinic to tetragonal. Hysteresis occurs. The width of the hysteresis can be changed by adjusting the crystallinity of the phase change resistance element.

  Specifically, the width of hysteresis can be reduced as the degree of uniformity of crystallinity of the phase change resistance element increases. Therefore, by increasing the degree of uniformity of the crystallinity of the phase change resistance element, the hysteresis width can be reduced to 0. In this case, a comparator having no hysteresis can be configured. On the other hand, a comparator with hysteresis can be configured by reducing the degree of uniformity of crystallinity of the phase change resistance element.

  (3) In the comparator, a control terminal is connected to a connection point between the first input terminal that receives an input voltage and outputs the input voltage to the phase change resistance element, and the phase change resistance element and the load resistance, and the control terminal It is preferable to provide a drive circuit that drives based on the voltage input to the.

  According to this configuration, since the drive circuit is provided, a reverse current flow in which a current flows from the drive circuit to the phase change resistance element side via the control terminal can be prevented, and the operation of the circuit can be stabilized. At the same time, signal input / output is separated, and impedance matching of the circuit can be easily performed. Further, since the output voltage is output through the drive circuit, it is possible to obtain an output voltage in which the high level and the low level are clearly distinguished.

  (4) In the comparator, a ground resistance connected between the load resistance and the ground, and a second input terminal connected to a connection point between the ground resistance and the load resistance, to which an offset voltage is input. It is preferable to provide.

  According to this configuration, by setting the offset voltage to an appropriate value, it is possible to configure a comparator with hysteresis such that the positive threshold value has a positive value and the negative threshold value has a negative value. Can do.

  (5) In the comparator, the phase change resistance element is preferably composed of vanadium oxide.

  According to this configuration, since the vanadium oxide that easily causes the structural phase transition is used, the size of the comparator can be reduced.

  (6) The noise generator includes a phase change resistance element whose resistance value changes between a relatively high resistance state and a low resistance state due to a structural phase transition, and a load resistance connected in series to the phase change resistance element. Preferably, the power supply includes a power supply connected in series to the phase change resistance element and the load resistance, and an output terminal provided between the phase change resistance element and the load resistance.

  According to this configuration, the phase change resistance element can be oscillated by setting the resistance value of the load resistance to an appropriate value. That is, when the phase change resistance element undergoes a structural phase transition from monoclinic to tetragonal and becomes a low resistance state, the load resistance has a resistance value that makes the voltage of the phase change resistance element equal to or less than the threshold value. If so, the phase change resistance element is in a high resistance state. On the other hand, when the phase change resistance element is in a high resistance state, if the load resistance has a resistance value that makes the voltage of the phase change resistance element equal to or higher than a threshold value, the phase change resistance element is in a low resistance state. It becomes. Therefore, by setting the load resistance to a resistance value that satisfies both conditions, the phase change resistance element oscillates autonomously repeating a low resistance state and a high resistance state, and generates a noise signal from the phase change resistance element. It can be taken out.

  As described above, it is possible to provide a noise generator mainly including a phase change resistance element without mainly including a transistor. Here, since each of the phase change resistance element and the load resistance has a size of about one transistor, the circuit scale can be greatly reduced as compared with a noise generator mainly composed of a conventional transistor.

  (7) In the noise generator, when the phase change resistance element is in a high resistance state, the load resistance is equal to or higher than a first threshold voltage for returning the voltage of the phase change resistance element to a low resistance state. And a resistance value range in which, when the phase change resistance element is in a low resistance state, the voltage of the phase change resistance element is set to be equal to or lower than a second threshold voltage for returning to a high resistance state. It is preferable to have a resistance value satisfying both of these resistance value ranges.

  According to this configuration, the phase change resistance element can be oscillated more reliably, and a noise signal can be more reliably extracted from the output terminal.

  (8) In the noise generator, it is preferable that one noise unit is constituted by the phase change resistance element and the load resistance, and a plurality of noise units are provided, and the noise units are connected in parallel.

  According to this configuration, for example, various noise signals can be generated by adjusting the oscillation frequency and power of each noise unit.

  (9) In the noise generator, the phase change resistance element is preferably made of vanadium oxide.

  According to this configuration, since the noise generator is configured by vanadium oxide that easily causes phase transition, a noise signal can be more reliably extracted from the output terminal.

  (10) The stochastic resonator includes a noise generator, a comparator that superimposes a noise signal generated by the noise generator and an input signal, and compares the superimposed signal with a predetermined threshold, and the noise generator and the At least one of the comparators includes a phase change resistance element whose resistance value changes between a relatively high resistance state and a low resistance state due to structural phase transition.

  According to this configuration, since at least one of the noise generator and the comparator is configured by the phase transition resistance element, it is possible to provide a stochastic resonator having a reduced circuit scale.

  (11) The stochastic resonator includes the comparator according to any one of (1) to (5) and the noise generator according to any one of (6) to (9).

  According to this configuration, since the comparator according to any one of (1) to (5) and the noise generator according to any of (6) to (9) are provided, the probability that the circuit scale has been reduced. A resonant element can be provided.

  Since the circuit scale of the comparator, the noise generator, and the stochastic resonator can be reduced, the present invention can be expected to be applied to systems such as the robot electronics field that simulates biological functions. In addition, the present invention is useful for constructing a system that is highly resistant to noise and requires low power consumption and flexible control in a small size. Furthermore, the present invention can be expected to be one of basic element technologies for system-on-chip.

Claims (11)

A phase change resistance element whose resistance value changes between a relatively high resistance state and a low resistance state by a structural phase transition;
And a load resistor connected in series to the phase change resistance element.   The comparator according to claim 1, wherein the phase transition resistance element has hysteresis in current-voltage characteristics. A first input terminal to which an input voltage is input and output to the phase change resistance element;
3. The comparator according to claim 1, further comprising: a drive circuit connected to a connection point between the phase change resistance element and the load resistor, and driven based on a voltage input to the control terminal. . A ground resistance connected between the load resistance and ground;
The comparator according to claim 3, further comprising a second input terminal connected to a connection point between the ground resistance and the load resistance and to which an offset voltage is input.   The comparator according to claim 1, wherein the phase change resistance element is made of vanadium oxide. A phase change resistance element whose resistance value changes between a relatively high resistance state and a low resistance state by a structural phase transition;
A load resistance connected in series to the phase change resistance element;
A power supply connected in series to the phase change resistance element and the load resistance;
A noise generator comprising: an output terminal provided between the phase change resistance element and a load resistance.   The load resistance is a resistance value range in which the voltage of the phase change resistance element is set to be equal to or higher than a first threshold voltage for returning to a low resistance state when the phase change resistance element is in a high resistance state; When the phase change resistance element is in a low resistance state, the resistance satisfying both resistance value ranges of a resistance value range in which the voltage of the phase change resistance element is less than or equal to a second threshold voltage for returning to the high resistance state. The noise generator according to claim 6, wherein the noise generator has a value. The phase change resistance element and the load resistance constitute one noise unit,
With multiple noise units,
8. The noise generator according to claim 6, wherein the noise units are connected in parallel.   The noise generator according to claim 6, wherein the phase change resistance element is made of vanadium oxide. A noise generator,
A comparator that superimposes the noise signal and the input signal generated by the noise generator, and compares the superimposed signal with a predetermined threshold;
At least one of the noise generator and the comparator includes a phase transition resistance element whose resistance value changes between a relatively high resistance state and a low resistance state by a structural phase transition, and a stochastic resonance element . A comparator according to any one of claims 1 to 5;
A stochastic resonator including the noise generator according to claim 6.

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