JP2009031223A - Compensating circuit, probe system, probe system kit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simply-configured compensating circuit which can compensate frequency characteristic of a probe. <P>SOLUTION: An invented compensating circuit is to compensate frequency characteristic of a probe, which is equipped with an operational amplifier having an inverting input terminal, a non-inverting input terminal and output terminal, and an OP impedance section arranged between the above inverting input terminal and the above output terminal. The above inverting input terminal is the terminal to receive signal input from the above probe; the above non-inverting input terminal is the terminal to be grounded, and the above output terminal is the terminal to output signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a compensation circuit for compensating frequency characteristics of a probe, a probe device having a probe and a compensation circuit, and a probe device kit.

A conventional probe 1 will be described with reference to FIG. FIG. 8 is a configuration diagram of a conventional probe.
The probe 1 has a probe tip 3, a probe output terminal 5, and a probe GND terminal 7. A first impedance portion Z ₁ is provided between the probe tip 3 and the probe output terminal 5, and a second impedance portion Z ₂ is provided between the probe output terminal 5 and the probe GND terminal 7.

In the probe 1 having such a configuration, the relationship of the expression (1) is established between the voltage Vin applied to the probe tip 3 and the voltage Vout output to the probe output terminal 5 (in the following expression, Z ₁ And Z ₂ indicate the impedance of the first impedance part Z ₁ and the second impedance part Z ₂ , respectively.
Vout / Vin = Z ₂ / (Z ₁ + Z ₂ ) (1)

When Z ₁ and Z ₂ have only a resistance component, the value of Vout / Vin is constant regardless of the frequency of Vin, but at least one of Z ₁ and Z _{2 is} a capacitance component or In the case of having an inductance component, the value of Vout / Vin depends on the frequency of Vin. In this case, overshoot occurs in the waveform of Vout (see FIG. 9) or hunting occurs, and the waveform of Vin cannot be measured accurately.

Therefore, in order to compensate the frequency characteristics of the probe 1, as shown in FIG. 10, a compensation circuit 9 having an impedance part Z _B is connected to the probe output terminal 5 (see, for example, Patent Document 1).

In this case, the relationship of Expression (2) is established between the voltage Vin and the voltage Vout (in Expression (2), Z _B represents the impedance of the impedance portion Z _B ).
_{Vout / Vin = Z X / (} Z 1 + Z X) (2)
(However, 1 / Z _X = 1 / Z ₂ + 1 / Z _B. )
JP-A-8-86808

Since Vout / Vin is expressed by a complicated expression such as Expression (2), it is extremely difficult to set Z _B so that the value of Vout / Vin becomes constant regardless of the frequency of Vin. Therefore, it is common to configure Z _B with a complex circuit that adjusts the impedance for each frequency, and adjust it by intuition and experience.

  The present invention has been made in view of such circumstances, and provides a compensation circuit capable of compensating the frequency characteristics of a probe with a simple configuration.

Means for Solving the Problems and Effects of the Invention

  The compensation circuit of the present invention is a compensation circuit for compensating the frequency characteristics of a probe, and is provided between an inverting input terminal, an output terminal and an operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal. The inverting input terminal is a terminal that receives a signal input from the probe, the non-inverting input terminal is a grounded terminal, and the output terminal outputs a signal. It is a terminal to do.

  According to the compensation circuit of the present invention, since the output of the operational amplifier is fed back to the inverting input terminal via the OP impedance unit, the potential of the inverting input terminal of the operational amplifier becomes equal to the potential of the non-inverting input terminal. Since the non-inverting input terminal is grounded, the potential of the inverting input terminal is always the GND potential, so that the potential of the probe output terminal is always the GND potential. For this reason, the frequency characteristic of the probe is compensated by configuring the impedance part between the probe tip and the probe output terminal and the OP impedance part between the inverting input terminal and the output terminal of the operational amplifier in a similar circuit. This can simplify the configuration of the compensation circuit.

  Also, since the potential between the probe output terminal and the inverting input terminal of the operational amplifier is always the GND potential, the influence of the stray capacitance of the cable that electrically connects the probe output terminal and the inverting input terminal of the operational amplifier should be ignored. Can do. This facilitates long-distance transmission of signals from the probe.

Further, the present invention is a probe device including the probe and the compensation circuit described above, wherein the probe is provided between a probe tip, a probe output terminal, and the probe tip and the probe output terminal. The probe output terminal and the inverting input terminal of the operational amplifier are electrically connected,
The OP impedance unit and the first impedance unit are configured by circuits similar to each other.

  Moreover, this invention is a probe apparatus kit which has a probe and the compensation circuit of Claim 1, Comprising: The said probe is a probe front-end | tip part, a probe output terminal, the said probe front-end | tip part, and the said probe output terminal. The probe output terminal is a terminal electrically connected to the inverting input terminal of the operational amplifier, and the OP impedance part and the first impedance part are similar to each other. There is also provided a probe device kit comprising a simple circuit.

The probe may include a probe GND terminal that is a terminal to be grounded, and a second impedance portion provided between the probe output terminal and the probe GND terminal.
The configurations shown here can be combined with each other.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The contents shown in the drawings and the following description are examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

1. Configuration of Compensation Circuit and Probe Device A compensation circuit 9 and a probe device 11 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a compensation circuit 9 and a probe device 11 according to an embodiment of the present invention.

The compensation circuit 9 of this embodiment is a compensation circuit 9 for compensating the frequency characteristics of the probe 1, and includes an operational amplifier 19 having an inverting input terminal 13, a non-inverting input terminal 15, and an output terminal 17, and an inverting input terminal 13. And an OP impedance part Z _B provided between the output terminals 17. The non-inverting input terminal 15 is grounded.

The probe device 11 of the present embodiment is a probe device 11 having a probe 1 and a compensation circuit 9. The probe 1 includes a probe tip portion 3, a probe output terminal 5, a probe tip portion 3, and a probe output. The first impedance portion Z ₁ provided between the terminal 5 and the probe output terminal 5 and the inverting input terminal 13 of the operational amplifier 19 are electrically connected. The probe 1 also includes a probe GND terminal 7 and a second impedance portion Z ₂ between the probe output terminal 5 and the probe GND terminal 7. The probe GND terminal 7 is grounded. The probe device 11 electrically connects the probe output terminal 5 of the probe 1 included in the probe device kit including the probe 1 and the compensation circuit 9 that are electrically separated from each other and the inverting input terminal 13 of the operational amplifier 19 in the compensation circuit 9. It can be configured by connecting to.

In the compensation circuit 9, since the output of the operational amplifier 19 is fed back to the inverting input terminal 13 via the OP impedance part Z _B , the potential of the inverting input terminal 13 of the operational amplifier 19 becomes equal to the potential of the non-inverting input terminal 15. Since the non-inverting input terminal 15 is grounded, the potential of the inverting input terminal 13 is always the GND potential, whereby the potential of the probe output terminal 5 is always the GND potential.

In the probe apparatus 11 configured as shown in FIG. 1, the relationship of Expression (3) is established between the voltage Vin applied to the probe tip 3 and the voltage Vout output from the output terminal 17 of the operational amplifier 19 (hereinafter referred to as the expression (3)). In the equation, Z _B represents the impedance of the OP impedance portion Z _B. )
Vout / Vin = −Z _B / Z ₁ (3)

It can be seen that Equation (3) does not include the impedance of the second impedance part Z ₂ and is much simpler than Equation (2). The reason why Equation (3) is in such a simple form is that no voltage is applied to the second impedance portion Z ₂ because the potential of the probe output terminal 5 is always the GND potential. Thus, since the compensation circuit 9 of the present embodiment has an effect that the influence of the second impedance unit Z ₂ can be eliminated, the compensation circuit 9 of the present embodiment includes the probe 1 having the second impedance unit Z ₂ , That is, the voltage signal attenuated by Z ₂ / (Z ₁ + Z ₂ ) times is suitably used for compensating the frequency characteristics of the probe 1 (for example, the probe 1) output from the probe output terminal 5.

In addition, since the potential between the probe output terminal 5 and the inverting input terminal 13 is always the GND potential, the compensation circuit 9 of this embodiment can be used to electrically connect the inverting input terminal 13 to the probe output terminal 5. The influence of the stray capacitance of the connected cable can be ignored, and the signal from the probe 1 can be easily transmitted over a long distance.
As described above, the compensation circuit 9 of the present embodiment is preferably used to compensate the frequency characteristics of the probe 1 having the second impedance unit Z ₂ , but the second impedance unit Z ₂ as shown in FIG. It can also be used to compensate for the frequency characteristics of the probe 1 that does not have. Even in this case, it is possible to obtain an effect that the influence of the stray capacitance of the cable that electrically connects the probe output terminal 5 and the inverting input terminal 13 can be ignored.

In order to compensate the frequency characteristics of the probe 1, the OP impedance part Z _B and the first impedance part Z ₁ are similar to each other so that Vout / Vin in the equation (3) is constant regardless of the frequency of Vin. What is necessary is just to comprise with a circuit. In other words, “circuits similar to each other” are circuits whose impedance ratio does not depend on frequency. In this case, Z _B = Z ₁ / N (N is a positive value independent of the frequency), and Expression (3) is expressed by the following expression.
Vout / Vin = −Z _B / Z ₁ = −1 / N

This equation shows that the signal attenuation ratio can be freely adjusted by adjusting Z _B / Z ₁ , and further, the signal can be amplified by making N smaller than 1.

An example of a circuit similar to each other is a case where R ₂ = R ₁ / N and C ₂ = NC _{1 in} the circuit as shown in FIG. In this case, the impedances of the first impedance part Z ₁ and the OP impedance part Z _B are expressed by the following equations.
Z ₁ = R ₁ / (1 + jωC ₁ R ₁ )
Z _B = R ₂ / (1 + jωC ₂ R ₂ ) = R ₂ / (1 + jωC ₁ R ₁ )

According to this equation, Z _B = Z ₁ / (R ₁ / R ₂ ), Z _B = Z ₁ / N, and the first impedance part Z ₁ and the OP impedance part Z _B are configured by similar circuits. I understand that.

In general, circuits similar to each other can be obtained by increasing the resistance value of each resistor by 1 / N times and increasing the capacitance value of each capacitor by N times. For example, in the circuit as shown in FIG. 4, if R ₃ = R ₁ / N, R ₄ = R ₂ / N, C ₃ = NC ₁ , C ₄ = NC ₂ , then Z _B = Z ₁ / N, The 1 impedance part Z ₁ and the OP impedance part Z _B are similar to each other.

3 and 4, the first impedance part Z ₁ and the OP impedance part Z _B have the same arrangement of circuit elements (resistors, capacitors, inductors) and circuit constants (resistance value, capacitance value, inductance value). However, the circuit elements may be arranged differently as shown in FIG. Circuit Z _B of FIG. 5, since the circuit equivalent of Z _B of _{R 5 = 2R 3, C 5} = C 3/2 to the Figure 4, in this case, the first impedance unit Z ₁ and OP It can be said that the impedance part Z _B is composed of similar circuits.

2. Procedure for Compensating Probe Frequency Characteristics Next, a procedure for compensating the frequency characteristics of the probe 1 will be described.
Compensation of the frequency characteristics of the probe 1 starts by first determining the circuit configuration of the first impedance part Z ₁ of the probe 1. An example of a circuit configuration determination method is as follows: (1) Using a spectrum analyzer, measure the frequency characteristics of the output from the probe output terminal 5 without the compensation circuit 9; (2) Next, the physical properties of the probe 1 The position of the stray capacitance is estimated from the general configuration, and the arrangement of the circuit elements of the first and second impedance portions Z ₁ and Z ₂ of the probe 1 is estimated as shown in FIG. 6, for example. (3) Next, FIG. The circuit constants R _{6 to} R ₈ and C _{6 to} C ₈ are determined so that the frequency characteristic of the output of the circuit 6 matches the frequency characteristic of the output from the probe output terminal 5, thereby determining the first and the first of the probe 1. The circuit configuration of the second impedance parts Z ₁ and Z ₂ is determined.

Then, the first impedance unit Z ₁ and the circuit configuration of a probe 1 determines the arrangement and the circuit constants of the circuit elements of the OP impedance unit Z _B to be similar. The circuit constant is determined so that the attenuation rate of the signal becomes a desired value.

FIG. 7 shows an example of the first and second impedance units Z ₁ and Z ₂ obtained by the method shown here, and the OP impedance unit Z _B determined so that the circuit configuration is similar to the first impedance unit Z _1. An example is shown. Z _B was determined so that the attenuation rate was 4000: 1. When simulation was performed with the circuit shown in FIG. 7, the frequency characteristics of the probe 1 were appropriately compensated.

The description so far has been made by taking as an example the case where the first impedance unit Z ₁ and the OP impedance unit Z _B are each composed of only a resistor and a capacitor, but the first impedance unit Z ₁ and the OP impedance unit Z _{B are described.} Each may include an inductor.
In addition, each circuit element constituting the OP impedance unit Z _B may have variable circuit constants. In this case, it becomes easy to make the circuit configurations of the first impedance part Z ₁ and the OP impedance part Z _B similar to each other.

It is a block diagram of the compensation circuit and probe apparatus of one Embodiment of this invention. It is a block diagram of the compensation circuit and probe apparatus of another embodiment of this invention. It is a specific example of the circuit structure of the 1st impedance part in the compensation circuit of FIG. 1, and a probe apparatus, and OP impedance part. It is another specific example of the circuit structure of the 1st impedance part in the compensation circuit of FIG. 1, and a probe apparatus, and OP impedance part. 6 is still another specific example of the circuit configuration of the compensation circuit and the first impedance unit and the OP impedance unit in the probe device of FIG. 1. It is a block diagram which shows arrangement | positioning of the circuit element estimated from the physical structure of a probe. Specific examples of the compensation circuit and the probe device of the present invention are shown. It is a block diagram of the conventional probe. An example of the frequency characteristic of the conventional probe is shown. 9 shows a state where a conventional compensation circuit is attached to the probe of FIG.

Explanation of symbols

1: Probe 3: Probe tip 5: Probe output terminal 7: Probe GND terminal 9: Compensation circuit 11: Probe device 13: Inverted input terminal 15: Non-inverted input terminal 17: Output terminal of operational amplifier 19: Operational amplifier Z ₁ : No. 1 impedance part Z ₂ : second impedance part Z _B : OP impedance part

Claims (5)

A compensation circuit for compensating the frequency characteristics of the probe,
An operational amplifier having an inverting input terminal, a non-inverting input terminal and an output terminal, and an OP impedance unit provided between the inverting input terminal and the output terminal;
The compensation circuit, wherein the inverting input terminal is a terminal that receives an input of a signal from the probe, the non-inverting input terminal is a terminal that is grounded, and the output terminal is a terminal that outputs a signal. A probe apparatus comprising a probe and the compensation circuit according to claim 1,
The probe has a probe tip, a probe output terminal, and a first impedance part provided between the probe tip and the probe output terminal,
The probe output terminal and the inverting input terminal of the operational amplifier are electrically connected,
The probe apparatus, wherein the OP impedance unit and the first impedance unit are configured by similar circuits. The probe device according to claim 2, wherein the probe includes a probe GND terminal that is a grounded terminal, and a second impedance unit provided between the probe output terminal and the probe GND terminal. A probe device kit comprising a probe and the compensation circuit according to claim 1,
The probe has a probe tip, a probe output terminal, and a first impedance part provided between the probe tip and the probe output terminal,
The probe output terminal is a terminal electrically connected to the inverting input terminal of the operational amplifier,
The probe device kit, wherein the OP impedance unit and the first impedance unit are configured by similar circuits. 5. The probe device kit according to claim 4, wherein the probe includes a probe GND terminal which is a terminal to be grounded, and a second impedance portion provided between the probe output terminal and the probe GND terminal.

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