JP5859378B2 - Charge supply device, charge amplifier, charge amplifier inspection system, sensor system, and communication system - Google Patents

Description

  The present invention relates to a charge supply device, a charge amplifier, a charge amplifier inspection system, a sensor system, and a communication system.

  Charge amplifiers are widely used as means for amplifying weak charge fluctuations in sensor output. For example, the charge amplifier is used as a means for detecting a capacitance change such as acceleration or impact, or a means for detecting excited electrons due to light or radiation. Non-Patent Documents 1 to 3 below describe the configuration and operating principle of the charge amplifier. Patent Document 1 below discloses an invention for improving the performance of a charge amplifier. The role of the charge amplifier is to convert a minute charge amount into a large voltage level. For example, in a charge amplifier that can convert a change in charge of 10 pC into a change in voltage of 1 mV, a conversion gain of 160 dBΩ can be obtained by the following equation (1).

U.S. Pat. No. 4,543,536

“Charge amplifier”, [online], Wikimedia Foundation, [Search May 17, 2012], Internet <http://en.wikipedia.org/wiki/Charge_amplifier> “LTC6240 / LTC6241 / LTC6242”, [online], Linear Technology Corporation, [searched May 17, 2012], Internet <http://cds.linear.com/docs/Datasheet/624012fe.pdf> “OP AMP APPLICATIONS”, [online], Analog Devices, [searched May 17, 2012], Internet <http://www.analog.com/library/analogDialogue/archives/39-05/Web_Ch4_final.pdf>

  A charge amplifier capable of obtaining an enormous amount of amplification is very sensitive to noise, so that it is necessary to consider that noise is not mixed in an input signal. For example, when a current change of 10 pA due to noise occurs in the charge amplifier, a voltage change of 1 mV appears in the output signal. In this case, in the output signal, it becomes difficult to separate a component corresponding to the input signal and a component corresponding to noise, and therefore, it may not be possible to accurately perform processing based on the output signal. In particular, as the wiring connected to the input terminal of the charge amplifier is longer, this wiring acts as an antenna, and noise is more likely to be mixed into the input signal.

  On the other hand, in order to inspect a charge amplifier capable of obtaining such a large amplification amount, it is necessary to supply an input signal having a very weak current value to the input terminal of the charge amplifier. For example, if a current of 10 μA is supplied to a charge amplifier capable of obtaining a conversion gain of 160 dBΩ with a 1 V power supply, the output voltage becomes 1 kV. In this case, since the output voltage of the charge amplifier sticks to 1V, the charge amplifier cannot be normally inspected. In this charge amplifier, in order to keep the output voltage within the range of 1V power supply, it is necessary to supply an input signal of 10 nA to the input terminal of the charge amplifier.

  Here, a conventional charge amplifier inspection system will be described. FIG. 10 shows a configuration of a conventional charge amplifier inspection system. As shown in FIG. 10, the conventional charge amplifier inspection system employs a configuration in which a sensor that is actually used is connected to an input terminal of the charge amplifier. A configuration is also possible in which a device for supplying a weak current is provided instead of the sensor. However, in this configuration, it is difficult to supply an accurate weak current to the charge amplifier so that noise is not mixed.

  For example, in a conventional inspection method, when inspecting a system that detects acceleration or impact, a weak current is generated by connecting the acceleration sensor or impact sensor to the input terminal of the charge amplifier and applying acceleration or impact to the sensor. This weak current was supplied to the charge amplifier.

  In addition, in the conventional inspection method, when a system for detecting radiation or light is inspected, a weak current is generated by connecting the radiation sensor or light sensor to the input terminal of the charge amplifier and irradiating the sensor with radiation or light. This weak current was supplied to the charge amplifier.

  However, in such a conventional inspection method, it is necessary to prepare an actual sensor and it is difficult to generate a weak current having a desired current value. Therefore, it is possible to easily and reliably inspect a charge amplifier. could not. For example, to generate a weak current with a desired current value using an acceleration sensor, connect the actual acceleration sensor to the charge amplifier, and then grasp the relationship between the acceleration and current value in the acceleration sensor. It was necessary to apply acceleration to the accelerometer with accuracy.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an inspection means that can easily and reliably inspect a charge amplifier.

In order to solve the above-described problem, a charge supply device according to the present invention is a charge supply device that supplies a charge for inspection to a charge amplifier, and includes a first input terminal to which a first voltage is input, The first input terminal and the second input terminal selectively select an input terminal having a second input terminal to which a second voltage is input and an output terminal and conducting with the output terminal. A first switch that is switchable to a first capacitor, a capacitor having one electrode connected to the output terminal of the first switch and the other electrode connected to an input terminal of the charge amplifier . The switch further includes a floating third input terminal, and the input terminal connected to the output terminal includes the first input terminal, the second input terminal, and the third input terminal. Can be switched selectively with It is characterized in.

  According to the charge supply device, when the capacitor capacity is Ct and the voltage obtained by the second voltage-the first voltage is VCM, every time the first switch is switched, The charge amount Qt obtained by Ct * VCM can be applied to the charge amplifier. Furthermore, when the capacitance of the feedback capacitor included in the charge amplifier is Cf, the charge amplifier can output an output signal having an output voltage Vo obtained by (Ct / Cf) * VCM.

  When a weak current is supplied to the charge amplifier by the charge supply device, this can be realized by using a capacitor having an extremely small capacity (that is, an area of the capacitor electrode plate is extremely small) as the capacitor. it can.

  For example, when the voltage VCM is 0.1 V, a weak charge of 10 fC can be applied to the charge amplifier by setting the capacitor capacitance Ct to 0.1 pF. Furthermore, by setting the capacitor capacitance Cf to 1 pF, the output voltage Vo can be set to 10 mV.

  Therefore, according to the charge supply device, the charge amplifier can be inspected by a simple control such as switching the first switch without saturating the output voltage Vo.

  Further, according to the charge supply device, by adjusting the switching frequency of the first switch, a current It having a desired current value obtained by the following equation (2) is generated as a current applied to the charge amplifier. Can do.

  For example, when the capacitor capacitance Ct is set to 0.1 pF and the voltage VCM is set to 0.1 V, when it is desired to generate a current of 10 pA, the switching frequency of the first switch is changed to the following formula (2) modified This can be realized by setting the frequency fs (1 kHz) obtained by Expression (3).

  As described above, according to the charge supply device, it is not necessary to prepare a sensor to be actually used, and a weak current having a desired current value can be easily generated. Therefore, the charge amplifier can be easily and reliably inspected. be able to. Even if the sensor to be actually used is already connected to the input terminal of the charge amplifier, it is not necessary to use this sensor for the inspection of the charge amplifier. Furthermore, according to the above-described charge supply device, it is sufficient to include at least the first switch and the capacitor, and the configuration is simple. Therefore, it is possible to reduce the cost related to the inspection of the charge amplifier. Further, according to the charge supply device, since the configuration is simple, the charge supply device can be provided in the vicinity of the input terminal of the charge amplifier, and further can be built in the charge amplifier, so that the input supplied to the charge amplifier The signal path can be made relatively short, and therefore, a configuration in which noise is hardly mixed into the input signal can be realized.

  In the above-described charge supply device, the first switch further includes a floating third input terminal, and the input terminal that is electrically connected to the output terminal is the first input terminal and the second input terminal. And the third input terminal can be selectively switched.

  According to the above configuration, during normal operation (non-testing) of the charge amplifier, by switching the first switch to the third input terminal, one electrode of the capacitor is brought into a floating state, and the parasitic capacitance of the capacitor It is possible to make it difficult for the noise gain due to.

  The charge supply device preferably further includes a second switch provided on a wiring between the capacitor and the charge amplifier and capable of selectively switching connection and disconnection of the wiring.

  According to the above configuration, when the charge amplifier is in a normal operation (non-inspection), the second switch is turned off to disconnect the wiring between the capacitor and the charge amplifier. It is possible to make it difficult for noise gain due to the capacitance to occur.

  In the charge supply device, the first pulse signal is supplied to the first switch, thereby selecting the first input terminal and switching between the second input terminal in the first switch. It is preferable to further comprise a pulse applicator to be controlled.

  According to this configuration, the switching frequency of the first switch can be adjusted by adjusting the frequency of the first pulse signal. Thereby, the current It having a desired current value can be easily generated.

  A charge amplifier according to the present invention includes the above-described charge supply device, and the charge supply device is connected to an input terminal of the charge amplifier.

  According to the charge supply device, it is possible to provide a charge amplifier that has the same effect as the charge supply device.

  Further, the charge amplifier inspection system according to the present invention compares the charge supply device, the output signal of the charge amplifier, and a reference voltage, and outputs a second pulse signal whose comparison result is represented by a pulse. And a vessel.

  According to this configuration, whether the output signal corresponding to the input signal is output by the second pulse signal, and whether the output voltage is amplified to a desired voltage (ie, reference voltage) level. Can be easily and reliably determined.

  In the charge amplifier inspection system, the pass / fail of the charge amplifier is determined by comparing the number of pulses included in the first pulse signal with the number of pulses included in the second pulse signal. It is preferable to further include a pass / fail judgment means.

  According to this configuration, whether or not the output signal according to the input signal is output by a simple process of comparing the number of pulses of the first pulse signal and the number of pulses of the second pulse signal, and It can be determined whether the output signal from the charge amplifier is amplified to a desired voltage level.

  In the charge amplifier inspection system, the noise level of the second pulse signal is detected based on a change in the number of pulses in the second pulse signal, which is generated by gradually changing the level of the reference voltage. It is preferable to further include a noise level detection means.

  According to this configuration, the noise level included in the output signal of the charge amplifier can be detected easily and reliably.

  In the charge amplifier inspection system, signal amplification for detecting a signal amplification factor by the charge amplifier based on a change in the number of pulses in the second pulse signal, which is generated by gradually changing the level of the reference voltage. It is preferable to further comprise a rate detection means.

  According to this configuration, the signal amplification factor by the charge amplifier can be detected easily and reliably.

  The sensor system according to the present invention includes a sensor, a charge amplifier that amplifies an output signal from the sensor, and a signal processing that performs predetermined signal processing based on the output signal amplified by the charge amplifier. And a charge supply device connected to an input terminal of the charge amplifier.

  According to the sensor system, it is possible to provide a sensor system that has the same effect as the charge supply device.

  The communication system according to the present invention includes a receiving unit that receives a signal transmitted from the outside, a charge amplifier that amplifies the signal received by the receiving unit, and the signal amplified by the charge amplifier. On the basis of this, it is characterized by comprising signal processing means for performing predetermined signal processing and the charge supply device connected to the input terminal of the charge amplifier.

  According to the communication system, it is possible to provide a communication system having the same effects as the charge supply device.

  According to the present invention, it is possible to provide an inspection means capable of performing a charge amplifier inspection more easily and reliably.

1 shows a configuration of a charge amplifier inspection system according to a first embodiment of the present invention. 1 shows a configuration of a feedback circuit included in a charge amplifier according to the present embodiment. The structure of the charge amplifier test | inspection system which concerns on 2nd Embodiment of this invention is shown. The structure of the charge amplifier test | inspection system which concerns on 3rd Embodiment of this invention is shown. The structure of the charge amplifier test | inspection system which concerns on 4th Embodiment of this invention is shown. The detection method of the signal amplification factor in the charge amplifier test | inspection system which concerns on 4th this embodiment of this invention is shown notionally. 4 conceptually shows a noise level detection method in a charge amplifier inspection system according to a fourth embodiment of the present invention. The structure of the sensor system which concerns on 5th Embodiment of this invention is shown. The structure of the communication system which concerns on 6th Embodiment of this invention is shown. The structure of the conventional charge amplifier test | inspection system is shown.

  Embodiments according to the present invention will be described below with reference to the drawings.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 1 shows a configuration of a charge amplifier inspection system 10 according to the first embodiment of the present invention. The charge amplifier inspection system 10 includes a charge amplifier 20 (charge amplification circuit) and a charge supply device 100. Here, in this embodiment, the charge supply device 100 is incorporated in the charge amplifier 20, but the charge supply device 100 may be provided outside the charge amplifier 20.

[Configuration of Charge Amplifier 20]
The charge amplifier 20 amplifies the charge input from the input terminal and outputs an output voltage corresponding to the charge amount from the output terminal. The charge amplifier 20 includes a feedback circuit 22 and an operational amplifier 24. The negative input terminal of the operational amplifier 24 and the input terminal of the feedback circuit 22 are connected in parallel to the input terminal of the charge amplifier 20. An output terminal of the operational amplifier 24 and an output terminal of the feedback circuit 22 are connected in parallel to the output terminal of the charge amplifier 20. The + input terminal of the operational amplifier 24 is grounded to the common ground VCM.

(Feedback circuit 22)
Here, an example of the configuration of the feedback circuit 22 will be described with reference to FIG. FIG. 2 shows a configuration of the feedback circuit 22 provided in the charge amplifier 20 according to the present embodiment. FIG. 2A shows a configuration (first configuration example) of the feedback circuit 22 of the present embodiment. FIG. 2B shows a configuration (second configuration example) of the feedback circuit 22 of the present embodiment.

  The feedback circuit 22 shown in FIG. 2A has a configuration in which a feedback resistor 202 and a feedback capacitor 204 are connected in parallel. The feedback circuit 22 shown in FIG. 2A has a configuration in which a switch 212 and a feedback capacitor 204 are connected in parallel. That is, the feedback circuit 22 shown in FIG. 2A has a configuration in which a switch 212 is provided instead of the feedback resistor 202. As the charge amplifier 20, either the feedback circuit 22 shown in FIG. 2A or the feedback circuit 22 shown in FIG. 2B can be used. Hereinafter, the charge amount of the feedback capacitor 204 is denoted by Cf.

[Configuration of Charge Supply Device 100]
The charge supply device 100 is a device that supplies a charge for inspection to the charge amplifier 20. The charge supply device 100 includes a capacitor 102, a power source 104, a power source 106, a switch 108, and a pulse applicator 110.

(Capacitor 102)
The capacitor 102 has one electrode connected to the output terminal of the switch 108 and the other electrode connected to the input terminal of the charge amplifier 20. Hereinafter, the charge amount of the capacitor 102 is denoted by Ct.

(Power supply 104, Power supply 106)
The power supply 104 is a supply source of the voltage VRM (first voltage). The power source 106 is a supply source of the voltage VRP (second voltage).

(Switch 108)
The switch 108 includes an output terminal, a first input terminal, and a second input terminal. The output terminal is connected to the one electrode of the capacitor 102. The first input terminal is connected to the power source 104. The second input terminal is connected to the power source 106. The switch 108 can selectively switch the input terminal to be electrically connected to the output terminal between the first input terminal and the second input terminal.

  In the charge supply device 100, the first input terminal may be grounded to the ground. In this case, the charge supply device 100 may not be provided with the power source 104. In the charge supply device 100, the second input terminal may be grounded to the common ground VCM. In this case, the charge supply device 100 may not be provided with the power source 106.

(Pulse applicator 110)
The pulse applicator 110 controls the switching between selection of the first input terminal and selection of the second input terminal in the switch 108 by supplying a pulse signal to the switch 108. Specifically, the pulse applicator 110 supplies a pulse signal having a frequency fs at which an ON signal and an OFF signal alternately appear to the switch 108. This frequency fs can be arbitrarily set from the outside.

  When an ON signal is supplied to the switch 108, the selection of the input terminal is switched to the second input terminal, and when the OFF signal is supplied, the selection of the input terminal is switched to the first input terminal. When the switch 108 switches the input terminal selection to the second input terminal, the voltage VRP is applied to the capacitor 102. In addition, when the switch 108 switches the input terminal selection to the first input terminal, the voltage VRM is applied to the capacitor 102.

[Operation of Charge Amplifier Inspection System 10]
Hereinafter, the operation of the charge amplifier inspection system 10 when inspecting the charge amplifier 20 will be described in order.

  (Operation 1) A pulse signal having a frequency fs at which an ON signal and an OFF signal appear alternately is supplied from the pulse applicator 110 to the switch 108.

  (Operation 2) The switch 108 is switched to the second input terminal (input terminal on the voltage VRP side) every time the ON signal is supplied in the above (Operation 1). On the other hand, the switch 108 is switched to the second input terminal (the input terminal on the voltage VRM side) every time the OFF signal is supplied in the above (operation 1).

  (Operation 3) Every time the switch 108 is switched to the second input terminal (the input terminal on the voltage VRP side), the charge Qt obtained by the following equation (4) is supplied from the charge supply device 100 to the charge amplifier 20. The

  For example, when the capacitance Ct of the capacitor 102 is 0.1 pf and (voltage VRP−voltage VRM) is 0.1 V, the charge Qt is 10 fC. From the above formula (4), it can be seen that the charge supply device 100 of the present embodiment can arbitrarily set the charge Qt by adjusting the voltage VRP and the voltage VRM. Further, even if the common-mode noise Vnoise is superimposed on both the voltage VRP and the voltage VRM, the common-mode noise Vnoise is canceled and removed by the above equation (4).

  (Operation 4) In the charge amplifier 20, the charge Qt supplied from the charge supply device 100 is supplied to the feedback capacitor 204 included in the feedback circuit 22, and an output voltage Vo corresponding to the amount of the charge is expressed by the following equation (5). Is output from the output terminal.

  As described above, according to the charge supply device 100 of the present embodiment, it is not necessary to prepare a sensor to be actually used, and a weak current having a desired current value can be easily generated. Further, according to the charge supply device 100 of the present embodiment, the switch 108, the capacitor 102, and the pulse applicator 110 are configured, and since the configuration is simple, the cost associated with the inspection of the charge amplifier 20 is reduced. can do. Further, according to the charge supply device 100 of the present embodiment, since the charge amplifier 20 is built in, the path of the input signal supplied to the charge amplifier 20 can be made relatively short, and therefore, noise is added to the input signal. Can be realized.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a configuration of a charge amplifier inspection system 10 according to the second embodiment of the present invention.

  It is known that the noise gain increases when the parasitic capacitance at the input terminal of the charge amplifier is large. For this reason, it is preferable for the charge amplifier to reduce the parasitic capacitance as much as possible. Therefore, in the charge amplifier inspection system 10 according to the second embodiment, the configuration shown in FIG. 3 is employed in order to make the noise gain less likely to occur during normal operation (non-inspection) of the charge amplifier.

  In the charge amplifier inspection system 10 of the second embodiment shown in FIG. 3, the switch 108 further includes a third input terminal that is floated, and the input terminal that is electrically connected to the output terminal is the first input terminal, It differs from the charge amplifier inspection system 10 of the first embodiment in that it can be selectively switched between the second input terminal and the third input terminal.

  During normal operation (non-inspection) of the charge amplifier, the switch 108 is switched to the third input terminal (the state shown in FIG. 3). As a result, one electrode of the capacitor 102 is in a floating state. As a result, the capacitor 102 cannot move charges, and loses its function as a capacitor. As a result, the charge amplifier inspection system 10 of the present embodiment has a configuration in which noise gain is difficult to occur while the charge supply device 100 is connected to the charge amplifier 20.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 shows the configuration of the charge amplifier inspection system 10 according to the third embodiment of the present invention.

  In the charge amplifier inspection system 10 according to the third embodiment, the configuration shown in FIG. 4 is employed in order to make the noise gain less likely to occur during normal operation (non-inspection) of the charge amplifier.

  The charge amplifier inspection system 10 of the third embodiment is further provided with a switch 112 on the wiring between the capacitor 102 and the charge amplifier 20 that can selectively switch connection and disconnection of the wiring. It differs from the charge amplifier inspection system 10 of the form.

  During normal operation (non-inspection) of the charge amplifier 20, the switch 112 is in an off state (the state shown in FIG. 4). As a result, the charge amplifier inspection system 10 does not reliably transmit the parasitic capacitance of the capacitor 102 to the charge amplifier 20. Thereby, the charge amplifier inspection system 10 of the present embodiment has a configuration in which noise gain is less likely to occur while the charge supply device 100 is connected to the charge amplifier 20.

  When this configuration is adopted, it is preferable to use the switch 112 having a smaller parasitic capacitance than the capacitor 102 in consideration of the parasitic capacitance generated in the switch 112. This is because the effect of reducing the parasitic capacitance input to the charge amplifier 20 can be obtained more reliably than when the switch 112 is not provided.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 5 shows a configuration of a charge amplifier inspection system 10 according to the fourth embodiment of the present invention. The charge amplifier inspection system 10 of the fourth embodiment employs a configuration that can determine the inspection result of the charge amplifier 20.

  The charge amplifier inspection system 10 of the fourth embodiment differs from the charge amplifier inspection system 10 of the first to third embodiments in that it further includes a comparator 130, a DA converter 140, and a control device 150.

(Comparator 130)
The comparator 130 has its − input terminal connected to the output terminal of the charge amplifier 20, and its + input terminal connected to the output terminal of the DA converter 140. The comparator 130 compares the output signal of the charge amplifier 20 with the reference voltage supplied from the DA converter 140, and the comparison result is expressed as a pulse signal (hereinafter referred to as "second pulse signal"). .) Is output. For example, the comparator 130 outputs a second pulse signal in which the portion exceeding the reference voltage in the output signal of the charge amplifier 20 is represented as a pulse (Hi level).

(DA converter 140)
An input terminal of the DA converter 140 is connected to the control device 150. The output terminal of the DA converter 140 is connected to the + input terminal of the comparator 130. A reference voltage set value (digital signal) is input from the control device 150 to the input terminal of the DA converter 140. The DA converter 140 generates a reference voltage corresponding to the input set value, and supplies the generated reference voltage to the comparator 130.

(Control device 150)
The control device 150 includes an input pulse signal control unit 151, a reference voltage level setting unit 152, an output pulse signal acquisition unit 153, a pass / fail determination unit 154, a noise amount detection unit 155, and an amplification amount detection unit 156.

  The input pulse signal control unit 151 controls the pulse applicator 110 to cause the pulse applicator 110 to generate an arbitrary pulse signal (hereinafter referred to as “first pulse signal”), and the generated input pulse. A signal is applied to the switch 108. For example, the input pulse signal control unit 151 sets an arbitrary frequency fs or an arbitrary number of pulses to the pulse applicator 110 to thereby set a pulse signal having an arbitrary frequency fs or a pulse signal having an arbitrary number of pulses. The pulse applicator 110 is controlled to generate.

  The reference voltage level setting unit 152 supplies a reference voltage setting value (digital signal) to the DA converter 140. In response to this, the DA converter 140 generates a reference voltage corresponding to the supplied set value, and the generated reference voltage is supplied to the comparator 130.

  The output pulse signal acquisition unit 153 acquires the pulse signal (second pulse signal) output from the comparator 130.

  The pass / fail determination unit 154 determines the pass / fail of the charge amplifier 20 by comparing the number of pulses included in the first pulse signal with the number of pulses included in the second pulse signal. For example, when the number of pulses of the first pulse signal is “3”, if the peak voltage of all the pulses exceeds the reference voltage, the number of pulses of the second pulse signal is “3”. In this case, the pass / fail determination unit 154 sets the determination of the charge amplifier 20 to “pass”. On the other hand, if the peak voltage of all the pulses does not exceed the reference voltage, the number of pulses of the second pulse signal is “2” or less. In this case, the pass / fail determination unit 154 sets the determination of the charge amplifier 20 as “fail”.

  As described above, the charge amplifier inspection system 10 of the present embodiment determines whether or not an output signal corresponding to the input signal is output, and whether or not the output signal of the charge amplifier 20 is amplified to a desired voltage level. It is possible to judge easily.

  The noise amount detection unit 155 detects the noise level of the noise included in the second pulse signal based on the change in the number of pulses in the second pulse signal that is generated by gradually changing the level of the reference voltage. .

  The amplification amount detection unit 156 detects the signal amplification factor by the charge amplifier 20 based on the change in the number of pulses in the second pulse signal that is generated by gradually changing the level of the reference voltage.

(Signal gain detection method)
Here, with reference to FIG. 6, a method of detecting the signal amplification factor by the control device 150 will be described. FIG. 6 conceptually shows a signal amplification factor detection method in the charge amplifier inspection system 10 according to the fourth embodiment of the present invention.

  For example, the control device 150 detects the signal amplification factor by the charge amplifier 20 according to the following procedure.

  (Procedure 1) The reference voltage level setting unit 152 gradually changes the reference voltage level in a direction approaching the maximum peak level of the output signal.

  (Procedure 2) Each time the level of the reference voltage is changed, the input pulse signal control unit 151 supplies the first pulse signal to the charge amplifier 20, and the output pulse signal acquisition unit 153 supplies the second pulse signal. get. The first pulse signal supplied to the charge amplifier 20 is the same every time.

  (Procedure 3) Every time the second pulse signal is acquired, the amplification amount detector 156 counts the number of pulses included in the second pulse signal.

  (Procedure 4) In the above (Procedure 3), when the count number for a certain second pulse signal is “0”, set when the immediately preceding second pulse signal is obtained by the amplification amount detection unit 156. The reference voltage level thus determined is determined as the maximum peak level in the output signal of the charge amplifier 20.

  (Procedure 5) The amplification amount detection unit 156 calculates the signal amplification factor by the charge amplifier 20 based on the maximum peak level obtained in (Procedure 4) and the voltage level of the first pulse signal.

  For example, in the example illustrated in FIG. 6, the number of pulses obtained by the first to fifth measurements is “2”, “2”, “2”, “1”, and “0” in order. That is, at the time of the fifth measurement, the number of pulses is “0”. In this case, the amplification amount detection unit 156 determines the reference voltage level set when the fourth measurement is performed as the maximum peak level in the output signal of the charge amplifier 20. It is clear from FIG. 6 that the maximum peak level determined in this way is appropriate.

(Noise level detection method)
Here, with reference to FIG. 7, a method of detecting the noise level by the control device 150 will be described. FIG. 7 conceptually shows a noise level detection method in the charge amplifier inspection system 10 according to the fourth embodiment of the present invention.

  For example, the control device 150 detects the noise level in the output signal of the charge amplifier 20 according to the following procedure.

  (Procedure 1) The reference voltage level setting unit 152 gradually changes the reference voltage level in a direction away from the maximum peak level of the output signal.

  (Procedure 2) Each time the level of the reference voltage is changed, the input pulse signal control unit 151 supplies the first pulse signal to the charge amplifier 20, and the output pulse signal acquisition unit 153 supplies the second pulse signal. get. The first pulse signal supplied to the charge amplifier 20 is the same every time.

  (Procedure 3) Each time the second pulse signal is acquired, the noise amount detection unit 155 counts the number of pulses included in the second pulse signal.

  (Procedure 4) In the above (Procedure 3), when the count number for a certain second pulse signal becomes larger than the assumed value (that is, the number of pulses included in the first pulse signal), the noise amount detection unit 155 Thus, the reference voltage level set when the second pulse signal is obtained is determined as the noise level in the output signal of the charge amplifier 20.

  For example, in the example illustrated in FIG. 7, the number of pulses obtained by the first to fifth measurements is “2”, “2”, “2”, “2”, and “10” in order. That is, at the time of the fifth measurement, the number of pulses is larger than the assumed value “2”. In this case, the noise amount detection unit 155 determines the reference voltage level set when the fifth measurement is performed as the noise level in the output signal of the charge amplifier 20. It is clear from FIG. 7 that the noise level obtained in this way is appropriate.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, an example in which the above-described charge amplifier inspection system is applied to a sensor system will be described. FIG. 8 shows a configuration of a sensor system 800 according to the fifth embodiment of the present invention.

  A sensor system 800 illustrated in FIG. 8 includes a sensing device 802, a signal processing circuit 804, a charge supply device 100, and a charge amplifier 20. The sensor system 800 detects a change in a physical quantity of a detection target (for example, acceleration, impact, radiation, light, etc.) by the sensing device 802, amplifies the detection signal by the charge amplifier 20, and based on the amplified detection signal. In this system, predetermined signal processing is performed by a signal processing circuit 804. In the sensor system 800, the charge amplifier 20 is the same as that in the above-described embodiment (first to fourth embodiments). In the sensor system 800, the charge supply device 100 is the same as that in the above-described embodiment (any one of the first to third embodiments).

  Accordingly, the sensor system 800 can easily inspect the charge amplifier 20 by supplying the weak charge from the charge supply device 100 to the charge amplifier 20 without using the sensing device 802. Yes. Of course, since the sensor system 800 does not affect the normal use of the charge supply device 100, it can be used normally with the charge supply device 100 connected. Further, the sensor system 800 can be configured to be able to determine the inspection result of the charge amplifier 20 in combination with the charge amplifier inspection system 10 of the fourth embodiment.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described with reference to FIG. In the sixth embodiment, an example in which the above-described charge amplifier inspection system is applied to a communication system will be described. FIG. 9 shows a configuration of a communication system 900 according to the sixth embodiment of the present invention.

  A communication system 900 illustrated in FIG. 9 includes a transmission device, a communication path 908, and a reception device. The transmission apparatus includes a signal processing circuit 902, a charge amplifier 904, and a transmission device 906. The receiving device includes a receiving device 910, a signal processing circuit 912, a charge supply device 100, and a charge amplifier 20.

  In the transmission device, the signal processing circuit 902 outputs communication data, the communication data is amplified by the charge amplifier 904, and the amplified communication data is transmitted by the transmission device 906. Communication data transmitted from the transmission device is transmitted to the reception device via the communication path 908.

  In the reception device, the reception device 910 receives the communication data, amplifies the communication data by the charge amplifier 20, and performs predetermined signal processing based on the amplified communication data by the signal processing circuit 912.

  In the communication system 900, the same charge amplifier 20 as that in the above-described embodiments (first to fourth embodiments) is used. In the communication system 900, the charge supply device 100 is the same as that in the above-described embodiment (any one of the first to third embodiments).

  Thus, the communication system 900 can easily inspect the charge amplifier 20 by supplying the weak charge from the charge supply device 100 to the charge amplifier 20 without using the receiving device 910. Yes. Of course, since the communication system 900 does not affect the normal use of the charge supply device 100, it can be used normally with the charge supply device 100 connected. Further, the communication system 900 can be configured to be able to determine the inspection result of the charge amplifier 20 in combination with the charge amplifier inspection system 10 of the fourth embodiment.

(Supplementary explanation)
The embodiments according to the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  For example, in the above-described embodiment, at least one of the charge supply device and the charge amplifier may adopt a configuration different from the above-described embodiment. It is included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is applicable to various devices and various systems that employ a configuration that amplifies a weak current using a charge amplifier, and in particular, a weak current output from a sensor for detecting a change in a physical quantity of a target. Can be suitably used for various devices and various systems that employ a configuration in which the charge amplifier is used to amplify the signal.

DESCRIPTION OF SYMBOLS 10 Charge amplifier test | inspection system 20 Charge amplifier 22 Feedback circuit 24 Operational amplifier 100 Charge supply apparatus 102 Capacitor 104 Power supply 106 Power supply 108 Switch (1st switch)
110 Pulse applicator 112 Switch (second switch)
DESCRIPTION OF SYMBOLS 130 Comparator 140 DA converter 150 Control apparatus 151 Input pulse signal control part 152 Reference voltage level setting part 153 Output pulse signal acquisition part 154 Pass / fail judgment part (pass / fail judgment means)
155 Noise amount detection unit (noise level detection means)
156 Amplification amount detection unit (signal amplification factor detection means)
202 feedback resistor 204 feedback capacitor 212 switch 800 sensor system 802 sensing device 804 signal processing circuit 900 communication system 902 signal processing circuit 904 charge amplifier 906 transmission device 908 communication path 910 reception device 912 signal processing circuit

Claims (10)

A charge supply device for supplying a charge for inspection to a charge amplifier,
An input terminal having a first input terminal to which a first voltage is input, a second input terminal to which a second voltage is input, and an output terminal, which is electrically connected to the output terminal, is the first input terminal. A first switch that can be selectively switched between the second input terminal and the second input terminal;
A capacitor having one electrode connected to the output terminal of the first switch and the other electrode connected to an input terminal of the charge amplifier ;
The first switch is
The first input terminal, the second input terminal, and the third input terminal are selectively connected to the first input terminal, the second input terminal, and the third input terminal. A charge supply device that is switchable. The charge supply device according to claim 1 , further comprising: a second switch provided on a wiring between the capacitor and the charge amplifier and capable of selectively switching connection and disconnection of the wiring. . A pulse applicator for controlling selection of the first input terminal and switching between the second input terminals in the first switch by supplying a first pulse signal to the first switch; charge supply device according to claim 1 or 2, characterized in that. A charge supply device according to any one of claims 1 to 3 ,
The charge amplifier, wherein the charge supply device is connected to an input terminal of the charge amplifier. The charge supply device according to claim 3 ,
A charge amplifier inspection system comprising: a comparator that compares an output signal of the charge amplifier with a reference voltage and outputs a second pulse signal in which the comparison result is represented by a pulse. Pass / fail judgment means for judging pass / fail of the charge amplifier by comparing the number of pulses included in the first pulse signal with the number of pulses included in the second pulse signal. The charge amplifier inspection system according to claim 5 . Noise level detection means for detecting a noise level of the second pulse signal based on a change in the second pulse signal caused by gradually changing the level of the reference voltage. The charge amplifier inspection system according to claim 5 or 6 . The apparatus further comprises signal amplification factor detection means for detecting a signal amplification factor by the charge amplifier based on a change in the second pulse signal caused by gradually changing the level of the reference voltage. Item 8. The charge amplifier inspection system according to any one of Items 5 to 7 . A sensor,
A charge amplifier for amplifying an output signal from the sensor;
Signal processing means for performing predetermined signal processing based on the output signal amplified by the charge amplifier;
Sensor system, characterized in that connected to said charge amplifier input terminal, and a charge supply device according to any one of claims 1 to 3. Receiving means for receiving a signal transmitted from the outside;
A charge amplifier for amplifying the signal received by the receiving means;
Signal processing means for performing predetermined signal processing based on the signal amplified by the charge amplifier;
Communication system, wherein said charge amplifier connected to the input terminal of it and a charge supply device according to any one of claims 1 to 3.

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