JP2015099030A - Radiation measuring circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation measuring circuit which can perform correction on counting the loss of a pulse system detector and linear processing on a prescribed current range.SOLUTION: A radiation measuring circuit includes a logarithmic transformation circuit 3 which performs logarithmic transformation of a current signal Iin after a pulse signal from a pulse system detector 1 is converted into a current value in accordance with the pulse number to output it as a logarithmic voltage signal Vlog, and a monitor circuit 4 which obtains a linear voltage signal Vlin based on the current signal Iin before logarithmic transformation in the logarithmic transformation circuit 3. The monitor circuit 4 consists of a current mirror circuit 5 which outputs a current with the same value as the current signal Iin without affecting a logarithmic transformation operation of the logarithmic transformation circuit 3 at all and a linear output circuit 6 which outputs a linear voltage signal Vlin corresponding to the output current Iin of the current mirror circuit 5.

Description

  This invention counts down the number of pulses of the pulse detector when the pulse signal output from the pulse detector detecting the radiation is converted into a current value corresponding to the number of pulses and then logarithmically compressed and output. The present invention relates to a radiation measurement circuit that can automatically correct and obtain a linear output based on a current value corresponding to the number of pulses.

  Conventionally, as a radiation measurement circuit for measuring a radiation intensity and the like by detecting a pulse signal output from a pulse detector such as a proportional counter that detects radiation such as neutrons, for example, the one disclosed in Patent Document 1 below was there. In this Patent Document 1, a pulse signal having a pulse number corresponding to the radiation intensity is amplified from a pulse detector by a preamplifier or the like and then input to a frequency / current converter (hereinafter referred to as an F / I converter). The F / I converter converts the current value according to the number of pulses of the pulse signal. Next, there is a configuration in which a current signal from the F / I converter is logarithmically converted and output as a voltage signal by a logarithmic conversion circuit (for example, see Patent Document 1 below).

Here, there is provided a logarithmic conversion circuit, the number of pulses output from the pulse system detector, since with 10 ⁰ cps~10 of about 6 ^cps range wider Thailand Na dynamic range, and signal compression by logarithmic transformation This is because it is necessary to facilitate subsequent signal processing.

  By the way, in the above-mentioned pulse system detector, since it is a mechanism that generates a pulse by utilizing an ionization phenomenon associated with radiation input, a pulse count down occurs in a high count rate region where the number of pulses increases, A phenomenon occurs in which the number of pulses that are actually output from the pulse system detector decreases with respect to the number of pulses that should be generated.

  Therefore, in Patent Document 1 described above, in the logarithmic conversion circuit, a series circuit of a transistor having a logarithmic characteristic and a resistor is connected between the negative polarity terminal and the output terminal of the operational amplifier, thereby counting down pulses. Is corrected to some extent.

  However, the logarithmic conversion circuit having the configuration described in Patent Document 1 is corrected even when the radiation intensity is weak and the pulse detector does not count down. On the other hand, the correction amount is high in a high count rate region where counting down increases. However, there was a limit in correcting the counting down with high accuracy.

  Therefore, the present inventor puts the first transistor on one input end side of the operational amplifier to which the current signal after being converted into a current value corresponding to the number of pulses by the F / I converter is input. A second transistor whose amount of current from the DC power source is controlled by the output of the operational amplifier is connected to the output terminal side of the amplifier, and a resistance to which the output current from both transistors merges is connected to both transistors. A radiation measurement circuit having a logarithmic conversion circuit connected in common is provided (see Patent Document 2 below).

JP-A-6-102355 JP 2009-300293 A

  In the conventional radiation measurement circuit described in Patent Document 2 described above, the logarithmic conversion circuit can ideally correct the counting loss of the pulse detectors, so that an advantage that radiation measurement can be performed with high accuracy can be obtained. Since only a logarithmically compressed signal is obtained by the logarithmic conversion circuit, there is a problem that it is difficult to accurately monitor a change in a specific range of the current value according to the number of pulses.

  That is, in the conventional radiation measurement circuit, the pulse signal output from the pulse detector that detects radiation is converted into a current value corresponding to the number of pulses, and then logarithmically compressed by the logarithmic conversion circuit. The ratio of the change of the signal after logarithmic compression to the change of the current value according to the number is small.

  For this reason, for example, even if monitoring processing such as issuing an alarm when the signal after logarithmic compression exceeds a preset threshold value, after logarithmic compression with respect to the change in the current value according to the number of pulses. Therefore, it is difficult to perform monitor processing with high accuracy.

  The present invention has been made to solve the above-described problems, and can perform correction of counting down with respect to a decrease in the number of pulses from the detector as theoretically, and can affect the logarithmic conversion operation of the logarithmic conversion circuit. An object of the present invention is to provide a radiation measurement circuit that can obtain a linear output for a specific range of current values according to the number of pulses.

The first radiation measurement circuit according to the present invention is a logarithm that outputs the current signal after logarithmically converting the current signal after the pulse signal output from the pulse detector that detects radiation is converted into a current value corresponding to the number of pulses. A conversion circuit, the logarithmic conversion circuit has an operational amplifier, a first transistor is provided on one input end side of the operational amplifier to which the current signal is input, and an output end side of the operational amplifier is provided on the output end side. A second transistor whose amount of current from the DC power supply is controlled by the output of the operational amplifier is connected to each of the transistors, and a resistance to which output currents from the two transistors merge with the first and second transistors. Are configured to be connected in common,
A monitor circuit that obtains a linear output based on the current signal before being logarithmically converted by the logarithmic converter circuit; the monitor circuit outputting a current having the same value as the current signal; and the current mirror circuit A linear output circuit that generates a linear output signal corresponding to the output current of the first current transistor, wherein the current mirror circuit includes a third transistor symmetrically disposed on the first transistor, and the first and second transistors. And the bases of the three transistors are connected to each other, and a buffer circuit is provided for holding the output voltages of the first and third transistors equal to each other. The linear output circuit is included in the third transistor. It is characterized by being connected.

The second radiation measurement circuit according to the present invention logarithmically converts and outputs the current signal after the pulse signal output from the pulse detector for detecting radiation is converted into a current value corresponding to the number of pulses. The logarithmic conversion circuit has an operational amplifier, and a first transistor into which a current from a DC power source flows is provided on one input end side of the operational amplifier to which the current signal is input. A second transistor whose amount of current from the DC power source is controlled by the output of the operational amplifier is connected to the output terminal side of the operational amplifier, and the first and second transistors and the DC power source are connected to each other. While being configured with a common resistor connected between
A monitor circuit that obtains a linear output based on the current signal before being logarithmically converted by the logarithmic converter circuit; the monitor circuit outputting a current having the same value as the current signal; and the current mirror circuit And a linear output circuit that generates a linear output signal corresponding to the output current of the current mirror circuit. The current mirror circuit includes a first transistor and a third transistor arranged symmetrically with the first transistor. The bases of the transistors are connected to each other, and a buffer circuit is provided for holding the output voltages of the first and third transistors equal to each other. The linear output circuit is connected to the third transistor. It is characterized by being.

  According to the present invention, the correction for counting down the pulse detector can be performed as ideal by the logarithmic conversion circuit, so that radiation measurement can be performed with high accuracy. In addition, since the monitor circuit can obtain a linear output signal for a specific range of the current value according to the number of pulses without affecting the logarithmic conversion operation of the logarithmic conversion circuit, the current value according to the number of pulses can be obtained. The change of the linear output signal with respect to the change can be sufficiently grasped. Therefore, when the value of the linear output signal exceeds a preset threshold value, it is possible to appropriately perform monitoring processing such as issuing an alarm.

It is a block diagram which shows the radiation measurement circuit in Embodiment 1 of this invention. In the radiation measurement circuit of FIG. 1, the number of pulses obtained by the pulse detector and the logarithmic output signal obtained by logarithmically converting the current signal Iin after being converted into a current value corresponding to the number of pulses by the logarithmic conversion circuit. It is a characteristic view which shows the relationship with Vlog. In the radiation measurement circuit of FIG. 1, the number of pulses obtained by the pulse detector and the linear output signal Vlin obtained by the monitor circuit based on the current signal Iin after being converted into a current value corresponding to the number of pulses. It is a characteristic view which shows a relationship. It is a block diagram which shows the radiation measurement circuit in Embodiment 2 of this invention. It is a block diagram which shows the radiation measurement circuit in Embodiment 3 of this invention. It is a block diagram which shows the radiation measurement circuit in Embodiment 4 of this invention.

Embodiment 1 FIG.
1 is a block diagram showing a radiation measurement circuit according to Embodiment 1 of the present invention.

  The radiation measurement circuit according to the first embodiment includes a pulse detector 1 such as a proportional counter for detecting radiation, and a pulse signal having a pulse number corresponding to the radiation intensity from the pulse detector 1 according to the pulse number. F / I converter 2 for converting to current signal Iin having a current value, logarithmic conversion circuit 3 for logarithmically converting current signal Iin output from F / I converter 2 to generate logarithmic output signal Vlog, and logarithm A monitor circuit 4 that generates a linear output signal Vlin based on the current signal Iin before logarithmic conversion by the conversion circuit 3 is provided.

  The logarithmic conversion circuit 3 includes an operational amplifier 30, NPN-type first and second transistors 31 and 32, and a resistor 33. The collector of the first transistor 31 is connected to one input terminal side (negative polarity terminal) of the operational amplifier 30 to which the current signal Iin from the F / I converter 2 is input. The other input terminal side (positive terminal) of the operational amplifier 30 is grounded, and the base of the second transistor 32 is connected to the output terminal side (output terminal) of the operational amplifier 30. One end of a resistor 33 is commonly connected to the emitters of the first and second transistors 31 and 32, and a negative electrode (−V 1) of a DC power supply is connected to the other end of the resistor 33. Further, the base of the first transistor 31 is connected to the base of an NPN-type third transistor 51 for constituting a current mirror circuit 5 to be described later, and the collector of the second transistor 32 is connected to a direct current. The positive electrode (+ V1) of the power supply is connected.

  The monitor circuit 4 does not affect the operation when the logarithmic conversion circuit 3 logarithmically converts the current signal Iin to obtain the logarithmic output signal Vlog, and the monitor circuit 4 does not affect the linear output signal based on the current signal Iin. In order to generate Vlin, a current mirror circuit 5 that outputs a current having the same value as the current signal Iin and a linear output circuit 6 that generates a linear output signal Vlin corresponding to the output current Iin of the current mirror circuit 5 are provided. ing.

  In the current mirror circuit 5, an NPN-type third transistor 51 is arranged symmetrically to the NPN-type first transistor 31. The bases of the first and third transistors 31 and 32 are connected to each other, and the connection point is grounded. The collector and base of the third transistor 51 are connected. Further, an operational amplifier for holding the emitter voltages of the first and third transistors 31 and 51 the same so that the currents flowing from the collectors to the emitters of the first and third transistors 31 and 51 are equal to each other. A buffer circuit 52 is provided.

  The emitter of the first transistor 31 is connected to one input end side (positive terminal) of the buffer circuit 52, and the emitter of the third transistor 51 is connected to the other input end side (negative terminal). Yes. The output terminal of the buffer circuit 52 is connected to the emitter of the third transistor 51.

  The linear output circuit 6 includes an inverting amplifier including an operational amplifier 60 and a feedback resistor 61. The collector of the third transistor 51 constituting the current mirror circuit 5 is connected to one input end side (negative polarity terminal) of the operational amplifier 60, and the other input end side (positive polarity terminal) is grounded. A linear output signal Vlin corresponding to the output current Iin of the current mirror circuit 5 is output from the output terminal of the operational amplifier 60.

  In the above configuration, the pulse signal output from the pulse detector 1 is converted into a current value corresponding to the number of pulses by the next stage F / I converter 2 and output as a current signal Iin. Next, the logarithmic conversion circuit 3 performs logarithmic conversion on the current signal Iin and outputs it as a logarithmic output signal Vlog.

  In this case, paying attention to the logarithmic conversion circuit 3, the current signal Iin from the F / I converter 2 is input to the negative terminal (−) of the operational amplifier 30, and via the first transistor 31 and the resistor 33. It flows to the negative electrode side (-V) of the DC power supply. As a result, when a potential difference occurs between both input terminals of the operational amplifier 30, the operational amplifier 30 outputs a logarithmic output signal Vlog corresponding to the potential difference. Then, the current of the second transistor 32 is controlled by the logarithmic output signal Vlog output from the operational amplifier 30, and the negative polarity of the DC power supply (+ V1) from the positive polarity (+ V1) of the DC power supply through the second transistor 32 and the resistor 33. Current flows through -V1).

Here, if the current flowing through the resistor 33 is If, the current signal output from the F / I converter 2 is Iin, and the current flowing from the collector of the second transistor 32 to the emitter is Ic, then Ic = If−Iin Yes, if the logarithmic output signal output from the logarithmic conversion circuit 3 is Vlog and ln is a natural logarithm due to the logarithmic characteristics of the first and second transistors 31 and 32,
Vlog =-[ln (Iin) -ln (Ic)]
=-[Ln (Iin) -ln (If-Iin)]
= -Ln {Iin / (If-Iin)} (1)
It becomes.

On the other hand, it is generally known that the count correction formula in the pulse detector 1 is given by the following formula.
N = Nx / (1−Nx · τ) (2)
Here, N is the number of pulses corrected to be counted down, Nx is the number of pulses detected by the pulse detector 1, and τ is the resolution of the pulse detector 1.

Taking the logarithm of both sides of equation (2),
ln (N) = ln {Nx / (1-Nx · τ)}
= Ln [Nx / {τ · (1 / τ−Nx)}]
= Ln {Nx / (1 / τ-Nx)}-ln (τ) (3)
It becomes.

  Comparing the first term on the right side of the above equation (1) with the first term on the right side of the equation (3), if Iin = Nx and If = 1 / τ, the difference between the positive and negative polarities is It becomes equivalent. The current signal Iin output from the F / I converter 2 corresponds to the number of pulses Nx detected by the pulse detector 1, and the current If flowing through the resistor 33 corresponds to 1 / τ. Thus, it is possible to adjust the resistance value and the voltage of the negative electrode (−V1) of the DC power supply. Further, ln (τ) in the second term on the right side of the above equation (3) does not depend on the change in the radiation intensity, and is a constant value having a value specific to the pulse detector 1. It is possible to add signals to the obtained logarithmic output signal Vlog by an amount corresponding to ln (τ) by a subsequent arithmetic processing circuit (not shown).

  Therefore, when the radiation intensity (counting rate) is finally obtained by calculation processing based on the logarithmic output signal Vlog obtained by the logarithmic conversion circuit 3, the ideal counting correction relationship can be maintained, and the counting down is performed. Can be corrected with high accuracy.

  On the other hand, when the current signal Iin output from the F / I converter 2 flows through the first transistor 31 and the resistor 33 to the negative side (−V) of the DC power supply, the buffer circuit 52 constituting the current mirror circuit 5 Since the emitter voltages of the first and third transistors 31 and 51 are held at the same value, the magnitude of the current flowing from the collector of the third transistor 51 to the emitter is from the collector of the first transistor 31 to the emitter. It becomes equal to the current value of the flowing current signal Iin.

  The current signal Iin flowing through the third transistor 51 is inverted and amplified by the operational amplifier 60 of the linear output circuit 6 and output as the linear output signal Vlin. In this case, the current range when the linear output signal Vlin is generated based on the current signal Iin is set by adjusting the gain of the operational amplifier 60.

As shown in FIG. 2, a logarithmic output signal Vlog obtained by logarithmically converting the current signal Iin by the logarithmic conversion circuit 3 with respect to the current signal Iin corresponding to the number of pulses (cps: count per second) is logarithmically compressed. For example, when the number of pulses changes in the range of 10 ² to 10 ³ , the change amount of the logarithmic output signal Vlog is relatively small at 1.667V. For this reason, even if it is attempted to monitor the change in the logarithmic output signal Vlog, it is difficult to perform the monitor process with high accuracy because the amount of change is small.

On the other hand, as shown in FIG. 3, for example, when the number of pulses (cps) changes in the range of 10 ² to 10 ³ , the change amount of the linear output signal Vlin obtained by the monitor circuit 4 is relatively 9V. It is large and can fully grasp the amount of change. Therefore, when the value of the linear output signal Vlin exceeds a preset threshold value, it is possible to appropriately perform monitoring processing such as issuing an alarm.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing a radiation measurement circuit according to the second embodiment of the present invention, and the same reference numerals are given to the components corresponding to those in the first embodiment shown in FIG.

The feature of the second embodiment is that, in the logarithmic conversion circuit 3, an NPN-type fourth transistor 34 is connected in series to the resistor 33 at a position between the first and second transistors 31 and 32 and the resistor 33. Thus, a constant current circuit is configured. That is, the collector of the fourth transistor 34 is commonly connected to the emitters of the first and second transistors 31 and 32, the emitter is connected to the resistor 33, and the base is connected to the positive electrode (+ V2) of the DC power supply. It is connected.
Since other configurations are the same as those of the first embodiment, detailed description thereof is omitted here.

In maintaining the ideal counting correction relationship, as can be seen from the correspondence between the first term on the right side of equation (1) and the first term on the right side of equation (3), the current flowing through the resistor 33 It is preferable that If is always stabilized. Therefore, by connecting the third transistor 34 to the resistor 33 in series, the current If that always flows can be stabilized. Thereby, compared with the case of the first embodiment, although the number of transistors is slightly increased, the count-down correction can be performed with higher accuracy.
Since the operation of the monitor circuit 4 is the same as that of the first embodiment, detailed description thereof is omitted here.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing a radiation measurement circuit according to the third embodiment of the present invention. Components corresponding to those in the first embodiment shown in FIG.

  In the first and second embodiments, the current signal Iin input to the logarithmic conversion circuit 3 is positive. In the third embodiment, the current signal Iin input to the logarithmic conversion circuit 3 is negative. It is designed to handle the case of sex.

  That is, in the third embodiment, the logarithmic conversion circuit 3 includes an operational amplifier 30, PNP-type first and second transistors 36 and 37, and a resistor 38. The collector of the first transistor 36 is connected to one input terminal side (negative polarity terminal) of the operational amplifier 30 to which the current signal Iin from the F / I converter 2 is input. The other input end side (positive terminal) of the operational amplifier 30 is grounded, and the base of the second transistor 37 is connected to the output end side (output terminal) of the operational amplifier 30. Further, one end of a resistor 38 is commonly connected to the emitters of the first and second transistors 36 and 37, and a positive electrode (+ V3) of a DC power source is connected to the other end of the resistor 38. Further, the base of the first transistor 36 is connected to the base of a PNP-type third transistor 56 for constituting the current mirror circuit 5, and the collector of the second transistor 37 is connected to a DC power source. The negative electrode (-V3) is connected.

  The monitor circuit 4 does not affect the operation when the logarithmic conversion circuit 3 logarithmically converts the current signal Iin to generate the logarithmic output signal Vlog, and the monitor circuit 4 performs linear output based on the current signal Iin. In order to obtain the signal Vlin, a current mirror circuit 5 that outputs a current having the same value as the current signal Iin and a linear output circuit 6 that generates a linear output signal Vlin corresponding to the output current Iin of the current mirror circuit 5 are provided. ing.

  In the current mirror circuit 5, a PNP-type third transistor 56 is arranged symmetrically to the PNP-type first transistor 36. The bases of the first and third transistors 36 and 56 are connected to each other, and the collector and base of the third transistor 56 are connected to each other. Further, an operational amplifier for maintaining the collector voltages of the first and third transistors 36 and 56 equal to each other so that the currents flowing from the emitters to the collectors of the first and third transistors 36 and 56 are equal to each other. A buffer circuit 52 is provided.

  The collector of the first transistor 36 is connected to one input end side (positive terminal) of the buffer circuit 52, and the collector of the third transistor 56 is connected to the other input end side (negative polarity terminal). Further, the output terminal of the buffer circuit 52 is connected to the collector of the third transistor 56.

  The linear output circuit 6 includes an inverting amplifier including an operational amplifier 60 and a feedback resistor 61. The emitter of the third transistor 56 constituting the current mirror circuit 5 is connected to one input end side (negative polarity terminal) of the operational amplifier 60, and the other input end side (positive polarity terminal) is grounded. A linear output signal Vlin corresponding to the output current Iin of the current mirror circuit 5 is generated from the output terminal of the operational amplifier 60.

  Also in the case of the third embodiment, the current flowing through the resistor 38 is If, the current signal output from the F / I converter 2 is Iin, the current flowing through the second transistor 37 is Ic, and the logarithmic conversion circuit 3 When the logarithmic output signal to be output is Vlog, the above-described equation (1) is obtained.

  Therefore, also in the case of the third embodiment, as in the case of the first and second embodiments, the radiation intensity (counting rate) is finally obtained by calculation processing based on the logarithmic output signal Vlog obtained by the logarithmic conversion circuit 3. When it is obtained, the ideal counting correction relationship can be maintained, and counting can be corrected with high accuracy.

  Further, as in the case of the first and second embodiments, the monitor circuit 4 outputs a linear output signal Vlin corresponding to the output current Iin output from the F / I converter 2, so that the linear output signal Vlin The amount of change can be fully understood. Therefore, when the value of the linear output signal Vlin exceeds a preset threshold value, it is possible to appropriately perform monitoring processing such as issuing an alarm.

Embodiment 4 FIG.
FIG. 6 is a block diagram showing a radiation measurement circuit according to the fourth embodiment of the present invention, and the same reference numerals are given to the components corresponding to those of the third embodiment shown in FIG.

The feature of the fourth embodiment is that in the logarithmic conversion circuit 3, a PNP-type fourth transistor 39 is connected in series to the resistor 38 at a position between the first and second transistors 36 and 37 and the resistor 38. Thus, a constant current circuit is configured. That is, the collector of the fourth transistor 39 is commonly connected to the emitters of the first and second transistors 36 and 37, the emitter is connected to the resistor 38, and the base is the negative electrode (−V4) of the DC power supply. )It is connected to the.
Since other configurations are the same as those of the third embodiment, detailed description thereof is omitted here.

Also in the fourth embodiment, by connecting the fourth transistor 39 in series with the resistor 38, the current If flowing through the resistor 38 can always be stabilized. As a result, the ideal count-down correction relationship can be maintained, and the count-down correction can be performed more accurately although the number of transistors is slightly increased as compared with the third embodiment. .
Since the operation of the monitor circuit 4 is the same as that of the third embodiment, a detailed description is omitted here.

  The present invention is not limited to the configuration of each of the first to fourth embodiments described above, and modifications may be made to the configuration or the configuration may be omitted without departing from the spirit of the present invention. In addition, the configurations of the first to fourth embodiments can be appropriately combined as necessary.

1 pulse system detector, 2 F / I converter, 3 logarithmic conversion circuit, 4 monitor circuit,
5 current mirror circuit, 6 linear output circuit, 30 operational amplifier,
31, 36 first transistor, 32, 37 second transistor,
33, 38 resistor, 51, 56 third transistor, 52 buffer circuit,
60 operational amplifier, 34, 39 fourth transistor.

Claims (3)

A logarithmic conversion circuit for logarithmically converting and outputting a current signal after a pulse signal output from a pulse detector that detects radiation is converted into a current value corresponding to the number of pulses is provided. A first transistor is provided on one input end side to which the current signal of the operational amplifier is input, and an amount of current from a DC power source is output from the operational amplifier on the output end side of the operational amplifier. Are connected to each other, and the first and second transistors are connected in common with a resistor to which output currents from the two transistors are combined,
A monitor circuit that obtains a linear output based on the current signal before being logarithmically converted by the logarithmic converter circuit; the monitor circuit outputting a current having the same value as the current signal; and the current mirror circuit A linear output circuit that generates a linear output signal corresponding to the output current of the first current transistor, wherein the current mirror circuit includes a third transistor symmetrically disposed on the first transistor, and the first and second transistors. And the bases of the three transistors are connected to each other, and a buffer circuit is provided for holding the output voltages of the first and third transistors equal to each other. The linear output circuit is included in the third transistor. A radiation measurement circuit characterized by being connected. A logarithmic conversion circuit for logarithmically converting and outputting a current signal after a pulse signal output from a pulse detector that detects radiation is converted into a current value corresponding to the number of pulses is provided. A first transistor into which a current from a DC power source flows into one input end side to which the current signal of the operational amplifier is input; and an output end side of the operational amplifier at the output end side of the operational amplifier. A second transistor whose amount of current from the DC power supply is controlled by an output is connected to each other, and a resistor is commonly connected between the first and second transistors and the DC power supply. on the other hand,
A monitor circuit that obtains a linear output based on the current signal before being logarithmically converted by the logarithmic converter circuit; the monitor circuit outputting a current having the same value as the current signal; and the current mirror circuit And a linear output circuit that generates a linear output signal corresponding to the output current of the current mirror circuit. The current mirror circuit includes a first transistor and a third transistor arranged symmetrically with the first transistor. The bases of the transistors are connected to each other, and a buffer circuit is provided for holding the output voltages of the first and third transistors equal to each other. The linear output circuit is connected to the third transistor. Radiation measurement circuit characterized by being made. The radiation measuring circuit according to claim 1, wherein a transistor is connected in series to the resistor to form a constant current circuit.

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