JPH02134591A - Gated integrator - Google Patents

Abstract

PURPOSE:To miniaturize an apparatus by constituting an integrated circuit of the first and second operational amplifiers, a switching means, a driver for driving the same and the first - fifth terminals and connecting an integrating condenser between the first and second terminals. CONSTITUTION:A signal for controlling a switch 13 is applied to a terminal 14a and subjected to ON/OFF control through a driver 14. When the switch is in an OFF-state, said switch is turned OFF only for the time (t) before and after an input pulse current iin is inputted and this pulse current iin is accumulated in a condenser 15 and the integration result of the input current iin is outputted to output voltage Vo. When the switch 13 is in an ON-state, a feedback circuit composed of operational amplifiers 11, 12 is formed and the voltage Vo coincides with the reference voltage Vr. That is, when the open loop gain of the operational amplifier 2 is sufficiently large, the current iin lowing in the operational amplifier 11 is compressed and not issued as output voltage. After all, during the ON-state of the switch 13, arbitrary voltage can be outputted regardless of the current iin.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a gated integrator used in radiation measuring instruments, etc. In particular, it outputs any desired voltage while not performing integration, and the circuit configuration is simplified. This invention relates to a gated integrator that does not require adjustment or adjustment, and can also perform temperature compensation.

"Prior Art" As is well known, the occurrence of radiation is irregular and stochastic. To measure radiation with such properties,
Converts radiation generated in pulses into pulse signals,
Furthermore, only one pulse signal is captured and integrated to measure the radiation energy. A gated integrator is used to capture only one pulse signal in this way.

FIG. 4 is an electrical circuit diagram showing an example of a conventional gated integrator. That is, a parallel circuit including an integrating capacitor 102 and an on/off control switch 103 is inserted between the input end and the output end of the operational amplifier 101. A pulsed current obtained by converting pulsed radiation into a current is input to the input terminal of the operational amplifier 101.
This pulse current is integrated into the capacitor 102 when the switch 103 is off (open).

Note that the switch 103 is provided, for example, in a pile-up rejector (a circuit for rejecting the manual force of subsequent pulses) of a radiation measuring instrument, and gates the single pulse current to be measured for a time t. (See Figure 3(a)).

Now, as the switch 103 of the conventional gated integrator shown in FIG. 4, it is common to actually use an FET (field effect transistor). FIG. 5 specifically shows this, and a control circuit 104 for controlling switching is connected to the FET 103A and its gate.

By the way, a capacitor exists inside this FET 103A. Therefore, the pulse signal of the control circuit 104 is
There is a problem that it leaks into the switch circuit of T103A. This is called a pedestal, and is a problem that always occurs when FETs are used as switches. This is the 6th
Figure (a).

This will be further explained by (b).

That is, the signal waveform of an ideal switch is as shown in FIG. 6(a), and when a human pulse signal is applied between gate pulses, an integrated output signal is obtained.

However, as shown in FIG. 6(b), the pedestal indicated by symbol A generates switch noise indicated by symbol B, and the waveform differs from the ideal one. Therefore,
For example, a phenomenon occurs in which a subsequent pulse detection circuit (not shown) considers this noise to be a signal, causing distortion in the energy spectrum.

One way to solve this problem is to cancel the pedestal component by inserting a capacitor of small capacity (pF order) on the output side of the control circuit 104, for example.

In addition, as shown in FIG. 7, in order to make the output voltage when the switch 103 is on (closed state) an "arbitrary output voltage", the positive input terminal (10) of the operational amplifier 101 must be This can be realized by applying an input voltage vr'' (imaginary short).

Further, the output voltage when the switch 103 is off is the integral voltage of the human power pulse current. That is, in the circuit configuration shown in FIG. 7, when the switch 103 is turned on, the output voltage v0 can be made equal to the arbitrary voltage V applied to the positive input terminal.

However, an actual gated integrator is generally used with a circuit configuration as shown in FIG.

That is, the output voltage V of the previous stage (not shown) is connected to the resistor 10
5 to convert it into current.

Here, FIG. 7 and FIG. 8 will be compared. In the case of FIG. 7, the arbitrary input voltage v, and input current l are independent of each other, and as described above, when the switch 103 is on due to the imaginary short, the output voltage is V. always matches input terminal ■.

However, in the case of FIG. 8, the input terminals to the operational amplifier 101 are the input voltage v, and the arbitrary input terminal v.

Since it depends on the voltage difference between V and V, the integration result depends on the value of an arbitrary input terminal V. As a result, there is a problem in that the integration result (output voltage v0) varies depending on the value of an arbitrary input terminal vr.

“Problems to be Solved by the Invention” As mentioned above, in conventional gated integrators, trying to solve the pedestal requires complicated circuits, and the output voltage when the switch is on is set to “any voltage”. Furthermore, it is difficult to set the temperature compensation to 100%, and furthermore, there are problems in that the patent path featuring temperature compensation becomes complicated.

An object of the present invention is to provide a gated integrator that solves the above-mentioned problems.

Means for Solving the Problems The present invention has one input end connected to a first terminal to which external parts etc. can be attached, the other input end grounded, and the output end connected to an external part etc. A first operational amplifier connected to a second attachable terminal, and a third and fourth operational amplifier whose one input terminal and the other input terminal are respectively attachable to external components, etc.
an integrated circuit comprising: a second operational amplifier connected to a terminal of the second operational amplifier; and switching means that can be turned on and off and provided between an output terminal of the second operational amplifier and one input terminal of the first operational amplifier. an integrating capacitor connected between the first terminal and the second terminal of the first operational amplifier;
means for supplying a pulse current such as radiation to a first terminal of an operational amplifier;
means for connecting the second operational amplifier to a third terminal of the second operational amplifier; and means for supplying a reference voltage to the fourth terminal of the second operational amplifier;
a fifth supplying an on/off control signal to the switching means;
The gated integrator is equipped with terminals.

In this way, a gated integrator can be realized with a simple component configuration, and the switch is in the OFF state.
When , any set voltage can be output, and “
When in the OFF state, the integrated value of the input terminal from the moment the switch is turned off can be output.

"Example" Next, the present invention will be explained based on illustrated embodiments.

FIG. 1 is an electric circuit diagram showing the overall configuration of an embodiment of a gated integrator of the present invention, and FIG. 2 is an internal configuration diagram of an integrated circuit used in this embodiment.

As shown in the figure, the integrated circuit 10 includes first and second operational amplifiers 11 and 12, a switching means 13, a driver 14 for driving the switching means 13, and first to fifth terminals 11a, llb, 12.
a, 12b, and 14a. An example of an integrated circuit with such a configuration is SHM-
There are 6° SHM-20, etc., which are used for sampling and holding.

An integrating capacitor 15 is connected between the first terminal 11a and the second terminal 11b of the first operational amplifier 11. An input terminal 16 is connected to a connection point between the first terminal 11a and the capacitor 15 to which a pulse current such as radiation is applied.

The second terminal 11b is connected to the third terminal 12a of the second operational amplifier 12, forming a feedback circuit.

A fourth terminal 12b of the second operational amplifier 12 is connected to a terminal 17 that supplies a reference voltage that is the base of the output.

A control signal for on/off controlling the switching means 13 is applied to the fifth terminal 14a, and controlling the switching means 13 on/off via the driver 14.

Next, the operation of the gated integrator configured as described above will be explained with reference to an operation waveform diagram shown in FIG.

When the switching means 13 is in the off state, the input current 1. Otherwise, the input current is accumulated in the capacitor 15, and the integration result of the input current is output as the output voltage v0. That is, in the figure, the time t before and after the first input pulse current 3a is applied manually
The switch 13 is turned off only during this period, the first input pulse current 3a is accumulated in the capacitor 15, and the first output voltage 4a is output.

Further, when the switch 13 is in the on state, the first and second
A feed bank circuit is formed by operational amplifiers 11 and 12, and the output voltage matches an arbitrary reference voltage V. That is, when the open loop gain of the second operational amplifier 12 is sufficiently large, the input terminal (for example, the second pulse current 3b) flowing into the first operational amplifier 11 is compressed and does not come out as an output voltage.

In other words, while the switching means 13 is in the on state, any reference voltage v,
It becomes possible to output.

Similarly, when the third pulse current 3C arrives, the switching means 13 is turned off, so that the integrated output voltage 4C is output.

In this way, according to this embodiment, the gated integrator is configured using commercially available integrated circuits, so the control circuit for the switching means is simple, the problem regarding the pedestal has been solved in advance, and the pedestal Compensation of temperature characteristics due to correction is also resolved. Therefore, it is possible to reduce the size and cost, and there is no need to worry about changes in the circuit due to aging.

Although this embodiment shows the case where the arbitrary reference voltage vr gradually increases, it goes without saying that it may also exhibit a constant value or decrease.

"Effects of the Invention" As explained above, according to the present invention, the control circuit for the switching means is simplified, the problem with the pedestal has been solved in advance, and the compensation of temperature characteristics caused by pedestal correction has also been solved. There is.

Therefore, it is possible to downsize and reduce costs, and there is no need to worry about circuit fluctuations due to aging.

Further, while integration is not being performed, it is possible to match the output voltage to an arbitrary input terminal and output it, and it is also possible to obtain an integration result (output voltage) based on this arbitrary voltage.

[Brief explanation of the drawing]

1 to 3 are diagrams each explaining a gated integrator according to an embodiment of the present invention, in which FIG. 1 is an electric circuit diagram of the overall configuration, and FIG. 2 is an electric circuit diagram of an integrated circuit used as a component. Figures 3 and 3 are operational waveform diagrams, Figures 4 to 8 are diagrams explaining conventional gated integrators, respectively, with Figure 4 being a principle diagram, and Figure 5 being a specific electrical circuit diagram. Figures 6 (a) and (b) are diagrams showing the ideal output signal and the case where it is affected by the actual pedestal, Figure 7 is the diagram showing the case where a current is manually applied to the negative input terminal of the operational amplifier, FIG. 8 is a diagram showing a case where when a voltage is applied to the negative input terminal of an operational amplifier, it is converted into a current and supplied. 3a, 3b, 3c...Manual pulse current, 4a,
4b... Output voltage, 10... Integrated circuit, 11... First operational amplifier (operational amplifier),
11a...first terminal, llb...second terminal, 12a...third terminal, 12b...
...Fourth terminal, 14a...Fifth terminal, 12...Second operational amplifier (operational amplifier), 1
3... Switching means, 15... Integrating capacitor, 16.17.18... Input terminal. Applicant Japan Atomic Energy Corporation Representative Patent Attorney Umeo Yamauchi 1st 20th 6th (A) (Japanese)

Claims (1)

[Claims] One input end is connected to a first terminal to which external parts etc. can be attached, the other input terminal is grounded, and the output terminal is connected to a second terminal to which external parts etc. can be attached. a first operational amplifier connected to the terminal; a second operational amplifier, one input end and the other input end connected to third and fourth terminals to which external components etc. can be attached, respectively; an integrated circuit having switching means that can be turned on and off and provided between the output terminal of the second operational amplifier and the one input terminal of the first operational amplifier; and a first terminal of the first operational amplifier. an integrating capacitor connected between the first operational amplifier and a second terminal; means for supplying a pulsed current such as radiation to the first terminal of the first operational amplifier; and a second terminal of the first operational amplifier. and a third terminal of the second operational amplifier; means for supplying a reference voltage to the fourth terminal of the second operational amplifier; and a fifth circuit for supplying an on/off control signal to the switching means. A gated integrator characterized by having a terminal.