JP3131473B2 - Infrared light detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared light detecting device, and more particularly, to an infrared light detecting device capable of amplifying a signal with extremely low noise.

[0002]

2. Description of the Related Art Time-resolved spectroscopy is effectively used to observe spectra of short-lived molecular species.
Conventionally, it has been mainly performed using light in the ultraviolet to visible range. However, recently, an infrared light source having a high luminance and an infrared light detector having a high sensitivity and an excellent time response have been developed, and thus, the use of infrared light has been increasing.

In the case of observing spectra of molecular species and the like by time-resolved infrared spectroscopy, usually, for example, a glow bar or a laser is used as an infrared light source, and MCT (mercury-cadmium-tellurium) is used as an infrared light detector. ) Detector and I
An nSb (indium-antimony) detector is used. An appropriate DC bias voltage is applied to the infrared light detector. The electrical signals obtained by these infrared light detectors are
After being amplified by the amplifier, it is input to an electric gate circuit, where a time-resolved signal is extracted. As the electrical gate circuit, a boxcar integrator, a digital oscilloscope (DSA), or the like is usually used.

In this type of electronic measurement, the signal from the detector is often weak, and it is required to amplify the signal with low noise and high stability. 7 and 8
FIG. 1 shows a conventional amplifier used for this kind of measurement.

FIG. 7 is a circuit diagram showing an example of a circuit configuration of a conventional amplifier used for this kind of measurement. This conventional amplifier 51 is a two-stage amplifier including a first amplifier and a second amplifier.

[0006] The first amplifying unit is configured by connecting n identical feedback amplifier circuits in parallel. A1 to An are operational amplifiers, RF1 to RFn and RS1 to RSn are feedback resistors, R1 to Rn
Is a resistor for combining the outputs of the operational amplifiers A1 to An. The input of each amplifier circuit is common, and the input signal is input to the operational amplifiers A1 to An from its + terminal. Operational amplifier A1
The negative terminals of .about.An are grounded via feedback resistors RS1 to RSn. Some of the outputs of the operational amplifiers A1 to An are fed back to the minus terminals of the operational amplifiers A1 to An via feedback resistors RF1 to RFn. The output of each amplifier circuit is a resistor R1 to Rn.
Via retrieved, that Re <br/> transmitted after being synthesized in the second amplifier. Here, all n feedback amplifier circuits are non-inverted.
It is configured as an amplifier.

[0007] The second amplifying section comprises one feedback amplifier circuit having an operational amplifier Aa and a feedback resistor RFa. The output obtained by combining the outputs of the n amplifier circuits of the first amplifier is input to the operational amplifier Aa from its minus terminal. The + terminal of the operational amplifier Aa is grounded. Operational amplifier Aa
Of the output of the operational amplifier Aa via the feedback resistor RFa.
Is fed back to the negative terminal. Here, the feedback amplifier circuit is inverted
It is configured as an amplifier.

In the above-described conventional amplifier 51, when a signal is input from the input terminal, the signal is input to n feedback amplifier circuits of the first amplifier and amplified. The outputs of these amplifier circuits are taken out via resistors R1 to Rn, combined, and input to the operational amplifier Aa of the second amplifier. The signal input to the operational amplifier Aa is amplified and sent to an output terminal.

In the first amplifying section, n same feedback amplifier circuits
Are connected in parallel, so that the signal is output from the first amplification unit.
The signal component of the combined output current of each feedback amplifier circuit is
It has n times the signal component of the output of the width circuit alone. other
On the other hand, the noise components of the output of each feedback amplification circuit are random and mutually
Of the combined output current of each feedback amplifier circuit.
The noise component is n ^1/2 of the noise of the output of each feedback amplifier circuit alone.
become. Therefore, in the conventional amplifier 51, the first
The noise of the combined output of the amplifier is reduced to (1 / n) ^1/2 ,
As a result, S / N is improved. Multiple times cascaded
Circuit, the input impedance of the subsequent circuit is
Generally, it should be higher than the input impedance of the road
However, like the first amplifier of the amplifier 51 in FIG.
By connecting their width in parallel and summing their outputs.
In a circuit configuration that reduces noise,
It is common to make the impedance low enough. In fact, the figure
In the amplifier 51 of No. 7, the feedback amplification circuit of the second amplification unit
Inverting amplifier with low input impedance (ie, current amplification
).

FIG. 8 is a circuit diagram showing an example of a circuit configuration of another conventional amplifier used for this type of measurement.

The conventional amplifier 61 shown in FIG. 8 has a two-stage configuration using two transistors Q1 and Q2 having a common emitter. The signal is input to the base of the first transistor Q1 via the capacitor C1, and the output is
Through the collector of the second-stage transistor Q2. In order to increase the operation stability, a negative feedback is applied from the emitter of the second transistor Q2 to the base of the first transistor Q1 via the feedback resistor RF. RC
Is the collector resistance of the transistor Q1, RE is the emitter resistance of the transistor Q2, and R1 is the collector resistance of the transistor Q2.

Generally, in order to match the input impedance of the amplifier to the signal source resistance (for example, 50Ω), a matching resistor having a resistance equal to the signal source resistance may be connected in parallel to the input terminal of the amplifier. However, in that case, the matching resistor becomes a new noise source, so that the noise increases.
Therefore, it is desired to match the input impedance without using a matching resistor.

This conventional amplifier 61 realizes matching of input impedance equivalently by negative feedback without using a matching resistor as a noise source. This eliminates the need to connect a resistor to the input terminal, thereby enabling low-noise amplification.

The collector resistance RC is, for example, 2.2 k
Ω, the emitter resistance RE is, for example, 200Ω, the collector resistance R1 is, for example, 360Ω, and the feedback resistance RF is, for example, 2.2 k.
Ω, the capacitor C1 is, for example, 2000 pF, and the capacitor C2 is, for example, 10,000 pF.

[0015]

The conventional amplifier 51 described above
Has a direct effect on the noise reduction of each amplifier circuit of the first amplifying unit because the feedback resistors RF1 to RFn and RS1 to Rs
Sn, and it is preferable to set their resistance values as small as possible. However, in the above-mentioned conventional amplifier 51, since the minus terminal of the second amplifying unit is regarded as virtual ground, the operational amplifiers A1 to An are respectively connected to the feedback resistors RF1 to RFn and RS1 to RSn
In addition, it is necessary to drive the resistors R1 to Rn. For this reason, it is difficult to set the resistance values of the feedback resistors RF1 to RFn and RS1 to RSn low, and there is a problem that noise reduction is limited.

On the other hand, the conventional amplifier 61 has a problem that it is difficult to perform highly stable amplification because the gain and the input impedance fluctuate when the ambient temperature fluctuates due to the temperature dependence of the transistors Q1 and Q2. is there.

SUMMARY OF THE INVENTION An object of the present invention is to provide an infrared light detecting device having a simple structure and extremely low noise.

Another object of the present invention is to provide an infrared light detecting device whose operation is extremely stable against a change in ambient temperature.

[0019]

A first infrared light detecting device according to the present invention includes infrared light detecting means for receiving an infrared light and generating an electric signal corresponding thereto, and coupled to the detecting means; Amplifying means for amplifying the electric signal generated by the detecting means, wherein the amplifying means has respective input terminals connected in parallel.
Connected to each other and a resistor connected to each output terminal
And a feedback amplifier circuit of
The output is taken out via the corresponding resistor and synthesized.
Combining one amplifier and outputs of the plurality of feedback amplifier circuits
The obtained output of the first amplifying unit is inputted and the non-inverting amplification circuit is used.
And a second amplifying section having a path configuration.
The signal components of the outputs of the plurality of feedback amplifier circuits of the first amplifier section.
The components are in phase with each other, and the input
Impedance of the plurality of feedback amplifiers of the first amplifying unit.
The parallel resistance of said resistor connected to each output terminal of the circuit
It is characterized in that it is not less than the value .

A second infrared light detecting device according to the present invention includes an infrared light detecting means for receiving an infrared light and generating an electric signal corresponding thereto, and an infrared light detecting means coupled to the detecting means and generated by the detecting means. Amplifying means for amplifying the electric signal, wherein the amplifying means realizes the matching of the input impedance with the signal source resistance by negative feedback, and furthermore, makes the voltage across the load equal to the reference voltage. Voltage control means for controlling the reference voltage and changing the reference voltage according to the ambient temperature so as to cancel the change in gain of the amplifying means, AC negative feedback means for applying AC negative feedback, and DC negative feedback for applying DC negative feedback. Means, and the AC negative feedback means and the DC negative feedback means have a temperature coefficient which cancels a change in the gain of the amplifying means which changes according to the ambient temperature.

[0021]

In the first infrared light detecting device of the present invention, the first amplifying section of the amplifying means has its input terminals connected in parallel and
Multiple feedback amplification circuits with resistors connected to each output terminal
And the output of these feedback amplifier circuits
And configured to take out and synthesize through the resistor.
The signal components of the outputs of the plurality of feedback amplifier circuits are
They are in phase with each other. For this reason, the plurality
Current due to mutual interference between each output of the feedback amplifier
While preventing the flow, the input impedance of the second
-Dance can be raised. Input of the second amplifying unit
If the force impedance is high, the feedback of each of the first
Through the resistor connected to the output terminal of the feedback amplifier
Since the current flowing into the second amplifying unit is small, the signal
For components, their resistance can be neglected.
Therefore, the first increase by the amount corresponding to the resistance value of those resistors.
By setting the resistance value of the feedback resistor of each feedback amplifier circuit in the width part low
Noise generated by each feedback amplifier circuit is reduced.
You.

Further, the second amplification section has an input impedance.
It is composed of a non-inverting amplifier with high dance
And each feedback amplifier circuit of the first amplifying unit has its own
There is no need to drive the resistor connected to the output terminal. There
Then, the resistance value of the resistor of the first amplifying unit is set to be low.
Even if the noise generated from these resistors is suppressed, the first amplification
There is no problem of the drive capacity of the unit.

[0023] Therefore, it is possible to achieve even better low noise amplification than before.

In the second infrared light detecting device of the present invention, since the amplifying means realizes the matching of the input impedance with the signal source resistance by the negative feedback, it is possible to generate the signal as compared with the case where the impedance matching resistor is connected. There is little noise.

In addition, when the ambient temperature changes, the reference voltage of the voltage control means changes so as to cancel the change in the gain of the amplification means, and the AC negative feedback means and the DC negative feedback means change the current of the amplification means. Since it changes so as to cancel the change in gain, it is very stable against changes in ambient temperature.

[0026]

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

FIG. 1 is a schematic diagram showing one embodiment of the infrared light detecting device of the present invention, FIG. 2 is a circuit diagram thereof, and FIG. 3 is a perspective view of a head to which an infrared light detector is attached.

(Overall Configuration) Infrared light detecting device 1 of the present invention
Includes an infrared light detector D and an amplifier AMP that amplifies an electric signal generated by the infrared light detector D. A bias voltage is applied to the detector D by a bias power supply VB.

(Infrared Light Detector) The infrared light detector D is composed of a photoconductive type MCT crystal, and generates an electric signal according to the intensity of the infrared light when irradiated with infrared light. In this embodiment, as shown in FIG. 3, the detector D is attached to a metal head 5 provided inside a cryogenic container (Dewar bottle) 2. The infrared light is introduced from a window 4 provided in the infrared light introducing section 3 of the low-temperature container 2 and irradiates the detector D. The head 5 is adjacent to the chamber 2a and is cooled to 77K by liquid nitrogen contained in the chamber 2a. By cooling, thermal noise generated by the MCT crystal can be reduced. The detector D is cooled by liquid nitrogen via the head 5. The electric signal generated by the detector D is
It is taken out of the container 2 through D.

A direct current is supplied to the detector D through a bias resistor RB (see FIG. 2). When the detector D is irradiated with infrared light, the resistance of the detector D is proportional to the light intensity.
RD decreases slightly, and as a result, the potential at the connection point A between the detector D and the bias resistor RB changes. Then, if this potential change is taken out as a signal, the absolute value of the intensity of the irradiated infrared light can be measured.

(Bias Power Supply) The bias power supply VB is connected to the detector D via a lead wire LD and supplies a predetermined DC voltage to the detector D.

(Amplifier) FIG. 5 is a circuit diagram showing an example of a circuit configuration of the amplifier AMP. This amplifier AMP
Since it is connected to the infrared light detector D via the capacitor C1, the DC signal and the low frequency signal are not amplified. It is suitable for amplifying a high frequency signal (for example, 10 kHz to 100 MHz).

This amplifier AMP has a two-stage configuration using two transistors Q1 and Q2 having a common emitter.
Further, an error amplifier Q3 and an inverting amplifier Q4 for stabilizing a bias voltage supplied to the transistors Q1 and Q2.
It has.

Vcc is a bias power supply, VREF is a reference power supply for generating a reference voltage Vstd of the error amplifier Q3, RC is a collector resistance of the transistor Q1, and RE is an emitter resistance of the transistor Q2.

The input signal is supplied to the first signal via the capacitor C1.
It is input to the base of the transistor Q1 in the stage. The output signal is taken from the emitter of the second transistor Q2. The operation of the transistors Q1 and Q2 is the same as that of the conventional amplifier 61 shown in FIG.

In this amplifier AMP, a conventional amplifier 61
Different from DC and AC, negative feedback is applied.
That is, the negative feedback of AC is applied to the base of the transistor Q1 of the first stage from the emitter of the transistor Q2 of the second stage via the AC feedback resistor RFac and the capacitor C4. Further, the output of the error amplifier Q3 is connected to the inverting amplifier Q3.
4. DC feedback is applied to the base of the transistor Q1 in the first stage via the DC feedback resistor RFdc and the resistor R3. The DC feedback circuit includes a DC feedback resistor RFd
The ground is connected between the resistor c and the resistor R3 via the resistor R4 and the capacitor C5.

The minus terminal of the error amplifier Q3 is connected to the collector of the transistor Q1 via a resistor R2.
The terminal is connected to one end of the collector resistor RC of the transistor Q1 via the reference power supply VREF. Part of the output of the error amplifier Q3 is fed back to the negative terminal via the capacitor C3.

The error amplifier Q3 is a differential amplifier. When the voltage between both ends of the collector resistor RC fluctuates and an error occurs between the error and the reference voltage Vstd given by the reference power supply VREF, the error is amplified and the transistor is amplified. A correction signal is injected into the base of Q1. Thus, the error amplifier Q3 detects the voltage across the collector resistor RC of the transistor Q1, and operates so that the voltage is always equal to the reference voltage Vstd.
As a result, the current flowing through the collector resistor RC is constant, and if the base current to the transistor Q2 is negligible, the current flowing through the transistor Q1 is constant. At this time, if the bias power supply VCC is constant, the collector voltage of the transistor Q1 also becomes constant, and the gain of the first-stage amplifier becomes stable. The transistor Q2 is an emitter follower having a voltage gain of about 1 and the gain is basically stable.

The reference power supply VREF is configured such that the reference voltage Vstd changes according to the change in the ambient temperature, thereby canceling the change in the gain of the transistor Q1 caused by the change in the ambient temperature. The reference power supply VREF having such a function can be realized by using a resistor whose resistance value changes at a desired rate in proportion to the ambient temperature. Alternatively, it can be realized by using a known IC capable of extracting a voltage or a current proportional to the ambient temperature.

The inverting amplifier Q4 adjusts the polarity.
It is connected to the output of the error amplifier Q3.

Error amplifier Q3, inverting amplifier Q4, resistor R
2, R3, R4, DC feedback resistor RFdc, reference power supply VREF, and capacitors C3, C5 constitute voltage control means.

Since the amplification factor of the amplifier AMP is determined by the physical constant of the transistor, it is basically constant regardless of the variation and the type of the transistors Q1 and Q2. Therefore, the reproducibility is excellent, the temperature can be corrected well, and the gain stability of, for example, 100 to 200 ppm / ° C is not difficult. Further, since the bias voltage and the bias current are kept constant and negative feedback is applied, the amplifying action of the transistors Q1 and Q2 is also stabilized. Further, since the matching of the input impedance is equivalently realized by the negative feedback without using the matching resistor serving as a noise source, the noise is low.

Further, since the amplifier AMP divides the negative feedback circuit into an AC feedback circuit and a DC feedback circuit, the amount of AC feedback and the amount of DC feedback can be set independently of each other. As a result, the setting of the operating point is easy. Thus, the degree of freedom of design is increased.
For example, DC negative feedback can be set at the point of minimum noise in the first stage, and AC negative feedback can be set independently so that the input impedance matches.

Next, a description will be given of conditions under which the gains and input impedances of the transistors Q1 and Q2 are kept constant even when the ambient temperature changes.

Considering one transistor, the voltage gain Gv when the emitter is grounded is expressed as follows.

First, assuming that the feedback resistance of the transistor is Rc, the emitter current ie is represented by the equation: ie = VREF / Rc. The transconductance gm is gm = q · ie / kT, where q is the charge of electrons and k is Boltzmann. The constant, T, is the absolute temperature.

Therefore, the voltage gain Gv of the transistor
Gv = gm Rc = (q / kT) VREF (1)

From equation (1), it can be seen that the voltage gain Gv changes in inverse proportion to the temperature T. Therefore, the reference voltage V
If REF is changed in proportion to temperature T, voltage gain Gv does not change with temperature T.

That is, if the reference voltage VREF is changed so that (VREF / T) = α (constant), Gv = (q / k) · (VREF / T) = (q / k) · α (2) The voltage gain Gv can be kept constant even when the ambient temperature changes.

As will be described below, the input impedance Zi of the transistor also changes according to the change in the ambient temperature.

The input impedance Zi of the common emitter transistor Q is as follows: Zi = rb + (hfe / gm) = rb + (q · α · hfe / k · Rc) where rb is the base resistance of the transistor and hfe is the current. The amplification factor and Rc are feedback resistors.

In a high-frequency transistor, rb is usually several Ω.
Therefore, since it can be ignored, Zi ≒ (q · α / k · Rc) · hfe (3)

The current amplification factor hfe is usually +7000 ppm
Since it has a temperature coefficient of about / ° C, it is understood that the input impedance Zi changes depending on the ambient temperature.

Therefore, in this AC amplifier , if a temperature coefficient is given to the resistance value of the AC feedback resistor RFac so as to satisfy the relationship of the above equation (3), it is possible to compensate the temperature change of the input impedance of the AC amplifier. As a result, the input impedance and the voltage gain of the amplifier AMP can be kept constant over a wide temperature range.

For example, in an amplifier having a voltage gain of 40 dB and an input impedance of 50 Ω, simulation shows that if a temperature coefficient of −800 to −850 ppm / ° C. is given to the feedback resistor, the change in input impedance can be canceled by a change in temperature. , The input impedance can be constant over a wide temperature range.

The collector resistance RC is, for example, 750
Ω, the emitter resistance RE is, for example, 1 kΩ, and the AC feedback resistance RF
ac is, for example, 11.5 kΩ, DC feedback resistance RFdc is, for example, 20 kΩ, resistance R2 is, for example, 1 MΩ, and resistance R3 is, for example, 1 kΩ.
For example, kΩ, the resistance R4 is 1 kΩ, the capacitor C1 is 5 μF, the capacitor C3 is 0.33 μF, the capacitor C4 is 0.33 μF, and the capacitor C5 is 0.33 μF, for example.

The voltage amplifying means is not limited to the above-described configuration, but may have another configuration as long as it performs the same operation as described above. As the amplifying element, transistors Q1, Q2
Other known amplifying elements (for example, FET and HEMT) can be used.

Here, the AC amplifier has a circuit configuration of two-stage amplification, but may have one-stage amplification or three or more stages.

(Amplifier) FIG. 4 is a circuit diagram showing another example of the circuit configuration of the amplifier AMP. This amplifier AMP
Are directly connected to the detector D without using the coupling capacitor C1, so that the DC signal and the low-frequency signal (for example, D
C to 200 kHz) with low noise. Here, the amplifier AMP has a two-stage configuration including a first amplifier and a second amplifier.

The first amplifying unit 10 is configured by connecting four identical feedback amplifier circuits in parallel, and amplifies an input signal . Those feedback amplifier circuits are the conventional amplifier 51 shown in FIG.
Has the same configuration as each feedback amplifier circuit of the first amplifier section. That is, each feedback amplifier circuit has a common input, and all input signals are input to the operational amplifiers A1 to A4 from the + terminals thereof. The negative terminals of the operational amplifiers A1 to A4 are grounded via feedback resistors RS1 to RS4, respectively. Operational amplifier A1 ~
Some of the output of A4 is the operational amplifier A1~A4 respectively via the feedback resistor R F 1~R F 4 - is fed back to the terminal. The output sides of the operational amplifiers A1 to A4 are connected to resistors R1 to R4, respectively. The outputs are taken out via the resistors R1 to R4, combined, and sent to the second amplifier. here,
Each of the four feedback amplifier circuits has an input impedance
It is configured as a high non-inverting amplifier.

The operational amplifiers A1 to A4 are all of the same type, and the feedback resistors RF1 to RF4 have the same resistance value. Further, the feedback resistors RS1 to RS4 also have the same resistance value, and the output side resistors R1 to R4 also have the same resistance value.

The second amplifying section is composed of one feedback amplifier circuit having an operational amplifier Aa and a feedback resistor RFa. The output obtained by combining the outputs of the four feedback amplifier circuits of the first amplifier is input to the operational amplifier Aa from its + terminal. The negative terminal of the operational amplifier Aa is grounded via a feedback resistor RSa. Part of the output of the operational amplifier Aa is a feedback resistor RF
The signal is fed back to the negative terminal of the operational amplifier Aa via a. The output of the operational amplifier Aa is sent from an output terminal. here,
The feedback amplifier circuit is configured as the same non-inverting amplifier as the first amplifier.
Has been established.

The input impedance of the operational amplifier Aa of the second amplifying unit is at least equal to or greater than the parallel resistance of the resistors R1 to R4, that is, equal to or greater than the parallel resistance of the resistors R1 to R4.
It should be bigger . If the resistance is smaller than the parallel resistance , the first increase
The signal component of the composite output from the width part increases with the resistances R1 to R4.
The voltage is divided and attenuated by the input impedance of the band Aa.
This is because the S / N ratio decreases, and a sufficient noise reduction effect cannot be obtained.

The input impedance of the second amplifier is preferably at least 10 times, more preferably at least 100 times, the parallel resistance of the resistors R1 to R4.

In the amplifier AMP of the present invention, the first amplifier
Since the output signal components of each feedback amplifier circuit are in phase,
Signal inflow and outflow between the outputs of each feedback amplifier
No mutual interference occurs, and the input impedance of the second amplifying unit is set to be equal to or larger than the parallel resistance value of the resistors R1 to R4 of the first amplifying unit. The current flowing into the second amplifier is small. Therefore, the resistors R1 to R4 can be ignored for the signal component, and each amplifier circuit of the first amplifier does not need to drive the resistors R1 to R4.

Therefore, according to the resistance values of the resistors R1 to R4,
Since the resistance values of the feedback resistors RS1 to RS4 and RF1 to RF4 of the first amplifier can be set low, the combined resistance of the feedback resistors RS1 to RS4 and RF1 to RF4 decreases, and The generated noise is reduced as compared with the conventional case.

In this amplifier AMP, the noise of each feedback amplifier circuit of the first amplifier section reduced as described above is further reduced.
By connecting four feedback amplifiers in parallel (1/1 /
4) Since ^1/2 = 1/2, the noise of the entire first amplification unit is greatly reduced. As a result, even better low-noise amplification than before becomes possible.

The gain of the first amplifier is the same as the gain of each amplifier circuit of the first amplifier.

In this embodiment, the four feedback amplifier circuits of the first amplifier section have exactly the same configuration. However, if the feedback amplifier circuits have the same gain, even if some of the components are different. Alternatively, the same constituent elements may have different numerical values and the like. Further, other types of amplifier circuits that do not use the operational amplifiers A1 to A4 may be used as long as they are feedback amplifier circuits.

(Confirmation Test) In order to confirm the effect of this amplifier AMP, this amplifier AMP and a conventional amplifier 51 were manufactured and tested under the following test conditions. Amplifier AMP
Has the circuit configuration shown in FIG. 4, and the conventional amplifier 51 has the circuit configuration shown in FIG. 7 and the number of feedback amplifier circuits of the first amplifier is four.

(Test conditions) Amplifier AMP of the present invention First amplifier Operational amplifiers A1 to A4: LT1028 Feedback resistors RF1 to RF4: 760Ω Feedback resistors RS1 to RS4: 10Ω Resistors R1 to R4: 1 kΩ Gain: 77 times Second amplification Unit Operational amplifier Aa: AD829 Feedback resistance RFa: 300Ω Feedback resistance RSa: 1 kΩ Gain: 1.3 times Gain of entire amplifier: 100 times Conventional amplifier 51 First amplifier Operation amplifiers A1 to A4: LT1028 Feedback resistors RF1 to RF4: 1.2 kΩ Feedback resistors RS1 to RS4: 50Ω Synthetic resistors R1 to R4: 2 kΩ Gain: 25 times 2nd amplifier Operational amplifier Aa: AD829 Feedback resistor RFa: 2 kΩ Gain: 4 times Gain of entire amplifier: 100 times (test result) The results obtained are: Preamplifier PA of the invention: noise level 0.47n
V / (Hz) ^1/2 conventional amplifier 51: noise level 0.64n
V / (Hz) ^1/2 , and it was confirmed that this amplifier AMP had significantly lower noise than the conventional amplifier 51.

In this embodiment, the number of feedback amplifier circuits in the first amplifier is four, but it may be set to any number other than four. Further, the second amplifying unit may be a buffer instead of the amplifying circuit. Furthermore, the combined output of the first amplifying unit may be directly input to the load without providing the second amplifying unit, or another circuit such as an amplifying circuit may be provided before the first amplifying unit.

Further, the first amplifier is appropriately provided by a suitable number of feedback amplifier circuits.
The amplification unit may be configured as a unit, a plurality of these units may be connected, and the number of units to be used may be changed by a switch as needed. This has the advantage that the first amplifier having a desired noise level can be easily obtained while keeping the gain constant.

In the above embodiment, a photoconductive MCT crystal is used as the infrared light detector D, but a photovoltaic MCT crystal is used.
A crystal may be used, and other known infrared light detectors can be used as long as they detect infrared light and generate an electric signal.

As the bias power source VB, a bias power source other than the above-described circuit configuration can be used as long as it has low noise.

[0076]

As described above, the first infrared light detecting device of the present invention has a simple structure and extremely low noise.

The operation of the second infrared light detecting device of the present invention is extremely stable with respect to a change in ambient temperature.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an infrared light detection device of the present invention.

FIG. 2 is a circuit diagram of the infrared light detection device of FIG.

FIG. 3 is a perspective view of a head to which an infrared light detector is attached.

FIG. 4 is a circuit diagram illustrating an example of a circuit configuration of an amplifier.

FIG. 5 is a circuit diagram showing another example of the circuit configuration of the amplifier.

FIG. 6 is a conceptual diagram of a feedback amplifier.

FIG. 7 is a circuit diagram showing an example of a conventional amplifier.

FIG. 8 is a circuit diagram showing another example of the conventional amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Infrared light detection device 2 Low temperature container 2a room 3 Container light introduction part 4 Window of light introduction part 5 Detector mounting head D Infrared light detector LD Lead wire RB Bias resistance RD Infrared light detector resistance VB Bias power supply AMP amplifier A1 to A4 Operational amplifier RS1 to RS4, RF1 to RF4 Feedback resistance R1 to R4 Resistance Aa Operational amplifier RFa Feedback resistance RSa Feedback resistance Q1, Q2 Transistor Q3 Error amplifier Q4 Inverting amplifier RC Collector resistance RE Emitter resistance RFac AC feedback Resistance RFdc DC feedback resistance R2, R3, R4 Resistance C1, C3, C4, C5 Capacitor VREF Reference power supply VCC Power supply voltage

Continuation of front page (72) Inventor Chihiro Kato 5-1-5 Minamimagome, Ota-ku, Tokyo (72) Inventor Hiroo Hamaguchi 5-10-7-407, Koyodai, Inagi-shi, Tokyo (56) References JP-A-63-63 172930 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01J 1/44

Claims (2)

(57) [Claims] An infrared light detecting means for receiving an infrared light and generating an electric signal corresponding to the infrared light, and an amplifying means coupled to the detecting means and amplifying the electric signal generated by the detecting means. Wherein each of the input terminals is connected in parallel;
Multiple feedback amplifiers with resistors connected to each output terminal
And the outputs of those feedback amplifier circuits correspond to
A first amplifying unit for taking out and synthesizing through the resistor,
Of the first amplification circuit obtained by combining the outputs of the feedback amplification circuits.
The output of the width section is input and has the configuration of a non-inverting amplifier circuit
And a second amplifying unit, and the first amplifying unit
The output signal components of the plurality of feedback amplifier circuits are in phase with each other.
And the input impedance of the second amplifier
Is each of the plurality of feedback amplification circuits of the first amplification unit.
The infrared light detection device, which is equal to or more than a parallel resistance value of the resistor connected to an output terminal . 2. An infrared light detecting means for receiving an infrared light and generating an electric signal according to the infrared light, and an amplifying means coupled to the detecting means and amplifying the electric signal generated by the detecting means. The amplifying means realizes the matching of the input impedance with the signal source resistance by negative feedback, and controls the voltage between both ends of the load to be equal to the reference voltage, and the reference voltage becomes equal to the ambient temperature. A voltage control means for changing so as to cancel a change in gain of the amplification means, an AC negative feedback means for applying an AC negative feedback, and a DC negative feedback means for applying a DC negative feedback. An infrared light detecting device, wherein the feedback means and the DC negative feedback means have a temperature coefficient that cancels a change in gain of the amplifying means that changes in accordance with an ambient temperature.