JP4920487B2 - Reference voltage generator - Google Patents

Description

  The present invention relates to a reference voltage device, and more particularly to a reference voltage generation device (substrate module) suitable for application to a semiconductor inspection device and a DC-type voltage / current application measuring instrument built in a measurement power source.

  To economically realize a reference voltage generator that generates a plurality of reference voltages having relatively high stability in a reference voltage generation circuit of a DC system voltage / current application measuring instrument built in a semiconductor inspection device, a measurement power source, etc. Is desired. First, the accuracy, accuracy, and relative accuracy of some terms used in this specification will be outlined.

  Accuracy is used for accuracy relative to national and international standards.

  The accuracy is used for the degree of follow-up of the inspection apparatus with respect to the calibration device or the accuracy relative to the value of the calibration device.

  Relative accuracy is used for the accuracy of the ratio of values within the same DC module and the degree of coincidence of the same value between two or more DC modules. The former (accuracy of the ratio of values in the same DC module) is also called “linearity”. The relative accuracy may be used to mean the degree of coincidence (reproducibility) when, for example, the same value is generated and measured at time intervals, but in this specification, reproducibility refers to accuracy and accuracy. include.

  A measurement power source (DC module for measurement) mounted on an inspection apparatus or the like is configured to perform voltage measurement or voltage measurement by performing voltage application or current application. DC module.

  Hereinafter, the problem of the conventional measurement power supply will be described. The problems described below are based solely on the results of studies by the present inventors.

  A measurement power source (DC module for measurement) has a built-in reference voltage circuit to guarantee an output value (applied voltage / current value) and a measured value. The reference voltage does not directly guarantee the accuracy and accuracy of the system, but is a secondary reference. For example, a digital multimeter or an equivalent measuring instrument (hereinafter referred to as “DMM”) specialized in calibration, One inspection device is installed, and the measured value of the reference voltage is calibrated at any time to guarantee indirectly. Calibration is performed by the DMM when the system is turned on, at rest, or when a significant temperature change occurs.

  In a measurement power source such as a desktop type (bench top), it is extremely expensive to adopt a configuration in which a calibration DMM is incorporated in order to ensure accuracy and accuracy.

  In other words, the configuration in which the calibration DMM is incorporated in the measurement power supply is not suitable for small-scale applications of several power supplies even when the number of pins and the number of power supplies are increased (not profitable). For this reason, the accuracy and accuracy must be compromised.

  Even if there are a plurality of reference voltages, they are used for calibration or reference for each measurement range, and the accuracy and resolution of ADC (analog / digital conversion circuit) and DAC (digital / analog conversion circuit) cannot be improved. For example, in the case of 16-bit resolution in the 1 V range, the 16-bit resolution does not change even in the 10 V range.

  In general, the accuracy and accuracy of a measurement system are often defined as four times the standard deviation (occurrence probability 0.006%) in terms of distribution width. In consideration of irreversible fluctuation (hysteresis) due to operation and storage environment in addition to long-term fluctuation, it is necessary to set the daily variation to about a fraction of the guaranteed value.

  If you want to improve the level of products on the market by an order of magnitude (for example, accuracy of 1 mV or less in the 10 V range, relative accuracy of 100 uV) industrially and economically, the existing technology (state of the arts) Need to overcome the essential barriers. This is the knowledge of the present inventors who have a long track record in this field.

  The problem of stably generating absolute values and relative values of a plurality of reference voltages having different values will be verified below to clarify the problems.

The semiconductor device which is the main element has a current I, a voltage V and an absolute temperature T in its operation theory (PN junction).
I∝exp (qV / kT)
A relationship exists. Here, q is a unit charge of electrons, and k is a Boltzmann constant. When using a thermal temperature VT = kT / q (VT is 26 mV at 300K), I∝exp (V / VT)
As is well known, the temperature dependence (temperature coefficient) of the positive voltage of the silicon diode is approximately −2 mV / ° C. at room temperature. The movement of electrons, holes, etc. is governed by similar factors.

  In silicon crystals, carrier mobility has crystal axis dependence and is also a function of stress. Not only the diode characteristics but also the resistance value is affected by stress due to the piezoresistance effect. The stress is applied to the semiconductor element due to the sealing structure and the mounting of the printed wiring board. Due to the difference in thermal characteristics, the stress also has temperature dependence, and complicated temperature characteristics can be obtained without applying mechanical force from the outside. It is easy to guess.

  In many cases, the reference voltage circuit, such as a well-known Zener diode or band gap voltage reference circuit, has a combination of conflicting characteristics such as adding positive and negative temperature coefficient voltages. In other words, the circuit technology is devised to obtain a stable temperature characteristic of the voltage.

  However, there is a limit to this, and a voltage reference element that can be economically achieved as an industrial product has a temperature dependency of several ppm / ° C.

  Assuming that the temperature dependence of the voltage reference element is ± 5 ppm / ° C. at 10 v, an error of 10 v ± 0.5 mv occurs in the reference voltage when used in an environment of ± 10 ° C.

  In industrial use, in a 16-bit ADC / DAC frequently used for power supply devices and the like, the absolute value is equivalent to the voltage reference element described above, so the accuracy is equivalent, and the resolution (LSB) is ± 10 V. Since 0.305 mV, the linearity is 2 to 4 LSB (Least Significant Bit), it is ± 0.5 to 1 mv.

  The voltage dividing resistor also has a temperature characteristic of several ppm / ° C.

  Although there is a method of improvement using an integrated network resistance, there is a problem of cost.

  In the operational amplifier (Op-Amp), fluctuations due to the temperature characteristics of the input offset voltage and the common mode (in-phase) voltage occur from several tens uV to several hundreds uV, and fluctuate depending on the temperature. In particular, the change in the common mode is complicated, and there are cases where it cannot be corrected by the linear expression. Although there is a chopper type operational amplifier, there is a problem of switch noise, and its application is limited.

  One measure is to use an oven as a countermeasure against temperature drift, but large objects that keep the entire equipment and the entire board at a constant temperature (constant temperature) are not suitable for the application.

  In addition, when a method of incorporating a heater in the voltage reference element is used, there is no effect on temperature fluctuations of the peripheral elements, and therefore the purpose cannot be achieved by this alone.

  Accordingly, an object of the present invention is to provide a reference voltage circuit capable of generating a reference voltage that can maintain accuracy without permanently installing a calibration DMM.

  Another object of the present invention is to provide a reference voltage circuit capable of supplying a plurality of reference voltages having a relative accuracy more stable than that of a DAC or ADC when mounted on a system using a DAC or ADC. is there.

  Still another object of the present invention is to provide a stable and highly accurate reference voltage circuit that suppresses an increase in cost.

  In order to solve the above problems, the invention disclosed in the present application is generally configured as follows.

A reference voltage generation device (module) according to one aspect (side surface) of the present invention includes a first voltage reference element and a second voltage reference element for calibrating the first voltage reference element. A reference voltage generator;
A voltage dividing resistor that divides the output voltage of the first voltage reference element by resistance and outputs a plurality of voltages having different values;
A plurality of buffer amplifiers each receiving and outputting a plurality of voltages of the voltage dividing resistor;
First and second temperature detection elements respectively disposed in association with the first and second voltage reference elements;
First and second heating elements respectively disposed in association with the first and second voltage reference elements;
First and second temperature control circuits for controlling the first and second heating elements based on the respective temperature detection results of the first and second temperature detection elements;
A voltage comparator that compares the voltages of the first and second voltage reference elements and outputs a voltage supplied to an output voltage adjustment trim terminal of the first voltage reference element;
Comprising a substrate including
A heat insulating cover covering the first and second voltage reference elements, the voltage dividing resistor, the buffer amplifier, the first and second temperature detection elements, and the first and second heating elements; Prepared,
The second voltage reference element, the second temperature detection element corresponding to the second voltage reference element, and the second heating element are in a region covered with the heat insulating cover of the substrate. Arranged at one end,
The first voltage reference element, the first temperature detection element corresponding to the first voltage reference element, and the first heating element are within a region covered with the heat insulating cover of the substrate. And disposed on the side opposite to the one side end. A circuit element disposed on the substrate and between the first temperature detection element and the second temperature detection element is controlled to operate at a constant temperature corresponding to a position where the circuit element is disposed. .

  In the present invention, the second voltage reference element includes a Zener diode, and the Zener diode is disposed on one side end portion in the region covered with the heat insulating cover on the substrate, and the second temperature reference element. The detection element, the second temperature control circuit, and the second heating element are controlled so that the ambient temperature of the Zener diode is maintained at a temperature at which the temperature characteristic of the Zener diode becomes flat. Also good.

In the present invention, in the region covered with the heat insulating cover, the reference voltage generation unit having the first and second voltage reference elements, the voltage dividing resistor, the plurality of buffer amplifiers, and the first The first and second temperature detecting elements are disposed on the main surface of the substrate;
The first and second heating elements may be arranged at positions corresponding to the first and second voltage reference elements on the surface opposite to the main surface of the substrate.

  In the present invention, the first and second temperature control circuits respectively supply currents to flow through the first and second heating elements according to the detection results of the first and second temperature detection elements, respectively. First and second transistors that are variable are provided.

  In the present invention, one end of the second voltage reference element is supplied with a reference voltage via an output of a buffer that receives the output of the first voltage reference element, and the other end of the second voltage reference element is Are connected in common to a ground potential to which the first voltage reference element is connected.

  In the present invention, the reference voltage generator includes a first resistor and a second resistor connected in series between an output of the buffer that receives an output of the first voltage reference element and a ground potential, and the second resistor An output adjustment circuit that can adjust the resistance value of the first resistor, and a trim terminal of the first voltage reference element is connected to a midpoint of the second resistor and is externally provided on the substrate. It is good also as a structure connected also to a trim terminal.

  In the present invention, an output voltage from the voltage comparator or a trim voltage supplied from the outside may be supplied to the external trim terminal.

In the present invention, an output terminal of the first temperature detection element is connected to an output of a buffer that receives a reference voltage output from the first voltage reference element via a resistor,
An output terminal of the second temperature detection element is connected to an output of the buffer that receives a reference voltage output from the first voltage reference element via a resistor, and the first temperature control circuit includes the first temperature control circuit. A first differential amplifier circuit that varies a bias voltage of the first transistor based on an output voltage of the temperature detection element and an output voltage of the buffer that receives an output of the first voltage reference element; The second temperature control circuit determines a bias voltage of the second transistor based on an output voltage of the second temperature detection element and an output voltage of the buffer that receives an output of the first voltage reference element. It is good also as a structure provided with the 2nd differential amplifier circuit made variable.

An apparatus according to another aspect of the present invention includes a reference voltage generation unit including a first voltage reference element;
A voltage dividing resistor that divides the output voltage of the first voltage reference element by resistance and outputs a plurality of voltages having different values;
A plurality of buffer amplifiers each receiving and outputting a plurality of voltages of the voltage dividing resistor;
A first temperature sensing element disposed in the vicinity of the first voltage reference element;
A first heating element disposed in the vicinity of the first voltage reference element;
A temperature control circuit for receiving the detection result of the first temperature detection element and controlling the first heating element;
On the substrate,
A heat insulating cover is provided to cover one end of the substrate, the first voltage reference element, the voltage dividing resistor, the buffer amplifier, and the first heating element.

  In the present invention, the first voltage reference element has a trim terminal for adjusting an output voltage of the first voltage reference element, receives a trim voltage from the outside, and supplies the trim voltage to the trim terminal of the voltage reference element. An adjustment circuit is provided.

  In the present invention, a reference voltage generation unit including the first voltage reference element, the voltage dividing resistor, the plurality of buffer amplifiers, and the first temperature detection in a region covered with the heat insulating cover. An element is disposed on the main surface of the substrate, and the first heating element is disposed at a position corresponding to the first voltage reference element on a surface opposite to the main surface of the substrate.

  In this invention, the 2nd temperature detection element is provided in the area | region which is not covered with the said heat insulation cover on the said board | substrate.

  In the present invention, an inverting amplifier for inputting an output voltage of one tap of the voltage dividing resistor and outputting an inverted signal is provided. The voltage dividing resistor includes a plurality of resistors connected in series between the output of the first voltage reference element and the one tap, and a series of a feedback path between the output of the inverting amplifier and the one tap. A plurality of resistors connected to each other. In the present invention, a circuit may be provided that adjusts the input offset of the inverting amplifier and adjusts the output voltage of the inverting amplifier. In the present invention, the inverting amplifier is preferably arranged in a region covered with the heat insulating cover.

  In the present invention, a plurality of reference voltages from the reference voltage generation circuit may be supplied to a plurality of systems via a bus line to which the substrate is connected.

An apparatus according to another aspect of the present invention is a reference voltage generation apparatus used in a voltage / current application measuring apparatus that constitutes a measurement power source, and includes a first voltage reference element and calibration of the first voltage reference element. A reference voltage generator having a second voltage reference element for performing,
A buffer amplifier that receives the output of the first voltage reference element, generates a plurality of reference voltages having different values by a voltage dividing resistor, and distributes the reference voltage;
A first temperature detection element disposed in the vicinity of the first voltage reference element; and a second temperature detection element on the printed board.
A first heating element for heating the printed board;
Based on the detection result of the first temperature detection element or the detection results of the first temperature detection element and the second temperature detection element, the first heating element or the first heat generation. The reference voltage generating unit has a constant temperature due to the body and the second heating element, and the circuit element disposed between the first temperature detection element and the second temperature detection element is the circuit element. Means for controlling the temperature so as to be a constant temperature corresponding to the position where
With
The reference voltage generator, the voltage dividing resistor, and the buffer amplifier are covered with a heat insulating cover,
The second voltage reference element of the reference voltage generation unit is disposed at the end of the printed board, facilitating temperature control and making it difficult for mechanical stress to be transmitted.

  In the present invention, the heat insulating cover covers a part of the printed board and enables temperature control within an operation guarantee range.

  In the present invention, the first temperature detection unit is disposed in the vicinity of the boundary between the substrate part of the printed board covered with the heat insulating cover and the substrate part not covered, and is covered with the heat insulating cover. A second temperature control circuit is provided for making the temperature gradient of the substrate portion on which the voltage reference element, the voltage dividing resistor, and the buffer amplifier are mounted constant.

  In the present invention, when the reference voltage generating unit is a positive or negative unipolar output, and a bipolar output is obtained, an inverting amplifier using a dividing resistor as an input resistor and a feedback resistor is provided to obtain an inverted output. It is good also as a structure.

  In the present invention, in order to cancel the input offset voltage of the inverting amplifier, the offset voltage is detected by an operational amplifier having a small input offset voltage, and feedback is applied directly or indirectly, and the 0v point of the voltage dividing resistor is set to the ground potential. The circuit may be provided with a circuit for adjusting the output voltage of the inverting amplifier.

  A circuit board according to another aspect of the present invention is a heat insulating cover that covers a region including at least one side end portion of the substrate, and a side opposite to the one side end portion in the region covered with the heat insulating cover of the substrate. A first temperature detection element and a first heating element, and a second temperature detection disposed at the one end in the region covered with the heat insulating cover of the substrate. First and second temperature controls that receive the temperature detection results of the element and the second heating element and the first and second temperature detection elements, respectively, and control the first and second heating elements, respectively. A predetermined circuit element (for example, a temperature) disposed between the first temperature detection element and the second temperature detection element on the substrate in a region covered with the heat insulating cover. Sensitive circuit element) at a constant temperature corresponding to the position where the circuit element is placed Unishi to have. A reference voltage generation device according to the present invention includes the circuit board, and the first heating element and the second heating element are disposed in a region of the surface opposite to the main surface of the substrate and covered with the heat insulating cover. A heating element, and at least one voltage reference element corresponding to at least one of the first and second heating elements on the main surface of the substrate, the first, first, A voltage dividing resistor, a plurality of buffer amplifiers each receiving and outputting a plurality of voltages of the voltage dividing resistor, and an inverting amplifier, the output voltage of the voltage reference element being the voltage The inverting amplifier generates another reference voltage to be supplied to the other end of the voltage dividing resistor, and generates a plurality of different potentials from a plurality of taps of the voltage dividing resistor. A reference voltage is taken.

  In the present invention, the first voltage reference element has a trim terminal for adjusting an output voltage of the first voltage reference element, and compares the voltages of the first and second voltage reference elements to compare the first voltage reference element and the first voltage reference element. A voltage comparator for controlling the voltage of the trim terminal for adjusting the output voltage of one voltage reference element is provided.

  According to the present invention, it is possible to generate a reference voltage that can maintain accuracy without permanently installing a calibration DMM.

  In addition, when the reference voltage circuit of the present invention is mounted on a system equipped with a commercially available DAC (digital-analog converter) or ADC (analog-digital converter), a plurality of stable relative accuracy than a commercially available DAC or ADC is provided. A reference voltage can be supplied.

  According to the present invention, it is possible to supply a highly stable and highly accurate reference voltage while suppressing an increase in cost.

  The above-described present invention will be described below with reference to the accompanying drawings in order to explain in more detail. In the following description, the voltage reference element for self-calibration / control is the second voltage reference element (1.2), and the generation element of the reference voltage Vref (G) supplied to the output unit is the first voltage reference element (1.2). The voltage reference element (1.1) is assumed. In the reference voltage generation circuit of the present invention, when mounted on a system using a DAC or ADC, at least a plurality of reference voltages having a relative accuracy higher than that of the DAC or ADC are supplied, and a plurality of reference voltage outputs are directly output. It can be used as a highly stable front DAC.

  In the ADC, the relative accuracy can be improved by switching a plurality of reference voltages according to the input and converting only the difference by the comparison method.

  Although not particularly limited, in the reference voltage generation circuit of the present invention, since the reference voltage is distributed to a plurality of systems, the plurality of reference voltages are, for example, linear step outputs. This eliminates the dynamic instability factor found in the switching method by the combination of switches, and the bus line type power supply mode is obtained in which all the reference voltages can be obtained stably at all times. In the present invention, the plurality of reference voltages are not limited to linear steps. If there is a practical request, in addition to the linear steps, voltages necessary for calibration and voltages frequently used in applied systems are used. Of course, it is also possible to supply the above.

  In the reference voltage generation circuit according to the present invention, the reference voltage is generated by voltage division resistors (Rs1 to Rsm +, Rsm− to Rsn) of the same type and the same value at equal intervals. The buffer amplifiers (BA1 to BAm +, BAm− to BAn) that receive the divided voltage by the resistance division and output the voltage are basically required by the number of reference voltages. Since the temperature characteristics such as the offset voltage of the buffer amplifier are individual, the buffer amplifier also needs to be temperature controlled.

  The reference voltage generation circuit according to the present invention is a design method that does not use a special component material for the semiconductor component and the dividing resistor, and can be handled by a commercially available product, thereby suppressing an increase in cost and being economical.

  In the reference voltage generation circuit of the present invention, the temperature control is performed to improve the temperature characteristics of the reference voltage generation unit, the voltage dividing resistor, the buffer amplifier, etc. The system is easy to assemble (assembly, manufacturing process, maintenance), and the operation cost is reduced.

  The specific configuration of the reference voltage generation circuit of the present invention is as follows. That is, a reference voltage source used in a voltage / current application measuring device that constitutes a measurement power source such as a semiconductor inspection device, and the voltage reference element has a plurality of resistance networks (equally spaced resistance division) (2.1). A buffer amplifier (2.2) for generating a reference voltage and distributing the reference voltage (s) is provided. These circuit elements are arranged on a printed circuit board (PCB) (10) so that the temperature gradient is appropriate, and the temperature detection element Rts1 (3.2) is arranged in the vicinity of the voltage reference element (1.2). The temperature detection element Rts2 (8.2) is provided in a part suitable for detecting a temperature gradient due to the ambient temperature. Then, another temperature control unit (referred to as “auxiliary temperature control unit”) (8) and a heating element (referred to as “auxiliary heating element”) (8.1) for controlling the temperature in the vicinity of the temperature detection element (8.2). ).

The temperature can be controlled in a multifaceted manner. If necessary, the temperature controller (3) and the auxiliary temperature controller (8)
-Keep the temperature detection element 3.2 side of the PCB (10) at a relatively high temperature,
The temperature detection element 8.2 part is kept relatively low and above room temperature, and
A PCB partitioned by the temperature detection elements (3.2) and (8.2) by controlling the detection temperatures at the temperature detection elements (3.2) and (8.2) to be constant temperatures. The region (10) is set to have a substantially constant temperature gradient. The circuit elements (circuit elements on which temperature control is performed) mounted on the PCB (10) partitioned by the temperature detection elements (3.2) and (8.2) are constant according to the arrangement positions of the circuit elements. Controlled to be at temperature.

  Furthermore, in the present invention, in order to prevent short-term temperature changes, the reference voltage generator (1), the voltage dividing resistor (2.1), the buffer amplifier (2.2), etc. ) Cover with (7).

  A temperature sensitive component such as a voltage reference element, a resistor network, a buffer amplifier, and an inverting amplifier is placed in a heat insulating cover (7), and between the temperature detection element (3.2) and the temperature detection element (8.2). Deploy. In order to perform temperature control efficiently and easily, the voltage reference element (1.2) is arranged at the end of the PCB (10) to facilitate temperature control and to prevent mechanical stress from being transmitted. And

  In order to avoid an excessive temperature rise due to self-heating, the heat insulating cover (7) does not cover the entire PCB (10), and the structure is such that heat can be appropriately released and temperature control can be performed within the guaranteed operating range. To do. For example, the voltage reference element (1.1), voltage dividing resistor (2.1), buffer amplifier (voltage buffer) (2.2) on the surface of the PCB (10), temperature control transistor (3.4), PCB (10) The heating element (3.1) and the auxiliary heating element (8.1) on the back surface are covered with a heat insulating cover (7). The voltage reference element (1.1) is disposed between the temperature detection element (3.2) and the temperature detection element (8.2).

  Since the influence of the ambient temperature cannot be completely eliminated, a temperature detection element (Rts2) (8.2) is provided at the boundary of the heat insulating material of the PCB (10), and the temperature is controlled by the temperature control circuit (8). The temperature of two places near the heating element (3.1) at the end of the printed board 10 and the vicinity of the auxiliary heating element (8.1) is monitored, and the part covered with the heat insulating cover (7) (heating element) The temperature gradient of the substrate between (3.1) and the auxiliary heating element (8.1) is made substantially constant so as not to be affected by the ambient temperature. The output reference voltage is stabilized by temperature monitoring and control results at these two locations.

  In the present invention, in the case where the reference voltage source is a positive electrode or a negative electrode and a bipolar output is obtained, an inverting amplifier (A4) using a dividing resistor as an input resistor and a feedback resistor is provided in order to obtain an inverted output. .

  In order to cancel the input offset voltage of the inverting amplifier (A4), the operational amplifier (A5) having a small input offset voltage detects the offset voltage and applies feedback directly or indirectly, and the inverting input terminal (−), ie, The 0v point of the voltage dividing resistor (2.1) is set to the ground potential. With this circuit configuration, a chopper type amplifier can be employed for A5, and temperature and time fluctuations at the 0v point can be reduced.

  Further, in order to match the gain of the inverting amplifier (A4), the inverting amplifier (5) is provided with a gain fine adjustment terminal Vref (n) _adj. The offset canceling effect makes it possible to adjust the voltage on the negative electrode side while keeping the voltage ratio stable. Hereinafter, it explains in full detail according to an Example.

  FIG. 1 is a diagram illustrating a configuration example of a circuit for generating a reference voltage Vref (G) according to an embodiment of the present invention. Vref (G) generation unit 1, Ref-V generation unit 2, temperature control circuit 3, auxiliary temperature control circuit 8, Vref (G) adjustment circuit 4, inverting amplifier (Amp) 5, and two references A voltage comparator 9 for comparing voltages and a power supply circuit 6 are provided.

  The Vref (G) generator 1 includes a voltage reference element 1.1 connected between a power supply and an analog GND. The voltage reference element 1.1 includes a trim terminal, the output voltage is adjusted, and the reference voltage Ref (G) is output from the refv terminal. Although not particularly limited, a high-precision reference (ultra-low drift, ultra-low noise, long-term stability, high-precision output voltage) such as LT1236A (manufactured by Linear Technology) is used as the voltage reference element 1.1.

  In this embodiment, the Vref (G) generator 1 includes a voltage reference element 1.2 for internally calibrating and controlling the reference voltage Ref (G).

  The voltage reference element 1.2 must have a higher voltage reproducibility than the voltage reference element 1.1. However, the voltage reference element 1.2 can obtain a predetermined voltage reproducibility in a relatively narrow temperature range. The noise characteristics may not be as strict as the voltage reference element 1.1.

  A zener diode DZ is used as an example of the voltage reference element 1.2. In the voltage reference element 1.2, the Zener diode DZ has an anode connected to the analog ground A-Gnd and a cathode connected to the output terminal of the buffer BA0 via the resistor RZ. The input terminal of the buffer BA0 is connected to the refv terminal of the voltage reference element 1.1. The connection point between the Zener diode DZ and the resistor RZ is connected to the input terminal at the position of the voltage comparator 9 via the buffer amplifier Az. An output adjustment circuit (Vref-adj) 4 in which a resistor R4 and a variable resistor VR2 are connected in series is provided between the output terminal of the buffer BA0 and the analog ground, and a resistor R5 is provided at a midpoint between both ends of the variable resistor VR2. To the trim terminal of the voltage reference element 1.1.

  The Ref-V generation unit 2 includes voltage dividing resistors 2.1 (resistance arrays Rs1, Rs2,... Rsm +, Rsm−, Rsn−1, Rsn). Vref (G) is divided by a plurality of resistor arrays Rs1 to Rsn which are a plurality of reference voltages. Buffer Amp2.2 (BA1, BA2, BAm +, BAm-, BAn-1, BAn) is connected to the tap of the resistor array, and buffer Amp2.2 (BA1, BA2, BAm +, BAm-, BAn-1, BAn). Respectively output reference voltages Vref (1), Vref (2), Vref (m +), Vref (m−), Vref (n−1), and Vref (n). The buffer Amp (BA0) is used for voltage supply of the internal circuit.

  The voltage comparator 9 compares the reference voltage Vref (G) generated by the voltage reference element 1.1 with the output voltage of the voltage reference element 1.2 (the output voltage of the amplifier AZ receiving the Zener voltage at the input), Feedback is applied directly (or via a computer or the like) to the trim terminal of the voltage reference element 1.1. The output voltage of the voltage reference element 1.1 having the trim terminal may be adjusted by supplying an external voltage from the Vtrim terminal after the voltage reference element 1.1 is attached to the PCB (10 in FIG. 2). . In the connector 11, the output terminal Vdiffout and the Vtrim terminal of the voltage comparator 9 may be connected to each other, or connection / non-connection may be controlled via a switch (not shown) or the like.

  The operational amplifier A4 of the inverting Amp5 generates a negative electrode (for example, −10v) from the positive electrode (for example, + 10v) of Vref (G).

  The inverting input terminal (−) of the operational amplifier A4 is connected to the midpoint tap (0v point) of the voltage dividing resistor 2.1. The voltage dividing resistor 2.1 includes resistors Rs1, Rs2,... Rsm + connected in series between the output (Ref (G)) of the voltage reference element 1.1 and the midpoint tap, and the operational amplifier A4. A plurality of resistors Rsm−,... Rsn−1, Rsn connected in series in a feedback path between the output terminal and the inverting input terminal (= the midpoint tap). The resistors Rs1, Rs2,... Rsm + connected in series constitute the input resistor Rs of the operational amplifier A4, and the resistors Rsm−,... Rsn−1, Rsn connected in series are the feedback resistors Rf of the operational amplifier A4. The operational amplifier A4 functions as an inverting amplifier with amplification factor = −Rf / Rs.

  The inverting input terminal (−) of the operational amplifier A5 of the inverting Amp5 is connected to the middle point of the resistors Rsm + and Rsm− via the resistor R10, and the non-inverting input terminal (+) is connected to the ground potential A-GND. A5 detects the offset Vos. When the Offset_det terminal and the Vos adjustment terminal are connected to each other, the output of the operational amplifier A5 is divided by the resistors R9 and R8 and input to the non-inverting input terminal (+) of the inverting Amp4. Feedback is applied so that the inverting input terminal (−) has the same potential as A-Gnd, and Vos≈ (input offset of A5), which becomes smaller according to the input offset of the operational amplifier A5. In this adjustment, the dotted line between the Offset_det and the Vos adjustment terminal may be cut, and detection and offset adjustment may be performed indirectly. Capacitors C1 and R10 form a filter in a high frequency region, and suppress switch noise when a chopper Amp or the like is used for the operational amplifier A5.

  Another advantage of the offset canceller is that voltage adjustment on the negative polarity side can be performed independently of the positive polarity side by applying a voltage from the Vref (n) _adj terminal. The accuracy of the measurement power supply device that applies and measures voltage as an industrial product can be improved economically. For example, 1 mv accuracy can be achieved at 10 v output, and a stable ratio, that is, linearity can be secured between a plurality of reference voltages therebetween.

  As a result, the magnitude relationship of the voltage, which is one of the most basic characteristics of the analog circuit, can be determined with high accuracy and high resolution. For example, non-linearity inspection of ADC and DAC can be applied to products with higher bits (high resolution).

  The divided voltage of the voltage dividing resistor 2.1 is output as the reference voltages Vref (1), Vref (2),..., Vref (n) via the buffer amplifier 2.2. These absolute values and temperature characteristics are measured by an external calibration DMM (not shown) and recorded in a memory device (not shown) that is always readable.

  A bus line is configured and a reference voltage is supplied to a plurality of DC modules.

  The temperature control circuit 3 includes a temperature detection element (Rts1) 3.2, and an output terminal of the temperature detection element 3.2 is an output of the buffer amplifier BA0 that receives the output pressure Ref (G) from the voltage reference element 1.1. It is connected to the end via a resistor R2. The temperature control circuit 3 differentially inputs the output voltage of the temperature detection element 3.2 and the voltage obtained by dividing the output voltage of the buffer BA0 by the resistor R1 and the variable resistor VR1, and the bipolar transistor Q1 (temperature control of FIG. 2). A differential amplifier A1 that varies the base voltage of TRS3.4) is provided. The differential amplifier A1 controls the emitter current of the bipolar transistor Q1, and controls the amount of heat generated by the heating element 3.1. Each temperature detection element 3.2 receives a terminal voltage of a resistor (temperature sensing resistor or platinum temperature measuring resistor) Rts1 and outputs a corresponding voltage.

  The temperature control circuit 8 that controls the amount of heat generated by the second heating element 8 according to the detection result of the temperature detection element 8.2 has the same configuration as the temperature control circuit 3. The output terminal of the temperature detection element 8.2 is connected to the output terminal of the buffer amplifier BA0 that receives the reference voltage output from the voltage reference element 1.1 via the resistor R3. Similar to the temperature control circuit 3, the temperature control circuit 8 generates a voltage obtained by dividing the output voltage of the temperature detection element 8.2 and the output voltage of the buffer BA 0 by a resistor (not shown) and a variable resistor (not shown). There is provided a differential amplifier (corresponding to A1 of the temperature control circuit 3 in FIG. 1) that differentially inputs and varies the base voltage of the bipolar transistor Q2 (temperature control TRS 8.4 in FIG. 2). This differential amplifier (not shown) controls the emitter current of the bipolar transistor Q2, and controls the amount of heat generated by the auxiliary heating element 8.1. The temperature detection element 8.2 receives a terminal voltage of a resistor (temperature sensing resistor or platinum temperature measuring resistor) Rts2 and outputs a corresponding voltage.

  The power supply circuit 6 receives GND, positive / negative power supply + Vspu / −Vspu, and supplies power supply to each part.

  The first voltage reference element, the first temperature detection element, the first temperature control circuit, and the first heating element according to claim 1 are the same as the voltage reference element 1.1 of FIG. It corresponds to the element (Rts2) 8.2, the temperature control circuit 8 (differential amplifier and transistor Q2, etc.), the auxiliary heating element 8.1, respectively, the second voltage reference element, the second temperature detection element, the second The temperature control circuit and the second heating element are the voltage reference element 1.2, the temperature detection element (Rts1) 3.2, the temperature control circuit 3 (differential amplifier A1 and transistor Q1, etc.), the heating element 3. 1 corresponds to each.

  FIG. 2 is a diagram showing a PCB board on which the reference voltage circuit of this embodiment is mounted. 2A is a top view and FIG. 2B is a side view. Each circuit element of FIG. 1 is arranged as shown in FIG. 2, and a reference voltage (Vref (G)) generation unit 1, a division resistor 2.1, and a buffer amplifier 2.2 are covered with a heat insulating cover 7. A heating element 3.1 is provided at one end of the back surface of the substrate covered with the heat insulating cover 7, and an auxiliary heating element 8.1 is provided at the other end of the back surface of the substrate covered with the heat insulating cover 7. Yes. A voltage reference element 1.2, a temperature detection element (Rts1) 3.2, and a temperature control transistor 3.4 (Q1 in FIG. 1) are provided on a substrate surface (a heating element arrangement portion) at a position corresponding to the heating element 3.1. The voltage reference element 1.1, the temperature detection element (Rts2) 8.2, and the temperature control transistor 3.4 (Q2 in FIG. 1) are provided on the substrate surface at a position corresponding to the auxiliary heating element 8.1. Is provided.

  The output voltage of the voltage reference element 1.1 having the trim terminal is adjusted by the variable resistance element VR2 of the Vref (G) adjustment circuit 4 after the voltage reference element 1.1 is mounted on the PCB 10.

  The temperature detecting element 8.2 is disposed at the boundary of the heat insulating cover 7 and detects the boundary temperature of the heat insulating cover 7.

  Although not particularly limited, in this embodiment, the nominal value of the reference voltage Ref (G) of the voltage reference element 1.1 is set to an output voltage of 10 v and the temperature characteristic is ± 5 ppm / ° C. This is expanded to −10v by the voltage dividing resistor 2.1 and the inversion Amp5, and the interval is linearly divided in 2v steps. Dividing from 2v and -2v, 1v and -1v were also added, and used for calibration of the internal amplifier to expand the application range.

  In this example, for the resistance, the absolute value of the temperature coefficient was small, uniform, and the lead type was used to avoid stress by selecting a manufacturing method, value, and grade so as not to cause an extreme cost increase. .

  Each of 10 outputs, 1v, and -1v divided by -10v to 10v by resistors, and the reference Gnd potential is buffered by the buffer amplifier 2.2, and external outputs Vref (1) to Vref (M +), A-Gnd, Vref (m−) to Vref (n). The buffer amplifier 2.2 is low in noise, and the input current is selected so that the IR drop of the dividing resistor does not adversely affect and the absolute value of the input offset voltage and the temperature drift are small.

  The operational amplifier A4 of the inverting Amp5 is exactly the same, but since the influence of the offset is large, the operational amplifier A5 of FIG. Then, feedback was applied so that the contact potential was always 0v. Although not particularly limited, in the present embodiment, since the noise countermeasure is given the first priority, the operational amplifier has a level at which the offset is likely to be a problem. However, the noise problem can be solved. The voltage ratio between the plus side and the minus side can be changed by connecting an arbitrary connection point (tap) of the dividing resistor 2.1 to the feedback terminal (−input terminal) of the operational amplifier A4.

  In the temperature control circuit 3, the temperature detecting element 3.2 (temperature sensing resistor or platinum temperature measuring resistor) Rts1 is arranged in the immediate vicinity of the voltage reference element 1.2 to control the heating element (resistance) 3.1. .

  Similarly, the temperature control circuit 8 controls the heating element 8.1.

  The relative accuracy was examined using only the voltage reference element 1.1. The set temperature was adjusted by the variable resistance element VR1 to 45 to 50 ° C., and the operation was performed at an ambient temperature of 15 to 35 ° C. In this state, the voltage is set to 10 v by the variable resistance element VR2 of the Vref (G) adjustment circuit 4.

  The boundary temperature of the heat insulation cover 7 is detected by the resistor Rts2 of the temperature detection element 8.2 at the boundary of the heat insulation cover 7, and the boundary temperature is directly controlled by the temperature control circuit 8 and output from the terminal Vtb2 to the outside. It is possible to respond to temperature changes immediately after turning on. That is, immediately after the start after the switch is turned on, since the temperature is in a transient state from the outside air temperature, measures and measures such as avoiding calibration by the voltage reference element 1.2 until the target temperature is reached and stabilized can be implemented.

  Next, the effect of the present embodiment will be described.

  FIG. 3 is a diagram showing temperature characteristics according to the above embodiment, and is a case where there is no temperature control. The horizontal axis represents the output reference voltage Vref, and the vertical axis represents the error from the nominal value of the Vref output (= the numerical value on the X axis). Ambient temperature 15 ° C. (diamond) and 25 ° C. (triangle) are shown as parameters.

  On the other hand, FIG. 4 shows a case where temperature control is performed on the same board in this embodiment.

  In FIG. 3, from the difference between two broken lines corresponding to temperatures of 15 ° C. and 25 ° C., 200 uv / 10 v / 10 ° C. = 2 ppm / ° C., which is within the specification range of the voltage reference element 1.1.

  In FIG. 4, when viewed on the same scale, two broken lines corresponding to temperatures of 15 ° C. and 25 ° C. are overlapped and an improvement of one digit or more is performed.

  When the approximate heater power consumed is set to 60 ° C. on the temperature control side and 45 ° C. on the auxiliary temperature control side, the heat generating part 3.1 is 0.6 w, the heat generating part 8.1 is 1.0 w at an ambient temperature of 15 ° C., 25 It became 0.6 w at 35 ° C. and 0 w at 35 ° C.

  Since the power consumption excluding the heating elements (heaters) 3.1 and 8.1 in FIG. 1 is about 0.6 w, it is sufficiently small and efficient as a voltage source that can simultaneously output 10 or more reference voltages in parallel. is there.

  Next, a method for adjusting a reference voltage output in a circuit manner by detecting a temperature change regardless of temperature control will be discussed.

In a two-way orthogonal experiment with temperatures 8 and 23 ° C., with / without temperature control, the terminal Vtrim in FIG.
Vref 10v = 10.00002v
The relative accuracy was compared.

  When there was no temperature control When the temperature was 8 ° C., the output voltage Vref (= 10 v) was adjusted by changing the Vtrim of the adjustment circuit 4 entirely.

  FIG. 5 shows an example of the result. Vref (8 ° C.) is subtracted from Vref (23 ° C.) using the presence or absence of temperature control as a parameter, and each reference voltage is plotted on the horizontal axis. Although the temperature change can be adjusted by Vtrim (diamonds), the variation (deviation) is large.

Standard deviation is
Temperature control (square heater): 6 uv / 10 ° C
Whereas
Vtrim (rhombus Vtrim): 16 uv / 10 ° C
It became.

  Since Vref = 10v is set, a difference of (division resistance + buffer amplifier) changes.

  Thus, when only the voltage reference element 1.1 was adjusted, the relative ratio between the respective reference voltages was insufficient, and the superiority of the temperature control could be confirmed.

  By ensuring the relative accuracy and monitoring and correcting the voltage reference element with a measuring instrument having an absolute value traceability, the accuracy of each reference voltage can be improved.

  A description will be given of a method of producing a practical effect in accordance with external monitoring by replacing the above-described measuring instrument with the voltage reference element 1.2.

  The reference voltage Vref (G) generated by the voltage reference element 1.1 and the output of the voltage reference element 1.2 are compared by the voltage comparator 9, and the voltage reference element 1.1 is directly connected to a trim terminal or a computer. And so on. This mitigates step-wise voltage changes (a kind of hysteresis phenomenon caused by stress) caused by exposure to temperature changes during storage and transportation, day and night temperature changes, air conditioning ON-OFF, etc., and accuracy To prevent deterioration.

  Needless to say, one of the voltage reference elements 1.1 and 1.2 is sufficient if the accuracy can be relaxed.

  Hereinafter, the reason why the two reference voltages are employed in this embodiment will be described. The second reference voltage (voltage reference element 1.2) for internal calibration is required to generate a stable and reproducible voltage.

  The stability level of the integrated reference voltage IC is roughly the same as the technical level of the internal reference voltage of a commercially available ADC or DAC, and when trying to obtain higher accuracy and accuracy as in the present invention. Various problems become apparent. For example, even when the operating temperature is constant, the history of stress remains due to the history of the storage temperature from the material of the printed circuit board, the mounting structure, etc., and then the voltage does not recover to the original value even if the temperature is constant, A hysteresis phenomenon occurs. The fluctuating voltage may become so large that it is affected even at the storage temperature to be guaranteed as the measurement power source. As an example, FIG. 6 shows the drift of the voltage reference element due to the standing (storage) temperature.

  FIG. 6 shows that the integrated reference element change (ΔVref) and Zener diode voltage change (ΔVz) are mounted on the same printed circuit board, and the temperature is controlled to ± 0.5 ° C. during operation. This is data that is turned on for 8 hours and turned off for 16 hours including nighttime, and changes the leaving conditions during the off time (experimental data by the present inventors).

  ΔVref shows a step variation of 0.16 mV when stored at −20 ° C. Although not shown, according to the repetition of the experiment, the ΔVref fluctuation is affected by the temperature history, but cannot be quantitatively reproduced, and control of 0.1 mV or less must be determined to be difficult.

  Although ΔVz in FIG. 6 compared was mounted on the same PCB, no significant variation was observed, and a single product was subjected to a plurality of temperature cycles, but no significant variation was observed. However, since diodes are also sensitive to mechanical stress, as a hypothesis, if a temperature history is not a stress history, a 2-pin diode is easier than a multi-pin IC structure. It is a proof of that it is.

  FIG. 7 shows an example of a measurement result of temperature characteristics of a general-purpose commercial product Zener diode. In FIG. 7, the temperature change of the voltage output is dotted (see ■) and approximated by a quadratic equation (see solid line).

  In FIG. 7, there is a maximum point around 61 ° C., that is, a portion having a temperature coefficient of approximately ± 0.

  For general-purpose Zener diodes, detailed temperature characteristics are outside the range of the product specifications, so when a commercially available product was measured at room temperature and 50 ° C, the temperature characteristic variation of one voltage category (± 50mv) is 70uv / ° C with standard deviation. Met. The temperature that shows the maximum point is also widely distributed, and some practical selection and individual correspondence must be taken into consideration for practical use.

  Zener diodes have the advantage of a temperature coefficient of ± 0 at a specific temperature and the ability to relieve stress due to temperature history, but on the other hand, the zener voltage varies greatly and is highly stable, such as a voltage fine adjustment circuit, for use as a reference power supply. There is a need for a supplementary circuit with the characteristics.

  On the other hand, the reference voltage IC used as the voltage reference element 1.1 has the above-described characteristics necessary for practical use, and allows fine adjustment of the output voltage.

  Therefore, in this embodiment, a combination that takes advantage of both advantages can be an industrial solution. Vref (G) is generated by the reference voltage IC (voltage reference element 1.1 in FIG. 1), a Zener diode is used as the voltage reference element 1.2, and after reaching a temperature having a temperature coefficient ± 0, the voltage reference The element 1.2 is used for calibration to control Vref (G). That is, the output Vdiffout of the voltage comparator 9 is turned back from the connector 11 and input to the trim terminal and supplied to the trim terminal of the voltage reference element 1.1.

  As shown in FIGS. 1 and 2, in the embodiment having two reference voltage sources, the set temperature of the voltage reference element 1.1 is relatively low, which contributes to shortening the stabilization time after the switch is turned on.

  FIG. 8 is a diagram showing the configuration of the second exemplary embodiment of the present invention. In the present embodiment, unlike the embodiment shown in FIG. 1, the reference voltage generating unit 1 is configured by the voltage reference element 1.1 and the voltage reference element 1.2 is omitted. Further, instead of the voltage comparator 9 of FIG. 1, a reference voltage adjusting unit 4 is provided that applies a trim voltage to the trim terminal of the voltage reference element 1.1. The reference voltage adjusting unit 4 has resistors R6 and R6 ′ connected between the trim terminal and the ground, and one end connected to a connection point between the resistors R6 and R6 ′, and a middle point connected to the voltage reference element 1.1 via the resistor R5. The other end of the variable resistor VR2 is connected to the output Vref (G) of the reference voltage generator 1 via the resistor R4. The temperature detector 3.3 may be disposed in the vicinity of the region covered with the heat insulating cover 7 and the region not covered with the heat insulating cover 7.

  Although the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the configurations of the above-described embodiments, and various modifications that can be made by those skilled in the art within the scope of the present invention. Of course, including modifications.

It is a figure which shows the structure of the reference voltage generation circuit of one Example of this invention. (A), (B) is the top view and side view of the board of one Example of this invention. It is a figure (without temperature control) which shows the temperature characteristic of the reference voltage in one Example of this invention. It is a figure (with temperature control) which shows the temperature characteristic of the reference voltage in one Example of this invention. It is a figure which shows the relative error of temperature control of the reference voltage and Vtrim adjustment in one Example of this invention. It is an example of the dependence of the voltage drift on the standing temperature, and is a diagram comparing an integrated voltage reference element (ΔVref) and a Zener diode (ΔVz). It is a figure which shows the temperature characteristic of the reference voltage for internal calibration in one Example of this invention. It is a figure which shows the structure of the reference voltage generation circuit of another Example of this invention. (A), (B) is the top view and side view of the board of another Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reference voltage (Vref (G)) generation part 1.1 Voltage reference element 1.2 Voltage reference element 2 Ref-V production | generation part 2.1 Voltage dividing resistance 2.2 Buffer amplifier 3 Temperature control circuit 3.1 Heating element 3 .2 Temperature detection element 3.3 Temperature detection element 3.4 Temperature control transistor (TRS)
4 Vref (G) adjustment circuit 5 Inverting amplifier 6 Power supply circuit 7 Thermal insulation cover 8 Second temperature control unit (auxiliary temperature control unit)
8.1 Second heating element 8.2 Second temperature detection element 8.4 Temperature control transistor (TRS)
9 Voltage comparator 10 Printed board 11 Connector

Claims (26)

A reference voltage generator having a first voltage reference element and a second voltage reference element for calibrating the first voltage reference element;
A voltage dividing resistor that divides the output voltage of the first voltage reference element by resistance and outputs a plurality of voltages having different values;
A plurality of buffer amplifiers each receiving and outputting a plurality of voltages of the voltage dividing resistor;
First and second temperature detection elements respectively disposed in association with the first and second voltage reference elements;
First and second heating elements respectively disposed in association with the first and second voltage reference elements;
First and second temperature control circuits for controlling the first and second heating elements based on the respective temperature detection results of the first and second temperature detection elements;
A voltage comparator that compares the voltages of the first and second voltage reference elements and outputs a voltage supplied to an output voltage adjustment trim terminal of the first voltage reference element;
Comprising a substrate including
A heat insulating cover covering the first and second voltage reference elements, the voltage dividing resistor, the buffer amplifier, the first and second temperature detection elements, and the first and second heating elements; Prepared,
The second voltage reference element, the second temperature detection element corresponding to the second voltage reference element, and the second heating element are in a region covered with the heat insulating cover of the substrate. Arranged at one end,
The first voltage reference element, the first temperature detection element corresponding to the first voltage reference element, and the first heating element are within a region covered with the heat insulating cover of the substrate. The reference voltage generating device is arranged on a side opposite to the one end portion. The second voltage reference element includes a Zener diode;
The Zener diode is disposed on one side end portion in the region covered with the heat insulating cover on the substrate,
The ambient temperature of the Zener diode is controlled by the second temperature detection element, the second temperature control circuit, and the second heating element so as to be maintained at a temperature at which the temperature characteristic of the Zener diode becomes flat. The reference voltage generation device according to claim 1, wherein In the region covered with the heat insulating cover, the reference voltage generation unit having the first and second voltage reference elements, the voltage dividing resistor, the plurality of buffer amplifiers, and the first and second And a temperature detection element is disposed on the main surface of the substrate,
The said 1st and 2nd heat generating body is arrange | positioned in the position respectively corresponding to a said 1st and 2nd voltage reference element in the surface on the opposite side to the main surface of the said board | substrate. The reference voltage generation device according to 1.   The first and second temperature control circuits vary the currents flowing through the first and second heating elements according to the detection results of the first and second temperature detection elements, respectively. The reference voltage generation device according to claim 1, further comprising: a first transistor and a second transistor. In the reference voltage generator, a reference voltage is supplied to one end of the second voltage reference element via an output of a buffer that receives an output of the first voltage reference element.
The reference voltage generation device according to claim 1, wherein the other end of the second voltage reference element is connected in common to a ground potential to which the first voltage reference element is connected. The reference voltage generator includes a first resistor and a second resistor connected in series between an output of the buffer that receives an output of the first voltage reference element and a ground potential, and a resistance of the second resistor The value has an output adjustment circuit that can be adjusted,
6. The trim terminal of the first voltage reference element is connected to a midpoint of the second resistor and is also connected to an external trim terminal provided on the substrate. The reference voltage generator described.   The reference voltage generation device according to claim 6, wherein an output voltage from the voltage comparator or a trim voltage supplied from the outside is supplied to the external trim terminal. An output terminal of the first temperature detection element is connected to an output of a buffer that receives a reference voltage output from the first voltage reference element via a resistor,
An output terminal of the second temperature detection element is connected to an output of the buffer that receives a reference voltage output from the first voltage reference element via a resistor,
The first temperature control circuit determines a bias voltage of the first transistor based on an output voltage of the first temperature detection element and an output voltage of the buffer that receives an output of the first voltage reference element. A first differential amplifier circuit that is variable;
The second temperature control circuit determines a bias voltage of the second transistor based on an output voltage of the second temperature detection element and an output voltage of the buffer that receives an output of the first voltage reference element. The reference voltage generation device according to claim 4, further comprising a second differential amplifier circuit that is variable. A reference voltage generator including a first voltage reference element;
A voltage dividing resistor that divides the output voltage of the first voltage reference element by resistance and outputs a plurality of voltages having different values;
A plurality of buffer amplifiers each receiving and outputting a plurality of voltages of the voltage dividing resistor;
First temperature detecting elements respectively disposed in association with the first voltage reference elements;
First heating elements respectively disposed in association with the first voltage reference elements;
A first temperature control circuit that receives the detection result of the first temperature detection element and controls the first heating element;
On the substrate,
A heat insulating cover is provided to cover one side end of the substrate, the first voltage reference element, the voltage dividing resistor, the buffer amplifier, and the first heating element. A reference voltage generator.   The reference voltage generation device according to claim 9, further comprising a second temperature detection element in or outside the region covered with the heat insulating cover on the substrate. The first voltage reference element has a trim terminal for adjusting an output voltage of the first voltage reference element;
The reference voltage generation device according to claim 9, further comprising an adjustment circuit that receives a trimming voltage from the outside and supplies the trimming voltage to a trim terminal of the voltage reference element. In the region covered with the heat insulating cover, a reference voltage generation unit including the first voltage reference element, the voltage dividing resistor, the plurality of buffer amplifiers, and the first temperature detection element are: Disposed on the main surface of the substrate;
The reference voltage generation according to claim 9, wherein the first heating element is disposed at a position corresponding to the first voltage reference element on a surface opposite to the main surface of the substrate. apparatus. An inverting amplifier that inputs an output voltage of one tap of the voltage dividing resistor and outputs an inverted signal,
The voltage dividing resistor is:
A plurality of resistors connected in series between the output of the first voltage reference element and the one tap;
A plurality of resistors connected in series with a feedback path between the output of the inverting amplifier and the one tap;
The reference voltage generation device according to claim 1, wherein the reference voltage generation device is provided.   14. The reference voltage generation device according to claim 13, further comprising a circuit that adjusts an input offset of the inverting amplifier and adjusts an output voltage of the inverting amplifier.   14. The reference voltage generation device according to claim 13, wherein the inverting amplifier is disposed in a region covered with the heat insulating cover.   The reference voltage generation device according to claim 1, wherein the plurality of reference voltages from the reference voltage generation circuit are supplied to a plurality of systems via a bus line to which the substrate is connected. A reference voltage generation circuit used in a voltage / current application measuring device constituting a measurement power source,
A reference voltage generator having a first voltage reference element and a second voltage reference element for calibrating the first voltage reference element;
A buffer amplifier that receives the output of the first voltage reference element, generates a plurality of reference voltages having different values by a voltage dividing resistor, and distributes the reference voltage;
A first temperature detection element disposed in the vicinity of the first voltage reference element; and a second temperature detection element on the printed board.
A first heating element for heating the printed board;
Based on the detection result of the first temperature detection element or the detection results of the first temperature detection element and the second temperature detection element, the first heating element or the first heat generation. The reference voltage generating unit has a constant temperature due to the body and the second heating element, and the circuit element disposed between the first temperature detection element and the second temperature detection element is the circuit element. Means for controlling the temperature so as to be a constant temperature corresponding to the position where
With
The reference voltage generator, the voltage dividing resistor, and the buffer amplifier are covered with a heat insulating cover,
The second voltage reference element of the reference voltage generation unit is disposed at an end of the printed board, facilitates temperature control, and makes it difficult for mechanical stress to be transmitted. Reference voltage generator.   The reference voltage generation device according to claim 17, wherein the heat insulating cover covers a part of the printed board and enables temperature control within an operation guarantee range.   The first temperature detection unit is arranged in the vicinity of a boundary between a substrate portion covered with the heat insulating cover and an uncovered substrate portion of the printed board, and the voltage reference is covered with the heat insulating cover. 18. The reference voltage generation according to claim 17, further comprising a second temperature control circuit for making a temperature gradient of a substrate portion on which the element, the voltage dividing resistor, and the buffer amplifier are mounted constant. apparatus.   When the reference voltage generator is a positive or negative unipolar output and obtains a bipolar output, the reference voltage generator includes an inverting amplifier using a dividing resistor as an input resistor and a feedback resistor to obtain an inverted output. The reference voltage generation device according to claim 17, wherein   In order to cancel the input offset voltage of the inverting amplifier, the offset voltage is detected by an operational amplifier having a small input offset voltage, and feedback is applied directly or indirectly, the 0v point of the voltage dividing resistor is set to the ground potential, and the inversion is performed. 21. The reference voltage generation device according to claim 20, further comprising a circuit for adjusting an output voltage of the amplifier. A heat insulating covering covering a region including at least one side edge of the substrate;
A first temperature detection element and a first heating element disposed on the opposite side of the one end in the region covered with the heat insulating cover of the substrate;
A second temperature detecting element and a second heating element disposed at the one end in the region covered with the heat insulating cover of the substrate;
First and second temperature control circuits that receive temperature detection results from the first and second temperature detection elements, respectively, and control the first and second heating elements;
With
In the region covered with the heat insulating cover, a predetermined circuit element disposed between the first temperature detecting element and the second temperature detecting element is disposed on the substrate. A circuit board characterized by operating at a constant temperature corresponding to a position. A circuit board according to claim 22,
The first heating element and the second heating element are provided in a region of the surface opposite to the main surface of the substrate and covered with the heat insulating cover,
At least one voltage reference element corresponding to at least one of the first and second heating elements on the main surface of the substrate;
On the main surface of the substrate, between the first and second heating elements, a voltage dividing resistor, a plurality of buffer amplifiers each receiving and outputting a plurality of voltages of the voltage dividing resistor, and an inverting amplifier are provided. ,
The output voltage of the voltage reference element is supplied as one reference voltage to one end of the voltage dividing resistor,
The inverting amplifier generates another reference voltage to be supplied to the other end of the voltage dividing resistor;
A reference voltage generating device, wherein a plurality of reference voltages having different potentials are taken out from a plurality of taps of the voltage dividing resistor. A first voltage reference element and a second voltage reference element corresponding to the first and second heating elements, respectively, on the main surface of the substrate;
The output voltage of the first voltage reference element is supplied as one reference voltage to one end of the voltage dividing resistor,
The first voltage reference element has a trim terminal for adjusting an output voltage of the first voltage reference element;
The voltage comparator which controls the voltage of the trim terminal for the output voltage adjustment of the said 1st voltage reference element by comparing the voltage of the said 1st and 2nd voltage reference element, It is characterized by the above-mentioned. Item 23. The reference voltage generation device according to Item 22.   A module comprising the reference voltage generation device according to any one of claims 1 to 21, 23, and 24.   An inspection apparatus comprising the reference voltage generation device according to any one of claims 1 to 21, 23, and 24.

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