JPH0135364B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to solid state voltage references, and more particularly to an apparatus for temperature compensating a voltage reference and a simple method for setting the voltage reference to its best compensated state. be.

Solid state voltage references have junction voltage sources, such as Zener diodes, which have large temperature coefficients that require compensation.

For many reference devices, the voltage versus temperature relationship is:

V _dev = V _K + α (T-T _K ) (1) V _dev is the device terminal voltage at an arbitrary temperature T, V _K and T _K are constants, and α is a coefficient that changes depending on the device manufacturing process.

For example, a band gap junction source that has a temperature coefficient of opposite sign (slope) to the original and is appropriately scaled to a given output voltage level to compensate for changes in voltage due to temperature changes. The outputs of the devices can be summed with a compensation voltage circuit such as: The characteristics of such a compensated voltage reference device can be expressed by the following relational expression 2.

V _ref = λ [(V _G0 − βT) σ + V _K + α (T − T _K )] …(2) V _G0 is the band gap voltage, β is the temperature coefficient of the forward bias junction, and σ is the voltage reference The proportionality factor between the compensators, λ, is the overall scaling factor required to achieve a given voltage value.

Such a device has two degrees of freedom for adjustment, represented by σ (slope) and λ (scaling) in equation (2). The method of adjusting the device to achieve the specified operating characteristics is to use a computer algorithm to set σ to an appropriate value, minimize the change due to temperature to the calculated value α, and then adjust λ to achieve the specified output. This is a method to obtain the voltage V _ref '. This method therefore requires two separate adjustment steps, one for each of the two degrees of freedom of the control circuit.
However, experience has shown that this method is complex, expensive, undesirable, and, while commercially useful, is still not sufficient to achieve the desired performance. Therefore, there is a great need to improve this.

The solid state voltage reference device of the present invention follows a voltage versus temperature characteristic curve having a first slope.
a first voltage source means for generating a voltage of said first voltage and a second voltage according to a voltage versus temperature characteristic curve having a second slope, said second voltage being combined with said first voltage; and second voltage source means for generating a composite reference output voltage responsive to the second voltage. As shown in the embodiments described below, the first voltage source means is a voltage source 10, for example a Zener diode, and the second voltage source means is a bandgap voltage source represented by the base-emitter voltage of the transistor _Q1 or _Q2 . A voltage source means 24 includes a voltage source.

Control circuit means are provided which operate in conjunction with said second voltage source means. The control circuit means has two independent curve forms including as one of the forms the slope of the voltage versus temperature characteristic curve of the second voltage source means according to predetermined parameters of the elements of the control circuit means. and adjustable means for varying said second voltage and correspondingly varying said composite reference voltage.

In the embodiment shown in FIG. 1, the elements of the control circuit means are resistors 26, 28, and 30 constituting a voltage divider circuit connected to the base of the transistor _Q1 or _Q2 , and the voltage divider constants δ and ε are the parameters. It's summery. The adjustable means is an output voltage adjusting resistor R ₁ (or R ₂ ) connected to the emitter of the transistor Q ₁ (or Q ₂ ).
It is.

These transistors Q ₁ , Q ₂ , voltage dividing resistor 26,
28, 30, by mutually connecting the adjusting resistors R ₁ and R ₂ , when the composite voltage is preselected from a wide selectable range and adjusted to a particularly specified value, the voltage is adjusted in relation to the predetermined parameter. , in order to give a predetermined temperature coefficient to the composite voltage,
means for varying the second slope under control of the adjustable means as the second voltage is varied.

The predetermined parameters δ, ε give the slope and the position in the voltage axis direction of the voltage versus temperature characteristic curve of the second voltage source. In a particularly preferred embodiment shown in FIG.
The position and slope of (common intersection) are set in advance,
the slope substantially cancels the slope of the characteristic curve of the first voltage source, and its position is approximately at the same temperature T _K as the pivot point of the set of scattered characteristic curves Z of this first voltage source; Further, the voltage level is set such that a target composite reference voltage is obtained when the first and second voltages are applied. Note that the temperature and voltage at the pivot point (common intersection) are determined by extrapolation of each curve, and are at negative temperatures, which cannot physically occur.

The control circuit thus presets the form of the voltage versus temperature characteristic curve of the second voltage source, thereby
and the second voltage source.

Therefore, even if the slopes of the characteristic curves of the first and second voltage sources vary due to the manufacturing process, if the second voltage is varied by the adjustable means to obtain a prespecified composite reference voltage, Accordingly, the second slope is changed to automatically reproduce the predetermined temperature compensation at the target output voltage.

Another feature of the invention is revealed by the method of temperature compensation of the reference voltage. That is, the method includes connecting a first voltage of a solid-state voltage source to a second voltage source means for generating a second voltage, and applying the first voltage to the sum of said first and second voltages. Applied to the technique of temperature compensation by generating a corresponding composite reference voltage, the voltage versus temperature characteristic curves of said two voltages have opposite signs so that temperature effects tend to be canceled in said reference voltage. The method provides temperature compensation for the composite reference voltage of a specified value from a wide selectable range, the method comprising the following steps:

That is, control for controlling each of two independent curve forms including the slope of the characteristic curve of the second voltage source means as one of the forms, by controlling the elements of the control circuit means according to predetermined parameters. connecting circuit means to said second voltage source means; adjusting circuit elements of said control circuit means to vary said second voltage to bring said reference voltage to said specified value; The slope of the voltage versus temperature characteristic curve of the second voltage is controlled by adjustment of circuit elements, and the effect on the reference voltage due to the temperature characteristic of the first and second voltages, as well as other curve forms of the characteristic curve, is controlled. The purpose of the present invention is to generate a predetermined relationship between the reference voltages and give a predetermined temperature coefficient to the reference voltage when the reference voltage is adjusted to the specified value.

In conclusion, important aspects of the present invention provide two methods for controlling the output voltage-temperature characteristics of a voltage reference device by adjusting a single circuit element of the voltage reference device.
It has been found that extremely excellent results can be obtained by adopting a technique that simultaneously changes the two variable coefficients {λ and σ in equation (2)}. That is, in a preferred embodiment of the present invention, when the variable resistor is adjusted to make the reference output voltage a specified value, the temperature compensation control circuit simultaneously provides the best temperature compensation at the point where the reference voltage output is equal to the specified value. It is.

It has also been found that it is possible to reduce the two degrees of freedom used to perfectly adjust the voltage reference device to one degree of freedom, thereby improving the performance of the voltage reference device and at the same time simplifying the method of manufacture. 1 degree of freedom of adjustment
This can be understood mathematically if we consider that the variable λ depends on σ due to the topology of the associated control circuit for the compensation voltage source. This dependency relationship can be expressed by the following equation (3).

λ=V _ref ′/V _K +σV _G0 −αT _K …(3) V _ref ′ is the predetermined output voltage Therefore, the output voltage can be expressed by equation (4) V _ref =V _ref ′/V _K +σV _G0 −αT _K [(V _G0 -βT)σ +V _K +α(T−T _K )] …(4) If we rearrange equation (4), V _ref =V _ref ′σV _G0 +V _K −αT _K +(α −βσ)T/V _K +
σV _G0 −αT _K …(5) σ is the remaining adjustable parameter According to another important aspect of embodiments of the present invention, V _ref
By adjusting the term (α
−βσ) can be made zero, that is, βσ = α,
The desired zero temperature compensation is obtained, but within the limits of the device.

The present invention will now be described with reference to the accompanying drawings.
In FIG. 1, a voltage reference device according to the principles of the invention has a Zener diode voltage source 10 as a first voltage source, one electrode of which is connected to the output line 12 of an operational amplifier 14. .
This diode is connected via a negative feedback circuit to the inverting input terminal 16 of the amplifier, which terminal is connected via a resistor 18 to a common line or ground 20.

This Zener diode 10 is formed as part of an IC chip together with the associated control circuitry of FIG. The chip includes circuitry (not shown) for generating a regulated reference voltage as described below. Zener diode is
For example, US Patent Application No. 801410 (Patent No. 4136349)
Preferably, it is formed as an embedded device as disclosed in .

The potential of the non-inverting input terminal 22 of the amplifier 14 is fixed by a control circuit 24 having second voltage source means. The circuit includes matching transistors Q ₁ and Q ₂ connected in series with resistors R ₁ and R ₂ respectively. The collector of transistor Q ₂ is connected to the output line 12, and the emitter resistor R ₁ of transistor Q ₁ is connected. There is a three-resistor voltage divider 26, 28, 30, which fixes the base voltages of transistors Q ₁ and Q ₂ at a predetermined level, as explained below.

The return circuit of the operational amplifier 14 has an input terminal 16,
22 at the same potential, the amplifier output voltage
V ₀ can be viewed as the sum of the diode voltage V ₂ and the voltage applied to the non-inverting input terminal. In the bridge type circuit shown in the figure, the voltage at terminal 22 is also the output voltage.
This is not particularly relevant to the present _invention , and other circuits may be used to combine the Zener voltage with the compensation voltage.

The voltage reference output V ₀ can be expressed as a function of circuit element values and parameters described below. This relationship is as described as an addendum in this specification. As stated in this postscript, the output voltage can be expressed as follows.

V ₀ = V ₂ + (R ₂ /R ₁ -1) V _be /1-δ + R ₂ /R ₁ ε…(1
A) In equation (1A), V ₂ is the Zener diode voltage, V _be is the base-emitter voltage (of Q ₁ or Q ₂ ), and δ is the proportionality coefficient of the base voltage of Q ₂ (i.e., V _b2 =
δV ₀ ), ε is the proportionality coefficient of the base voltage of Q ₁ , R ₁ , R ₂
is the resistance value.

To determine a set of relationships for zero temperature compensation, taking the derivative of equation (1A) with respect to temperature,
If it is set to zero, formula (2A) is obtained, R ₁ /R ₂ = 1 + α / γ ... (2A) γ is d / dTV _be approximately equal to (V _G0 - V _bep ), and α is as described above. d/dTV is equal to _Z and V _G0 is the band gap voltage.

If the zero temperature coefficient condition is made even stricter, formula (1A)
becomes as follows.

V ₀ =V _K +α(T-T _K )+(R ₂ /R ₁ -1)(V _G0 -γT)/
1-δ+R ₂ /R ₁ ε...(3A) V _K and T _K are constants {see formula (1)} T is the device temperature If you substitute formula (2A) into formula (3A), formula (4A) is obtained.
is obtained.

V ₀ (α)=V _K +α (V _GO /γ−T _K )/1−δ+ε(1−
α/γ)…(4A) V _K , T _K , δ, ε, γ are constants. If we take the derivative of equation (4A) with respect to α and set it to zero, then V _G0 /V _K −γT _K /V _K = ε/1−δ+ε (5A) If this relationship holds true, V ₀ is unrelated to α. That is, the control circuit is effective in obtaining the desired results regardless of the Zener diode used.

Since the set parameters are valid for any α, the other relationship between ε and δ can be expressed as Equation (4A)
It is obtained by setting α=0 in .

That is, V _K /V ₀ =1−δ+ε …(6A) If ε and δ are calculated from equations (5A) and (6A), ε=(V _G0 −γT _K )/V ₀ …(7A) δ=1+ε− V _K /V ₀ ...(8A) These relations are for zero temperature coefficient at a specified output voltage, but in a similar way, the temperature coefficient can be controlled by making it dependent on adjusting the output voltage to a specified value. Other modified relational expressions can be obtained for other methods. For example, to match the performance of a reference device to other circuit characteristics,
There are applications that require a special non-zero temperature coefficient at a specified reference voltage. Additionally, the control functions described herein may be used where different output voltages are required for individual units within a group, each output voltage having a different corresponding temperature coefficient requirement.

In the case of the circuit of Figure 1 used to obtain the zero temperature coefficient, the values for ε and δ are the experimentally determined values of V _K and T _K , the known value V _G0 , and the calculated value δ.
(obtained by using the known value V _bep in equation (1A)) and the desired value for V ₀ can be obtained by substituting into equations (7A) and (8A). V _K , T _K can be determined experimentally by voltage vs. temperature measurements of a number of embedded Zener diodes; typical values estimated by extrapolation are V _K = 4.74, T _K = -383. It is 〓.
The value of V _bep is 0.655 at T ₀ =300〓.

When V ₀ =10V, the proportionality coefficient is as follows.

ε=0.1960 δ=0.7220 Therefore, by selecting resistors 26, 28, and 30 such that the base voltages V _b1 and V _b2 are 1.960 and 7.220 volts, the circuit of FIG.
The best temperature compensation is obtained when either R ₁ or R ₂ is adjusted to provide the desired output voltage of 10 volts. Which of R ₂ and R ₁ to adjust depends on whether the first measured output voltage is above or below 10 volts.

As mentioned above, for the experimentally measured range of α for a large number of Zener diodes obtained by IC processes, the corresponding values of R ₂ /R ₁ are reasonably practical. Returning to equation (2A) and substituting the value of the measurement range corresponding to the measured Zener voltage V _Z (300〓) 6.0 to 6.6 into the value of α, the minimum R ₂ /R ₁ = 1.966 (when V _Z = 6.0) ) Maximum R ₂ /R ₁ =2.426 (when V _Z =6.6) FIG. 2 shows in detail a preferred embodiment of the voltage reference device including the configuration of FIG. 1 described above.
In FIG. 2, Q ₁₁₂ and Q ₁₁₃ are the basic elements of the operational amplifier 14. The Zener diode D ₂ is Kelvin connected, and its force and sense electrodes are at the same potential. One of these electrodes is connected to the inverting input terminal 16 and the other is connected to the common line 20 through a resistor R ₁₄₃ (18 in FIG. 1).
are connected to each. Transistor Q ₁₁₅ ,
Q ₁₁₆ is connected to Q ₂ and Q ₁ in Figure 1, and resistors R ₁₃₈ and R ₁₃₉ are connected to the first
In addition to the resistors R ₂ and R ₁ in the figure, the resistors R ₁₃₅ , R ₁₃₆ , and R ₁₃₇ are the first
They correspond to resistors 26, 28, and 30 in the figure, respectively.

The second amplifier circuit is configured in a symmetrically balanced manner. Q ₁₀₇ is the collector current Q ₁₁₂ ,
Q ₁₁₃ . The collector of Q ₁₁₄ is
It receives the emitter current of Q ₁₁₂ and Q ₁₁₃ and adjusts it so that the total current is correct. The base of Q ₁₁₄ is controlled by the current from the left collector of Q ₁₀₇ through voltage conversion transistor Q ₁₀₈ and pinch resistor R ₁₄₀ .

Q ₁₀₉ and Q ₁₁₀ are buffer transistors, and Q ₁₀₉
The current of is controlled by Q ₁₀₅ matched with Q ₁₀₄ to give equal currents. The current of Q ₁₀₄ is Q ₁₀₇
The current in Q ₁₀₇ and Q ₁₀₉ flow through Q ₁₀₆ matched with
is equal to the current of Q ₁₂₄ . Therefore, even if there is an error in the base currents of Q ₁₀₉ and Q ₁₀₄ , such error is balanced with respect to Q ₁₁₂ and Q ₁₁₃ , and therefore the error is canceled out due to circuit symmetry.

Q ₁₀₃ carries the additional current required by Q ₁₁₅ and Q ₁₁₆ . Q ₁₁₁ is the output buffer transistor
It is a protection transistor for _Q110 . The emitter on the left side of Q ₁₀₉ helps start the circuit.

FIG. 3 is a graphical diagram illustrating the voltage-temperature relationship described above with respect to FIG. 1, obtaining the best temperature compensation by adjusting the reference output voltage to a specified value. In FIG. 3, two straight lines Z ₁ and Z ₂ indicate the limits of the range of variation for the measured voltage versus temperature characteristic curve of a number of buried Zener diodes. The slopes (α ₁ , α ₂ ) of these lines are the derivatives of the voltage versus temperature relationship described above. If these lines (and lines for intervening data not shown) are extrapolated to the left, they intersect in a common region centered at a particular voltage V _K and a corresponding temperature T _K . (In the case of the measured data provided here, the crossover occurs at temperatures below absolute zero and has no physical correspondence, but is conceptually important.) Due to the common intersection and at least approximately linear characteristics, , the voltage versus current characteristics of the Zener diode of the voltage source can be expressed as described above.

That is, _Vdev = _VK +α(T- _TK ) α is the slope of each curve.

There are also two straight lines J ₁ and J ₂ in FIG. 3, which lines represent the voltage associated with the Zener voltage and which is obtained from the compensation voltage source means 24 with a band gap junction. This indicates the limit of the range of change in the voltage vs. temperature characteristic curve. These lines also intersect in a common area,
The control circuit for the output of the compensated voltage source is arranged so that this common area is located at the temperature T _K , i.e. the Zener characteristic curve
It is configured to be located on the same vertical line as the common area of the intersection of Z ₁ and Z ₂ . The control circuit further aligns the common intersection point with a compensation voltage V _J of such magnitude as to make the resultant voltage of the combination of compensation voltages V _J and V _K equal to a specified reference output voltage, i.e., 10 volts in this case. It is made up of.

Therefore, in this configuration, if the voltage reference device is adjusted to obtain the specified 10 volt output by varying the line slope of the compensation voltage source within the range J ₁ to _{J 2} , the voltage reference device The result is that the slope of the curve J _N is finally adjusted in an inversely matched (ie complementary) relationship to the slope of the characteristic curve Z _o of the basic source Zener diode. Therefore, when the output voltage is adjusted to its predetermined value, the temperature coefficient of the voltage reference device is at its best, at or near zero.

The preferred embodiments of the present invention have been described above, but
This is intended to explain the principles of the invention and is not intended to limit the scope of the invention. The compensation means of the invention can utilize various compensation voltage source means operated from the basic voltage source. Furthermore, various control circuits can be used to supplement the basic idea of the invention. Therefore, from the above description, those skilled in the art will be able to apply the present invention in various ways.

P.S. Since the input terminals of the amplifier 14 are at the same potential, the following equation can be obtained.

V ₀ −V _Z =δV ₀ −V _be −R ₂ /R ₁ (εV ₀ -V _be ) V ₀ −δV ₀ +ε・R ₂ /R ₁・V ₀ =V _Z −V _be +R ₂ /R ₁・V _be V ₀ (1-δ+εR ₂ /R ₁ )=V _Z +(R ₂ /R ₁ -1)V _be V ₀ =V _Z +(R ₂ /R ₁ -1)V _be /1 −δ＋εR ₂ /R ₁ …(1A
) d/dTV ₀ = 1/1-δ+εR ₂ /R ₁ (dV ₂ /dT + (R ₂ /R ₁ -1)dV _be /dT) R ₂ /R ₁ -1=-dV _Z /dT/dV _{If be} /dT V ₂ = V _K + α (T - T _K ), then dV _Z /dT = α V _be = V _G0 -γT, then d/dTV _be = -γ dV _Z /dV _be = -α/ γ R ₂ /R ₁ = 1 + α / γ ... (2A) By substituting V ₂ and R ₂ /R ₁ into equation (1A), V ₀ = V _K + α (T - T _K ) + (α / γ) ( V _g0 −γT)/1−
δ+ε(1+α/γ) If we expand the numerator, V _K −αT _K +α/γV _g0 Therefore, the voltage as a function of α is V ₀ =V _K +α(V ₉₀ /γ−T _K )/1−δ+ε(1+α /
γ) V _K , T _K , δ, ε, γ are constants...(4A) If we take the derivative with respect to α, dV ₀ /dα=[1-δ+ε+ε/γα](V ₉₀
/γ−T _K )−[V _K −α(V ₉₀ /γ−T _K )]ε/γ/[1
−δ+ε(1+α/γ)] ^2If we set this to zero, V _g0 /V _K −γ・T _K /V _K =ε/1−δ+ε …(5A)

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the basic configuration of a preferred embodiment of the present invention, FIG. 2 is a circuit diagram showing details of a voltage reference device based on the principle shown in FIG. 1, and FIG. 3 is a circuit diagram showing the voltage of a voltage source. FIG. 3 is a graph diagram showing temperature characteristics. In addition, in the symbols used in the drawings, 10... Zener diode voltage source, 12... Output line, 1
4...Operation amplifier, 16...Inverting input terminal, 18
...Resistor, 20...Common line, 22...Non-inverting input terminal, 24...Compensation voltage means (control circuit),
26, 28, 30...Voltage dividing resistor, R ₁ , R ₂ , R ₁₃₅
~ _R143 ...resistor, _Q1 , _Q2 , _Q103 ~ _Q116 ...transistor.

Claims (1)

[Scope of Claims] 1. A first voltage source means for generating a first voltage according to a voltage-versus-temperature characteristic curve having a first slope; and a second voltage source means generating a first voltage according to a voltage-versus-temperature characteristic curve having a second slope. a second voltage source means for generating a second voltage, the second voltage being combined with the first voltage to generate a composite reference output voltage responsive to the first and second voltages; control circuit means operative in conjunction with the voltage source means, the control circuit means controlling the slope of the voltage versus temperature characteristic curve of the second voltage source means in accordance with predetermined parameters of elements of the control circuit means. means for controlling each of two independent curve shapes including as one of the shapes; adjustable means for varying the second voltage and correspondingly varying the composite reference voltage; The second voltage is varied in order to impart a predetermined temperature coefficient to the composite voltage in association with the predetermined parameter when the second voltage is preselected from a wide possible range and adjusted to a particularly specified value. means for varying said second slope under the control of said adjustable means as the voltage is increased. 2. The control circuit means is operative to provide an effective zero temperature coefficient to the composite voltage when the composite voltage reaches the specified value. Temperature compensated solid state voltage reference device. 3. The control circuit means is operative to create an effective inversion match between the two slopes when the composite voltage reaches the specified value, and to perform zero temperature compensation at the specified value. A temperature compensated solid state voltage reference device according to claim 2. 4. The first voltage source means comprises a Zener diode, and the second voltage source means comprises means for generating a compensation voltage that is a function of the base-emitter voltage of the semiconductor junction. A temperature compensated solid state voltage reference device according to claim 1. 5. The temperature compensated solid state voltage reference device of claim 4, wherein said adjustment means includes a variable resistor in series with said junction. 6. A first voltage of the solid-state voltage source is connected to a second voltage source means for generating a second voltage, and a composite reference voltage corresponding to the sum of the first and second voltages is obtained. In the technique of temperature compensation by generating a selectable wide range, the voltage versus temperature characteristic curves of the two voltages have opposite signs so that temperature effects tend to be canceled at the reference voltage. A method of providing temperature compensation for said reference voltage of a certain value specified from a range, said method comprising: adjusting said characteristic curve of said second voltage source means according to predetermined parameters of an element of said control circuit means; connecting to said second voltage source means control circuit means for controlling each of two independent curve shapes including a slope as one of the shapes; controlling the slope of a voltage-temperature characteristic curve of the second voltage by adjusting the circuit elements; and a predetermined relationship between the effects on the reference voltage due to the temperature characteristics of the first and second voltages, such that when the reference voltage is adjusted to the specified value, a predetermined temperature with respect to the reference voltage is generated. A reference voltage temperature compensation method characterized by providing a coefficient.