CA1141820A - Temperature compensated ic voltage reference - Google Patents
Temperature compensated ic voltage referenceInfo
- Publication number
- CA1141820A CA1141820A CA000336481A CA336481A CA1141820A CA 1141820 A CA1141820 A CA 1141820A CA 000336481 A CA000336481 A CA 000336481A CA 336481 A CA336481 A CA 336481A CA 1141820 A CA1141820 A CA 1141820A
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- Prior art keywords
- voltage
- source
- temperature
- slope
- curve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/08—Regulating voltage or current wherein the variable is dc
- G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
- G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
- G05F3/18—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using Zener diodes
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
- G05F1/567—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for temperature compensation
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Automation & Control Theory (AREA)
- Nonlinear Science (AREA)
- Continuous-Control Power Sources That Use Transistors (AREA)
- Control Of Electrical Variables (AREA)
- Amplifiers (AREA)
Abstract
935.037 ABSTRACT OF THE DISCLOSURE
A temperature-compensated IC voltage reference comprising a Zener diode serving as the principal voltage source, in combination with a compensating voltage source including a transistor providing a forward-biased junction, and control circuitry. The compensating voltage is summed with the Zener voltage to produce a reference voltage. The compensating voltage source includes an adjustment element for trimming the reference output to a specified voltage, and the control circuitry operates with that adjustment element to automatically produce optimum temperature compensation when the output has been adjusted to the specified value.
A temperature-compensated IC voltage reference comprising a Zener diode serving as the principal voltage source, in combination with a compensating voltage source including a transistor providing a forward-biased junction, and control circuitry. The compensating voltage is summed with the Zener voltage to produce a reference voltage. The compensating voltage source includes an adjustment element for trimming the reference output to a specified voltage, and the control circuitry operates with that adjustment element to automatically produce optimum temperature compensation when the output has been adjusted to the specified value.
Description
935.037 - 1~418~0 BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to solid-state voltage refer-ences. More particularly, this invention relates to improved means and methods for temperature-compensating such voltage ref-- erences, and to simplified procedures by which such references may be set for optimum compensation performance.
Description of the Prior Art Solid-state voltage references commonly incorporate a junction voltage source, such as a Zener, which exhibits a signi-ficant temperature coefficient requiring compens~tion. For manyreference devices, the voltage-vs-temperature relationship can - be approximated as:
Vdev = VK + C~(T - TK) Eq. 1 where Vdev is the device terminal voltage at any temperture T, VK and TK are constants, and Cis a coefficient which varies with the processing of the device.
To provide compensation for the changes in voltage - 20 with temperature, the output of such a device can be summed with a compensating valta~ c~rcuit, such as a band-gap junction source, having a temperature coefficient opposite to the origi-nal in sign (slope), and incorporating appropriate scaling to 935.037 1~4~;aO
develop the specified output voltage level. The characteristics of such a compensated voltage reference device may be represented by the following relationship:
Vref = ~ [(VGO -~ T~ ~ + VK + C~(T -TK)] Eq. 2 where VGo is the band-gap voltage, ~ is the temperature coefficient of a forward-biased junction,~J~is a proportionality factor between the voltage reference device and the compensating device, and ~ is an over-all scaling factor needed to achieve a specified voltage vllue.
Such a device has two degrees of freedom for adjust-ment purposes, represented symbolically by ~J (slope) and ~
(scaling) in Equation (2) above. One procedure in adjusting the device for specified operating characteristics is to utilize a computer-operated algorithm to set crat the proper value to minimize temperature-induced variations for a cal^ulated value ofOC, and then adjust ~ to achieve the specified output voltage Vref~. This proceaure accordingly requires two separate adiust-ment steps, one for each of the two degrees of freedom of the control circuit design Experience has shown however that this procedure is undesirably complex and expensive to carry out, and although useful commercially, it is not full~ satisfactory in achieving desired performance. Thus a need for significant ;~ 25 improvement has become evident.
935.037 1~41t~ZO
SUMMARY OF THE I~VENTION
In accordance with an important aspect of the present invention, it has been found that importantly superior results can be achieved by a technique wherein adjustment of a single circuit element of the voltage reference is employed to simul-taneously alter the two variable factors (represented by ~ and ~r in Equation 2) which control the ou~put voltage and temper-ature characteristics of the voltage reference. More particu-larly, in a presently preferred embodiment of the invention, the adjustment of a trim resistor to bring the reference output voltage to the specified value servés concurrently to alter the temperature compensating control circuitry to provide for optimum TC at the point where the reference voltage output is equal to the specified value.
To put the matter somewhat differently, it has been discovered that the two degrees of freedom previously utilized to make the complete adjustment of each voltage reference should be reduced to a single degree of freedom, thereby to improve per-formance of the voltage reference and at the same time simplify the manufacturing procedures. ~educing the adjustment procedure to a single degree of freedom can be understood in a mathematical sense ~y considering that the variable ~ is made dependent upon ~r by the topology of the associated control circuitry for the - compensating voltage source. The dependency relationship can be 935.037 ~4~0 expressed as follows:
~ = Vref' Eq 3 where Vref' is the specified output voltage.
The output voltage can then be expressed as:
VK + ~rVGO -ocTK [(VGO ~ T)~r+ VK +Oc(T-The final expression becomes:
ref Vref' GOV K ~TK + (~ ~rIT
where ~ris the remaining adjustable parameter.
~ In accordance with one important aspect of the inven-tion, adjustment of Vref to the specified value simultaneously ma~es the term (OC - ~ ~r ) zero, i.e. by setting ~ ~r =CX~, !
thus establishing the desired equality within the limits of the model. i, Other objects, aspects and advantag~s of the invention will in part be pointed out in, and in part apparent from, the following description of the preferred em~odiment considered to-gether with the fol~owing drawings.
BRIEF DESCRIPTION OF T~E DRAW~NGS
FIGURE 1 is a simplified circuit diagram to illustrate the basic arrangement of a preferred embodiment of the invention, FIGURE 2 is a circuit diagram showing details of a voltage reference based on the principles illustrated in Figure - l; and FIGURE 3 is a graph showing voltage-vs-temperature characteristics of classes of voltage sources.
~ETAILED DESCRIPTION OF
A PREFERRED EMBODIME~T
Turning now to Figure 1, the voltage reference in accordance with the principles of this invention includes a Zener diode voltage source 10 with one electrode connected to the output line 12 of an operational amplifier 14. The diode is connected through a negative feedback circuit to the 0 inverting input terminal 16 of the amplifier, which in turn is connected through a resistor 18 to a common line or ground 20.
The Zener diode 10 is formed as part of an IC chip, together with associated control circuitry as shown in Figure 1~ 2. The chip also typically will include further circuitry (not shown) requiring the stabilized reference voltage to be developed as will be explained. Preferably, the Zener diode is formed as a buried-layer device, for example as disclosed in detail in U.S. Patent ~o. 4,136,349 issued January 23, 1979 to W.K Tsang, and assigned to the assignee of this applica-tion.
The potential of the non-inverting terminal 22 of the amplifier 14 is fixed by a control circuit generally in-dicated at 24 comprising a second voltage source means. This circuit includes series-connected matched transistors Ql and Q2 each 935.037 1~4~8ZO
with an emitter resistor Rl and R2. The collector of Q2 is connected to the output line 12, and the emltter resistor Rl is returnea to ground. A 3-resistor voltage divider 26, 28, 30 is provided to fix t'ne base voltages of transistors Ql and Q2 at predetermined levels as will be explained.
The feedback circuit of the operational amplifier 14 maintains the input terminals 16 and 22 at the same potential, so that the amplifier output voltage VO can be viewed as being ~ff /~C~
`~`r` the sum of the diode voltage Vz and the voltage supplcd to the non-inverting terminal 22 It may be noted that in the particu-lar bridge-type of circuit shown herein, the voltage on terminal 22 also is dependent upon the output voltage VO However, such dependency is not a requirement of the invention, and other types of circuitry can be used to combine the Zener voltage with a compensating voltage.
The voltage reference output VO can be represented as a function of circuit element values and significant parameters to be discussed subsequently. A detailed derivation of the relationship is set fOrth in the Appendix at the end of this specification. As shown in that derivation, the output voltage can be expressed as:
R
Vz + (Rl ~ 13 Vbe 1 - ~ + ~ ~ Eq. lA
where Vz is the Zener diode voltage, V~e is the base-to-emitter voltage (of either Ql or Q2)' ~41~ 935.037 is the proportionality factor for the base ge of Q2 (i-e~ Vb2 = ~ VO)~ ~ is the pro-portionality factor for the base voltage of Ql~
and ~1~R2 are resistance values.
To determine one set of relationships for zero TC, the derivative of Equation lA can be taken with respect to temperature, and set to zero, to produce:
Rl = 1 + C~X~ Eq. 2A
where ~ is defined as ddT Vbe which is approxi-mately equal to (VG0 ~ VbeO?/To 0C, as prev o y described is equal to dT Vz; and VGo is the band-gap voltage.
To develop the necessary further constraints for zero TC conditions, Equation lA may be further elaborated as:
V = K ( TK ) + ~ ~ - 1 ) ( VG0 - ~ T) Eq~ 3A
where VK and TK are constants (see Eq. 1 a~ove~ .
and T is the device temperature.
Equation 3A can be further developed through use of Equation 2A to produce:
V (oC) K ~ C~ TK) ~q. 4A
where VK, TK, ~, ~ and b' are constants 9~5.037 1:14i~
Taking the derivative of Equation 4A with respect to GC and setting it equal to zero yields:
VK ~ VK 1 - ~ + ~ Eq 5A
W~en this relationship is esta~lished, VO will be independent of ~ . That is, the control circuitry will be effective in achieving the desired result regardless of the particular Zener diode with which it is used.
Since the parameters being established are to be valid for any~, a still further relationship for ~ and ~ i can be found by setting C~ = O in Equation 4A:
vK = 1 - ~ ~ Eq. 6A
o Equations SA and 6A can be solved for ~ and ~ :
= (VG0 ~ TK)/Vo Eq. 7A
= 1 + ~ _ VK
VO Eq. 8A
These relationships have been derived to provide for zero TC at the specified output ~oltage. However, modified re-lationships can, by the same techniques, be derived for other kinas of desired control of the temperature coefficient dependent upon adjusting the output voltage to a specified value. For example, there are applications requiring a specific non-zero TC at the specified reference voltage, e.g. for the purpose of 935.037 1~418XO
matching the reference performance to another circuit character-istic. In addition, the control function described herein can be used in applications where different output voLtages are required for individual units of a group, wi_h each such output voltage having a corresponding different TC requirement. Thus, the manner in which the invention is embodied will depend upon the particular application problem to be soLved.
.
In the case of the Figure 1 circuit to be used to achieve æero TC, the numerical values for ~ and S can be ob-tained by inserting into Equation 7A and 8A experimentallydetermined values for VK and TK, together with the known value of VGo~ a calculated value for ~ (using the definition in Equation lA with a known value of Vbeo), and the desired value for VO VK and TK have been determined experimentally by voltage-vs-temperature measurements on a large number of buried Zener diodes, and typical extrapolated values are: VK = 4.74 and TK = -383K. The value of VbeO is 0.655 at To = 300K.
Using a specified value VO = 10, the proportionality factors ~ecome:
~- = .1960 S = .7220 Accordingly, by corresponding selection of the resis-tors 26, 28 and 30 to achieve base voltages Vbl and Vb2 of 1.960 and 7.220 volts, the circuit arrangement of Figure 1 will provide optimum temperature compensation when one or the other emitter resistor Rl or R2 has been adjusted to achieve the specified output voltage of 10 volts. Which resistor R2 or ~1 is trimmed depends upon whether the initially measured output voltage is 935.037 ~4~
For an experimentally measured range ofCC for a large number of uni~s of the class of Zener aiodes produced -~ith a~
IC process, as described hereina~ove, the corresponding values of R2/~1 are appropriately practical. ~everting to Eguation 2A, and substituting the measured range of values for ~ correspond-ing to measured Zener voltages of Vz (at 300~K) of 6.0 to 6.6, it is found that:
minimum ~2/Rl = 1.966 (for Vz = 6.0) ~2/~1 = 2.426 (for Vz = 6.6) Figure 2 shows details of a presently preferred voltage reference incorporating the arrangement of Figure 1, and which performs as described above. In Figure 2, Ql-2 and Q113 form the basic elements of the operational amplifier 14. The Zener diode Dz has Kelv1n connections, with force and sense electrodes essentially at the same potential. One is connected to inverting input terminal 16 and the other is connected through a resistor R143 ~reference 18 in Figure 1) to common-line 20r ~ransistors Q115 and Q116 correspond to Q2 and Ql of Figure 1, resistors ~138 and ~139 correspond to resistors R2, ~1~ and resistors ~135 ~36 and R137 correspond to resistors 26, 28 and 30.
The amplifier circuitry of ~igure 2 is arranged with an essentially symmetrical balanced configuration. Q107 supplies collector current to Q11~ and Q113 The collector of Q~14 receives the emitter currents of Q112 and Q113~ and provides 1~41820 adjustment to make the to.al current correct. The base of Q114 is controlled through voltage translation transistor Q108 and pinch resistor ~140 by current from the left-hand collector of Qlog and Qllo are buffer transistors. The current in Qlog is controlled-by Q105 which is matched to Q104 to provide for equal currents. The ~104 current passes through Q106 which is matched to Q107' 50 that the Q107 current and the Qlog cur-rent will be equal, and equal to the Q114 current. Thus, although the base currents of Qlog and Q114 may represent errors, such errors are balanced with respect to Q112~ Q113~ so that they tend to cancel due to thP circuit symmetry.
Q103 carries any additional current required by Q115 Q116 Qlll provides protection for the output buffer Qllo.
The left-hand emitter of Qlog serves to aid start-up of the circuitry.
Figure 3 illustrates graphically the voltage ana tem-perature relationships discussed a~ove with reference to Figure 1, for achieving optimum temperature compensation through adjust-ment of the reference output voltage to its specified value.The presentation includes two straight lin~s Zl and Z2 represent-ing the outer limits of the range of variation for measured voltage-vs-temperature characteristic curves of a large number of buried ~ener diodes~ The slope of these lines (~1 andOC 2 1~4~0 represent the derivative of the voltage-vs-temperature relation-ship as discussed above~ Extrapolation of these lines (and lines for intervening data, not shown) to the left results in an inter-section in a common region centered about a particular voltage VK and a corresponding temperature T~. (Note: For the measured data presented herein, the intersection occurs at a temperature below absolute zero, and thus has no physical counterpart, but does have conceptual significance.) With a common intersection point, and at least approximately straight-line characteristics, the voltage-vs-temperature characteristics of this Zener-diode class of voltage sources can be represented, as previously stated, as:
Vdev = VK + CC(T - TK) wherecCrepresents the slope of each curve.
' Also shown on.Figure 3 are two additional straight lines J1 and 32 representing limits of the range of voltage-vs-temperature characteristic curves for the voltage which is com-bined with the Zener voltage, and whic7n is derived from the compensatins voltage source means 24 comprising a band-gap junction. These lines also intersect at a common region, and the control circuitry of the compensating voltage source means is arranged to locate this common region at a temperature of TK, i, e~ on the same vertical line as the common region of intersection of the Zener characteristic curves Zl and Z2^ T~e control circuitry is further arranged to locate the common inter-section at the compensating voltage V3 having a magnitude such ~4~ 935.037 that when VJ is combined with VK, the composite voltage will be equal to the specified reference output voltage, i.e in this case 10 volts.
Accordingly, with this arrangement the adjustment of the voltage reference to provide a specified output of 10 volts, ~y in effect changing the slope of the compensating voltage source line within the range between Jl and J2~ will automatically result in the final adjusted slope of the curve JN having an inversely matching (i.e., complementary~ relationship with respect to the slope of the characteristic curve line Z~ of the particular Zener diode forming the basic source of the vo}tage reference. Thus, the temperature coefficient of the voltage reference will be optimized at or very near zero, as a result of trimming the output voltage to its specified value.
Although a specific preferred embodiment of the in-vention has been set forth hereinabove in detail, i_ is desired to emphasize that this is for the purpose of illustrating the principles of the invention, and is not to be considered in limitation of the scope of the invention. ~hus it will be understood that the invention can be used to compensate various ', types o~ basic voltage sources, and that the compensation means can utilize various kinds of compensating voltage source means to be operated with the basic voltage source Moreover, a wide variety of control circuits can be employed to implement the basic concepts of the invention~ Accordingly, it will be appre-935.037 114i820 ciated that the present disclosure is provided to aid those skilled in this art in adapting the invention in various forms best suited to particular applications.
~418aO
APPENDIX
Since the input terminals of the amplifier 14 are at the same potential, the following equality can be written:
Vo - Vz = ~?Vo ~ Vbe ~ Rl ( ~ Vo ~ Vbe) V - ~V + ~ VO - Vz ~ Vbe + ~ be Vo ( 1- ~; + ~ ~) = Vz + ~ - 1) Vbe V + ( R2 1 ) V
1 - ~ + ~ g~ Eq. lA
dT 1 - S + ~ ~ 1 dVz + (~ - 1) be ]
R2 _ 1 = ~ dVz/dT where dV~ = O
Rl dVbe/dT dT
~2 = 1 _ dVz~dT
Rl dVbe,/dT
let Vz = VK + C~ ( T -TK~ I
dVz = cX~ ;
dT
let Vbe = VGO ~
dT Vbe dVz = c~C
dVbe R2 -- 1 +
Rl ~ E~. 2A
~1418~aO
Substituting in Eq. lA for Vz and R2,~Rl gives:
Vo = VK + C~(T - TK) + (~)(Vqo - ~) T) 1 - ~ + ~(1 + ~) expanding the numerator gives:
VK - ~ TK + ~ Vgo so the voltage as a function of cx_ is:
V VK +CX~ ~ -TK) VK, TK, ~ = constants Eq. 4A
1 - S + ~(1 + ~ ) Taking the derivative with respect toC~gives:
~ + ~ + - c~]( ~ ~ TK) ~ [VK
d ~C 2 [ 1 -~+ ~, (1 + ~)]
Setting the derivative equal to zero and solving yields:
.vV~ ~ VK 1 - ~ + ~ Eq. 5A
Field of the Invention This invention relates to solid-state voltage refer-ences. More particularly, this invention relates to improved means and methods for temperature-compensating such voltage ref-- erences, and to simplified procedures by which such references may be set for optimum compensation performance.
Description of the Prior Art Solid-state voltage references commonly incorporate a junction voltage source, such as a Zener, which exhibits a signi-ficant temperature coefficient requiring compens~tion. For manyreference devices, the voltage-vs-temperature relationship can - be approximated as:
Vdev = VK + C~(T - TK) Eq. 1 where Vdev is the device terminal voltage at any temperture T, VK and TK are constants, and Cis a coefficient which varies with the processing of the device.
To provide compensation for the changes in voltage - 20 with temperature, the output of such a device can be summed with a compensating valta~ c~rcuit, such as a band-gap junction source, having a temperature coefficient opposite to the origi-nal in sign (slope), and incorporating appropriate scaling to 935.037 1~4~;aO
develop the specified output voltage level. The characteristics of such a compensated voltage reference device may be represented by the following relationship:
Vref = ~ [(VGO -~ T~ ~ + VK + C~(T -TK)] Eq. 2 where VGo is the band-gap voltage, ~ is the temperature coefficient of a forward-biased junction,~J~is a proportionality factor between the voltage reference device and the compensating device, and ~ is an over-all scaling factor needed to achieve a specified voltage vllue.
Such a device has two degrees of freedom for adjust-ment purposes, represented symbolically by ~J (slope) and ~
(scaling) in Equation (2) above. One procedure in adjusting the device for specified operating characteristics is to utilize a computer-operated algorithm to set crat the proper value to minimize temperature-induced variations for a cal^ulated value ofOC, and then adjust ~ to achieve the specified output voltage Vref~. This proceaure accordingly requires two separate adiust-ment steps, one for each of the two degrees of freedom of the control circuit design Experience has shown however that this procedure is undesirably complex and expensive to carry out, and although useful commercially, it is not full~ satisfactory in achieving desired performance. Thus a need for significant ;~ 25 improvement has become evident.
935.037 1~41t~ZO
SUMMARY OF THE I~VENTION
In accordance with an important aspect of the present invention, it has been found that importantly superior results can be achieved by a technique wherein adjustment of a single circuit element of the voltage reference is employed to simul-taneously alter the two variable factors (represented by ~ and ~r in Equation 2) which control the ou~put voltage and temper-ature characteristics of the voltage reference. More particu-larly, in a presently preferred embodiment of the invention, the adjustment of a trim resistor to bring the reference output voltage to the specified value servés concurrently to alter the temperature compensating control circuitry to provide for optimum TC at the point where the reference voltage output is equal to the specified value.
To put the matter somewhat differently, it has been discovered that the two degrees of freedom previously utilized to make the complete adjustment of each voltage reference should be reduced to a single degree of freedom, thereby to improve per-formance of the voltage reference and at the same time simplify the manufacturing procedures. ~educing the adjustment procedure to a single degree of freedom can be understood in a mathematical sense ~y considering that the variable ~ is made dependent upon ~r by the topology of the associated control circuitry for the - compensating voltage source. The dependency relationship can be 935.037 ~4~0 expressed as follows:
~ = Vref' Eq 3 where Vref' is the specified output voltage.
The output voltage can then be expressed as:
VK + ~rVGO -ocTK [(VGO ~ T)~r+ VK +Oc(T-The final expression becomes:
ref Vref' GOV K ~TK + (~ ~rIT
where ~ris the remaining adjustable parameter.
~ In accordance with one important aspect of the inven-tion, adjustment of Vref to the specified value simultaneously ma~es the term (OC - ~ ~r ) zero, i.e. by setting ~ ~r =CX~, !
thus establishing the desired equality within the limits of the model. i, Other objects, aspects and advantag~s of the invention will in part be pointed out in, and in part apparent from, the following description of the preferred em~odiment considered to-gether with the fol~owing drawings.
BRIEF DESCRIPTION OF T~E DRAW~NGS
FIGURE 1 is a simplified circuit diagram to illustrate the basic arrangement of a preferred embodiment of the invention, FIGURE 2 is a circuit diagram showing details of a voltage reference based on the principles illustrated in Figure - l; and FIGURE 3 is a graph showing voltage-vs-temperature characteristics of classes of voltage sources.
~ETAILED DESCRIPTION OF
A PREFERRED EMBODIME~T
Turning now to Figure 1, the voltage reference in accordance with the principles of this invention includes a Zener diode voltage source 10 with one electrode connected to the output line 12 of an operational amplifier 14. The diode is connected through a negative feedback circuit to the 0 inverting input terminal 16 of the amplifier, which in turn is connected through a resistor 18 to a common line or ground 20.
The Zener diode 10 is formed as part of an IC chip, together with associated control circuitry as shown in Figure 1~ 2. The chip also typically will include further circuitry (not shown) requiring the stabilized reference voltage to be developed as will be explained. Preferably, the Zener diode is formed as a buried-layer device, for example as disclosed in detail in U.S. Patent ~o. 4,136,349 issued January 23, 1979 to W.K Tsang, and assigned to the assignee of this applica-tion.
The potential of the non-inverting terminal 22 of the amplifier 14 is fixed by a control circuit generally in-dicated at 24 comprising a second voltage source means. This circuit includes series-connected matched transistors Ql and Q2 each 935.037 1~4~8ZO
with an emitter resistor Rl and R2. The collector of Q2 is connected to the output line 12, and the emltter resistor Rl is returnea to ground. A 3-resistor voltage divider 26, 28, 30 is provided to fix t'ne base voltages of transistors Ql and Q2 at predetermined levels as will be explained.
The feedback circuit of the operational amplifier 14 maintains the input terminals 16 and 22 at the same potential, so that the amplifier output voltage VO can be viewed as being ~ff /~C~
`~`r` the sum of the diode voltage Vz and the voltage supplcd to the non-inverting terminal 22 It may be noted that in the particu-lar bridge-type of circuit shown herein, the voltage on terminal 22 also is dependent upon the output voltage VO However, such dependency is not a requirement of the invention, and other types of circuitry can be used to combine the Zener voltage with a compensating voltage.
The voltage reference output VO can be represented as a function of circuit element values and significant parameters to be discussed subsequently. A detailed derivation of the relationship is set fOrth in the Appendix at the end of this specification. As shown in that derivation, the output voltage can be expressed as:
R
Vz + (Rl ~ 13 Vbe 1 - ~ + ~ ~ Eq. lA
where Vz is the Zener diode voltage, V~e is the base-to-emitter voltage (of either Ql or Q2)' ~41~ 935.037 is the proportionality factor for the base ge of Q2 (i-e~ Vb2 = ~ VO)~ ~ is the pro-portionality factor for the base voltage of Ql~
and ~1~R2 are resistance values.
To determine one set of relationships for zero TC, the derivative of Equation lA can be taken with respect to temperature, and set to zero, to produce:
Rl = 1 + C~X~ Eq. 2A
where ~ is defined as ddT Vbe which is approxi-mately equal to (VG0 ~ VbeO?/To 0C, as prev o y described is equal to dT Vz; and VGo is the band-gap voltage.
To develop the necessary further constraints for zero TC conditions, Equation lA may be further elaborated as:
V = K ( TK ) + ~ ~ - 1 ) ( VG0 - ~ T) Eq~ 3A
where VK and TK are constants (see Eq. 1 a~ove~ .
and T is the device temperature.
Equation 3A can be further developed through use of Equation 2A to produce:
V (oC) K ~ C~ TK) ~q. 4A
where VK, TK, ~, ~ and b' are constants 9~5.037 1:14i~
Taking the derivative of Equation 4A with respect to GC and setting it equal to zero yields:
VK ~ VK 1 - ~ + ~ Eq 5A
W~en this relationship is esta~lished, VO will be independent of ~ . That is, the control circuitry will be effective in achieving the desired result regardless of the particular Zener diode with which it is used.
Since the parameters being established are to be valid for any~, a still further relationship for ~ and ~ i can be found by setting C~ = O in Equation 4A:
vK = 1 - ~ ~ Eq. 6A
o Equations SA and 6A can be solved for ~ and ~ :
= (VG0 ~ TK)/Vo Eq. 7A
= 1 + ~ _ VK
VO Eq. 8A
These relationships have been derived to provide for zero TC at the specified output ~oltage. However, modified re-lationships can, by the same techniques, be derived for other kinas of desired control of the temperature coefficient dependent upon adjusting the output voltage to a specified value. For example, there are applications requiring a specific non-zero TC at the specified reference voltage, e.g. for the purpose of 935.037 1~418XO
matching the reference performance to another circuit character-istic. In addition, the control function described herein can be used in applications where different output voLtages are required for individual units of a group, wi_h each such output voltage having a corresponding different TC requirement. Thus, the manner in which the invention is embodied will depend upon the particular application problem to be soLved.
.
In the case of the Figure 1 circuit to be used to achieve æero TC, the numerical values for ~ and S can be ob-tained by inserting into Equation 7A and 8A experimentallydetermined values for VK and TK, together with the known value of VGo~ a calculated value for ~ (using the definition in Equation lA with a known value of Vbeo), and the desired value for VO VK and TK have been determined experimentally by voltage-vs-temperature measurements on a large number of buried Zener diodes, and typical extrapolated values are: VK = 4.74 and TK = -383K. The value of VbeO is 0.655 at To = 300K.
Using a specified value VO = 10, the proportionality factors ~ecome:
~- = .1960 S = .7220 Accordingly, by corresponding selection of the resis-tors 26, 28 and 30 to achieve base voltages Vbl and Vb2 of 1.960 and 7.220 volts, the circuit arrangement of Figure 1 will provide optimum temperature compensation when one or the other emitter resistor Rl or R2 has been adjusted to achieve the specified output voltage of 10 volts. Which resistor R2 or ~1 is trimmed depends upon whether the initially measured output voltage is 935.037 ~4~
For an experimentally measured range ofCC for a large number of uni~s of the class of Zener aiodes produced -~ith a~
IC process, as described hereina~ove, the corresponding values of R2/~1 are appropriately practical. ~everting to Eguation 2A, and substituting the measured range of values for ~ correspond-ing to measured Zener voltages of Vz (at 300~K) of 6.0 to 6.6, it is found that:
minimum ~2/Rl = 1.966 (for Vz = 6.0) ~2/~1 = 2.426 (for Vz = 6.6) Figure 2 shows details of a presently preferred voltage reference incorporating the arrangement of Figure 1, and which performs as described above. In Figure 2, Ql-2 and Q113 form the basic elements of the operational amplifier 14. The Zener diode Dz has Kelv1n connections, with force and sense electrodes essentially at the same potential. One is connected to inverting input terminal 16 and the other is connected through a resistor R143 ~reference 18 in Figure 1) to common-line 20r ~ransistors Q115 and Q116 correspond to Q2 and Ql of Figure 1, resistors ~138 and ~139 correspond to resistors R2, ~1~ and resistors ~135 ~36 and R137 correspond to resistors 26, 28 and 30.
The amplifier circuitry of ~igure 2 is arranged with an essentially symmetrical balanced configuration. Q107 supplies collector current to Q11~ and Q113 The collector of Q~14 receives the emitter currents of Q112 and Q113~ and provides 1~41820 adjustment to make the to.al current correct. The base of Q114 is controlled through voltage translation transistor Q108 and pinch resistor ~140 by current from the left-hand collector of Qlog and Qllo are buffer transistors. The current in Qlog is controlled-by Q105 which is matched to Q104 to provide for equal currents. The ~104 current passes through Q106 which is matched to Q107' 50 that the Q107 current and the Qlog cur-rent will be equal, and equal to the Q114 current. Thus, although the base currents of Qlog and Q114 may represent errors, such errors are balanced with respect to Q112~ Q113~ so that they tend to cancel due to thP circuit symmetry.
Q103 carries any additional current required by Q115 Q116 Qlll provides protection for the output buffer Qllo.
The left-hand emitter of Qlog serves to aid start-up of the circuitry.
Figure 3 illustrates graphically the voltage ana tem-perature relationships discussed a~ove with reference to Figure 1, for achieving optimum temperature compensation through adjust-ment of the reference output voltage to its specified value.The presentation includes two straight lin~s Zl and Z2 represent-ing the outer limits of the range of variation for measured voltage-vs-temperature characteristic curves of a large number of buried ~ener diodes~ The slope of these lines (~1 andOC 2 1~4~0 represent the derivative of the voltage-vs-temperature relation-ship as discussed above~ Extrapolation of these lines (and lines for intervening data, not shown) to the left results in an inter-section in a common region centered about a particular voltage VK and a corresponding temperature T~. (Note: For the measured data presented herein, the intersection occurs at a temperature below absolute zero, and thus has no physical counterpart, but does have conceptual significance.) With a common intersection point, and at least approximately straight-line characteristics, the voltage-vs-temperature characteristics of this Zener-diode class of voltage sources can be represented, as previously stated, as:
Vdev = VK + CC(T - TK) wherecCrepresents the slope of each curve.
' Also shown on.Figure 3 are two additional straight lines J1 and 32 representing limits of the range of voltage-vs-temperature characteristic curves for the voltage which is com-bined with the Zener voltage, and whic7n is derived from the compensatins voltage source means 24 comprising a band-gap junction. These lines also intersect at a common region, and the control circuitry of the compensating voltage source means is arranged to locate this common region at a temperature of TK, i, e~ on the same vertical line as the common region of intersection of the Zener characteristic curves Zl and Z2^ T~e control circuitry is further arranged to locate the common inter-section at the compensating voltage V3 having a magnitude such ~4~ 935.037 that when VJ is combined with VK, the composite voltage will be equal to the specified reference output voltage, i.e in this case 10 volts.
Accordingly, with this arrangement the adjustment of the voltage reference to provide a specified output of 10 volts, ~y in effect changing the slope of the compensating voltage source line within the range between Jl and J2~ will automatically result in the final adjusted slope of the curve JN having an inversely matching (i.e., complementary~ relationship with respect to the slope of the characteristic curve line Z~ of the particular Zener diode forming the basic source of the vo}tage reference. Thus, the temperature coefficient of the voltage reference will be optimized at or very near zero, as a result of trimming the output voltage to its specified value.
Although a specific preferred embodiment of the in-vention has been set forth hereinabove in detail, i_ is desired to emphasize that this is for the purpose of illustrating the principles of the invention, and is not to be considered in limitation of the scope of the invention. ~hus it will be understood that the invention can be used to compensate various ', types o~ basic voltage sources, and that the compensation means can utilize various kinds of compensating voltage source means to be operated with the basic voltage source Moreover, a wide variety of control circuits can be employed to implement the basic concepts of the invention~ Accordingly, it will be appre-935.037 114i820 ciated that the present disclosure is provided to aid those skilled in this art in adapting the invention in various forms best suited to particular applications.
~418aO
APPENDIX
Since the input terminals of the amplifier 14 are at the same potential, the following equality can be written:
Vo - Vz = ~?Vo ~ Vbe ~ Rl ( ~ Vo ~ Vbe) V - ~V + ~ VO - Vz ~ Vbe + ~ be Vo ( 1- ~; + ~ ~) = Vz + ~ - 1) Vbe V + ( R2 1 ) V
1 - ~ + ~ g~ Eq. lA
dT 1 - S + ~ ~ 1 dVz + (~ - 1) be ]
R2 _ 1 = ~ dVz/dT where dV~ = O
Rl dVbe/dT dT
~2 = 1 _ dVz~dT
Rl dVbe,/dT
let Vz = VK + C~ ( T -TK~ I
dVz = cX~ ;
dT
let Vbe = VGO ~
dT Vbe dVz = c~C
dVbe R2 -- 1 +
Rl ~ E~. 2A
~1418~aO
Substituting in Eq. lA for Vz and R2,~Rl gives:
Vo = VK + C~(T - TK) + (~)(Vqo - ~) T) 1 - ~ + ~(1 + ~) expanding the numerator gives:
VK - ~ TK + ~ Vgo so the voltage as a function of cx_ is:
V VK +CX~ ~ -TK) VK, TK, ~ = constants Eq. 4A
1 - S + ~(1 + ~ ) Taking the derivative with respect toC~gives:
~ + ~ + - c~]( ~ ~ TK) ~ [VK
d ~C 2 [ 1 -~+ ~, (1 + ~)]
Setting the derivative equal to zero and solving yields:
.vV~ ~ VK 1 - ~ + ~ Eq. 5A
Claims (19)
1. A temperature-compensated solid-state voltage reference comprising:
first voltage source means producing a first voltage following a voltage-vs-temperature characteristic curve with a first slope, second voltage source means producing a second voltage and combined with said first voltage to produce a com-posite reference output voltage responsive to said first and second voltages, said second voltage following a voltage-vs-temperature characteristic curve with a second slope, control circuit means operable with said second voltage source means and including means controlling two inde-pendent aspects of said characteristic curve of said second voltage source means in accordance with pre-selected parameters of the control circuit means elements, one of said aspects being the slope of the curve, said control circuit means further including adjustable means to vary said second voltage to alter corres-pondingly said composite reference voltage;
said control circuit means including means under the control of said adjustable means to vary said second slope as said second voltage is changed to provide, in conjunction with said pre-selected parameters, a predetermined temperature co-efficient for said composite voltage when it has been adjusted to a particular specified value pre-selected from a wide range of possible values,
first voltage source means producing a first voltage following a voltage-vs-temperature characteristic curve with a first slope, second voltage source means producing a second voltage and combined with said first voltage to produce a com-posite reference output voltage responsive to said first and second voltages, said second voltage following a voltage-vs-temperature characteristic curve with a second slope, control circuit means operable with said second voltage source means and including means controlling two inde-pendent aspects of said characteristic curve of said second voltage source means in accordance with pre-selected parameters of the control circuit means elements, one of said aspects being the slope of the curve, said control circuit means further including adjustable means to vary said second voltage to alter corres-pondingly said composite reference voltage;
said control circuit means including means under the control of said adjustable means to vary said second slope as said second voltage is changed to provide, in conjunction with said pre-selected parameters, a predetermined temperature co-efficient for said composite voltage when it has been adjusted to a particular specified value pre-selected from a wide range of possible values,
2. Apparatus as claimed in claim 1, wherein said control circuit means is operative to provide an effective zero temperature coefficient for said composite voltage when it reaches said specified value.
3. Apparatus as claimed in claim 2, wherein said control circuit means is operable to produce an effective in-verse match between said two slopes when said composite voltage reaches said specified value, to achieve a zero temperature co-efficient at that voltage.
4. Apparatus as claimed in claim 1, wherein said first voltage source means comprises a Zener diode.
5. Apparatus as claimed in claim 4, wherein said second voltage source means comprises means for producing a compensating voltage which is a function of the base-to-emitter voltage of a semiconductor junction.
6. Apparatus as claimed in claim 4, including an operational amplifier having a pair of input terminals;
means connecting said Zener diode in a negative feedback path between the output of said amplifier and one of its input terminals, said control circuit means comprising first means connected between said output line and the other amplifier input terminal, and second means connected between said other terminal and a common line, the amplifier output voltage being a composite including the Zener diode voltage and the voltage applied to said second amplifier input terminal.
means connecting said Zener diode in a negative feedback path between the output of said amplifier and one of its input terminals, said control circuit means comprising first means connected between said output line and the other amplifier input terminal, and second means connected between said other terminal and a common line, the amplifier output voltage being a composite including the Zener diode voltage and the voltage applied to said second amplifier input terminal.
7. Apparatus as claimed in claim 6, wherein said second means comprises a transistor in series with a resistor.
8. Apparatus as claimed in claim 7, wherein said first means comprises another transistor in series with a resistor.
9. Apparatus as claimed in claim 8, including a voltage divider having a first tap point connected to the base of said first transistor and a second tap point connected to the base of said second transistor;
said adjustment means comprising one of said resistors.
said adjustment means comprising one of said resistors.
10. In the art of temperature-compensating the voltage of a solid-state voltage source by connecting thereto second voltage source means producing a second voltage so as to develop a composite reference voltage corresponding to the sum-mation of said first and second voltages, and wherein the volt-age-vs-temperature characteristic curves of said two voltages have opposite signs so that the temperature effects tend to cancel in said reference voltage, the improved method for providing temperature compensation for a reference voltage of any specified value within a wide range of possible values, comprising the steps of:
connecting to said second voltage source means a control circuit serving to control two independent aspects of said characteristics curve of said second voltage source means in accordance with preselected parameters of said control cir-cuit, with one of said aspects being the slope of the curve;
adjusting a circuit element of said control cir-cuit so as to vary said second voltage and thereby alter said reference voltage to said specified value, and controlling through said adjustment of said cir-cuit element the slope aspect of the characteristic voltage-vs-temperature curve of said second voltage to produce, to-gether with the pre-selected control of the other aspect of that curve, a predetermined relationship between the effects on said composite reference voltage of the temperature character-istics of said first and second voltages so as to provide a predetermined temperature coefficient for said reference voltage when it has been adjusted to said specified value.
connecting to said second voltage source means a control circuit serving to control two independent aspects of said characteristics curve of said second voltage source means in accordance with preselected parameters of said control cir-cuit, with one of said aspects being the slope of the curve;
adjusting a circuit element of said control cir-cuit so as to vary said second voltage and thereby alter said reference voltage to said specified value, and controlling through said adjustment of said cir-cuit element the slope aspect of the characteristic voltage-vs-temperature curve of said second voltage to produce, to-gether with the pre-selected control of the other aspect of that curve, a predetermined relationship between the effects on said composite reference voltage of the temperature character-istics of said first and second voltages so as to provide a predetermined temperature coefficient for said reference voltage when it has been adjusted to said specified value.
11. The method of claim 10, wherein said pre-selected temperature coefficient is zero.
12. The method of claim 10, wherein said first source comprises a Zener diode and said second source comprises the base-to-emitter junction of a transistor in series with an emitter resistor;
said circuit element adjustment being effected by trimming said emitter resistor,
said circuit element adjustment being effected by trimming said emitter resistor,
13. The method of claim 10, wherein said two voltages are combined by connecting said Zener diode in a negative feed-back path between the output and one input terminal of an oper-ational amplifier, and connecting said second voltage source means to the other input terminal.
14, In a solid-state voltage reference device includ-ing as its basic voltage source one of a first class of elements producing a voltage which follows a voltage-vs-temperature char-acteristic curve with a slope differing between units of the class within a wide range, and wherein the extrapolated tempera-ture characteristic curves of all of the units of such class pass through a common region about the graphical intersection of a particular voltage and a corresponding temperature-compensating means coupled to said source to provide temperature compensation for said device comprising a second source producing a second voltage, means connecting said second voltage effectively in series with said first voltage to develop a composite refer-ence output voltage;
said second source being one of a second class of elements having an output voltage which follows a voltage-vs-temperature characteristic curve the slope of which has a sign opposite to that of the slope of the characteristic curve of said first source and wherein the extrapolated curves of the elements of the class can be controlled to pass through a common region about the graphical intersection of some voltage and temperature;
said compensating means including circuit means coupled to said second source to effect optimal temperature compensation when adjusted to produce a pre-specified compos-ite reference voltage selected from a wide range of possible said circuit means including means to control the temperature response characteristics of said second source so that an extrapolation of the characteristic curve thereof passes through a second common region located at the graphical intersection of a pre-selected temperature and a second voltage;
said circuit means further including adjustable means to alter the slope of said characteristic curve of said second source without altering the passing thereof through said second common region, so as to provide a predetermined relation-ship with respect to the slope of said first source, whereby when said adjustable means has been set to produce a final out-put voltage of said pre-specified value, the voltage reference device will be optimally temperature-compensated.
said second source being one of a second class of elements having an output voltage which follows a voltage-vs-temperature characteristic curve the slope of which has a sign opposite to that of the slope of the characteristic curve of said first source and wherein the extrapolated curves of the elements of the class can be controlled to pass through a common region about the graphical intersection of some voltage and temperature;
said compensating means including circuit means coupled to said second source to effect optimal temperature compensation when adjusted to produce a pre-specified compos-ite reference voltage selected from a wide range of possible said circuit means including means to control the temperature response characteristics of said second source so that an extrapolation of the characteristic curve thereof passes through a second common region located at the graphical intersection of a pre-selected temperature and a second voltage;
said circuit means further including adjustable means to alter the slope of said characteristic curve of said second source without altering the passing thereof through said second common region, so as to provide a predetermined relation-ship with respect to the slope of said first source, whereby when said adjustable means has been set to produce a final out-put voltage of said pre-specified value, the voltage reference device will be optimally temperature-compensated.
15. Apparatus as claimed in claim 14, wherein said basic voltage source comprises a Zener diode;
said compensating means including a transistor with a forward-biased junction and arranged to produce said second voltage responsive to changes in the transistor base-to-emitter voltage;
said adjustable means including means to adjust the current through said transistor.
said compensating means including a transistor with a forward-biased junction and arranged to produce said second voltage responsive to changes in the transistor base-to-emitter voltage;
said adjustable means including means to adjust the current through said transistor.
16, Apparatus as claimed in claim 14, comprising a bridge circuit with two arms each having at least two series-connected circuit elements;
one of said arms including a Zener diode in series with a resistor;
the other of said arms including two series-connected transistors each with an emitter resistor, an operational amplifier;
means connecting a point between said transistors to one of said terminals, means connecting the other terminal between the zenerZener diode and its series resistor, and feedback means connecting the amplifier output o said Zener diode.
one of said arms including a Zener diode in series with a resistor;
the other of said arms including two series-connected transistors each with an emitter resistor, an operational amplifier;
means connecting a point between said transistors to one of said terminals, means connecting the other terminal between the zenerZener diode and its series resistor, and feedback means connecting the amplifier output o said Zener diode.
17. In the art of temperature compensating solid-state voltage sources of the type producing output voltages which follow voltage-vs-temperature characteristic curves the slopes of which vary between individual voltage source units within a wide range of values all having the same sign, and wherein the characteristic curves of all such units pass through a common region located at the graphical intersection of a particular voltage and a corresponding temperature;
the improved method comprising the steps of:
connecting to such voltage source a second voltage source producing a compensating voltage which is effect-ively combined with said output voltage to produce a reference voltage;
said second source voltage following a voltage-vs-temperature characteristic curve the slope of which is opposite in sign to that of the first voltage source;
coupling to said second voltage source a control circuit means including an adjustable element for altering the magnitude of said compensating voltage, thereby to change said reference voltage correspondingly, and further including means for controlling the slope of the characteristic curve and for predeterminedly setting the curve pivot location about which the slope of the curve can be varied;
adjusting said control circuit means element to produce a reference voltage of a pre-specified value selected from a wide range of possible values; and effecting through adjustment of said control circuit means element a simultaneous alteration of the slope of the voltage-vs-temperature characteristic curve of said second voltage source to produce a slope thereof which is inversely related to that of the first voltage source when said reference voltage has been adjusted to said pre-specified value.
the improved method comprising the steps of:
connecting to such voltage source a second voltage source producing a compensating voltage which is effect-ively combined with said output voltage to produce a reference voltage;
said second source voltage following a voltage-vs-temperature characteristic curve the slope of which is opposite in sign to that of the first voltage source;
coupling to said second voltage source a control circuit means including an adjustable element for altering the magnitude of said compensating voltage, thereby to change said reference voltage correspondingly, and further including means for controlling the slope of the characteristic curve and for predeterminedly setting the curve pivot location about which the slope of the curve can be varied;
adjusting said control circuit means element to produce a reference voltage of a pre-specified value selected from a wide range of possible values; and effecting through adjustment of said control circuit means element a simultaneous alteration of the slope of the voltage-vs-temperature characteristic curve of said second voltage source to produce a slope thereof which is inversely related to that of the first voltage source when said reference voltage has been adjusted to said pre-specified value.
18. In a solid-state voltage reference device including as its basic voltage source one of a first class of elements producing a voltage which follows a voltage-vs-temper-ature characteristic curve with a slope differing between units of the class within a wide range, and wherein the extrapolated temperature characteristic curves of all of the units of such class pass through a common region about the graphical inter-section of a particular voltage and a corresponding tempera-ture;
compensating means coupled to said source to provide temperature compensation for said device comprising a second source producing a second voltage;
means connecting said second voltage effectively in series with said first voltage to develop a composite refer-ence output voltage;
said second source being one of a second class of elements having an output voltage which follows a voltage-vs-temperature characteristic curve the slope of which has a sign opposite to that of the slope of the characteristic curve of said first source and wherein the extrapolated curves of the elements of said second class can be controlled to pass through a common region about the graphical intersection of some voltage and temperature;
said compensating means including circuit means coupled to said second source to effect optimal temperature compensation when adjusted to produce a pre-specified composite reference voltage selected from a wide range of possible refer-ence voltages;
said circuit means including means to control the temperature response characteristics of said second source so that an extrapolation of the characteristic curve thereof passes through a second common region located at the graphical intersection of said corresponding temperature and a second voltage which when added to said particular voltage will pro-duce said pre-specified composite reference voltage;
said circuit means further including adjustable means to alter the slope of said characteristic curve of said second source about said second common region as a pivot point to prevent altering the passing of said curve through said second common region, said slope being alterable so as to match inversely the slope of said first source and produce a substan-tially zero temperature coefficient for the composite voltage, whereby when said adjustable means has been set to produce a final output voltage of said prespecified value, at any temper-ature, the voltage reference device will be temperature-compen-sated to provide a zero temperature coefficient.
compensating means coupled to said source to provide temperature compensation for said device comprising a second source producing a second voltage;
means connecting said second voltage effectively in series with said first voltage to develop a composite refer-ence output voltage;
said second source being one of a second class of elements having an output voltage which follows a voltage-vs-temperature characteristic curve the slope of which has a sign opposite to that of the slope of the characteristic curve of said first source and wherein the extrapolated curves of the elements of said second class can be controlled to pass through a common region about the graphical intersection of some voltage and temperature;
said compensating means including circuit means coupled to said second source to effect optimal temperature compensation when adjusted to produce a pre-specified composite reference voltage selected from a wide range of possible refer-ence voltages;
said circuit means including means to control the temperature response characteristics of said second source so that an extrapolation of the characteristic curve thereof passes through a second common region located at the graphical intersection of said corresponding temperature and a second voltage which when added to said particular voltage will pro-duce said pre-specified composite reference voltage;
said circuit means further including adjustable means to alter the slope of said characteristic curve of said second source about said second common region as a pivot point to prevent altering the passing of said curve through said second common region, said slope being alterable so as to match inversely the slope of said first source and produce a substan-tially zero temperature coefficient for the composite voltage, whereby when said adjustable means has been set to produce a final output voltage of said prespecified value, at any temper-ature, the voltage reference device will be temperature-compen-sated to provide a zero temperature coefficient.
19 In the art of temperature compensating solid-state voltage sources of the type producing output voltages which follow voltage-vs-temperature characteristic curves the slopes of which vary between individual voltage source units within a wide range of values all having the same sign, and wherein the characteristic curves of all such units pass through a common region located at the graphical intersection of a par-ticular voltage and a corresponding temperature;
the improved method comprising the steps of:
connecting to such voltage source a second voltage source producing a compensating voltage which is effec-tively combined with said output voltage to produce a reference voltage;
said second source being of the type having voltage-vs-temperature characteristic curves the slopes of which are opposite in sign to that of the first voltage source and are adjustable about a curve pivot point;
coupling to said second voltage source a control.
circuit means predeterminedly setting the curve pivot location to fall on said corresponding temperature;
adjusting an element of said control circuit means to produce a reference voltage of a pre-specified value selected from a wide range of possible values, and effecting through adjustment of said control cir-cuit means element a simultaneous alteration of the slope of the voltage-vs-temperature characteristic curve of said second voltage source about said curve pivot location to produce a slope thereof which is inversely matched to that of the first voltage source when said reference voltage has been adjusted to said pre-specified value.
the improved method comprising the steps of:
connecting to such voltage source a second voltage source producing a compensating voltage which is effec-tively combined with said output voltage to produce a reference voltage;
said second source being of the type having voltage-vs-temperature characteristic curves the slopes of which are opposite in sign to that of the first voltage source and are adjustable about a curve pivot point;
coupling to said second voltage source a control.
circuit means predeterminedly setting the curve pivot location to fall on said corresponding temperature;
adjusting an element of said control circuit means to produce a reference voltage of a pre-specified value selected from a wide range of possible values, and effecting through adjustment of said control cir-cuit means element a simultaneous alteration of the slope of the voltage-vs-temperature characteristic curve of said second voltage source about said curve pivot location to produce a slope thereof which is inversely matched to that of the first voltage source when said reference voltage has been adjusted to said pre-specified value.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94632678A | 1978-09-27 | 1978-09-27 | |
| US946,326 | 1978-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1141820A true CA1141820A (en) | 1983-02-22 |
Family
ID=25484320
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000336481A Expired CA1141820A (en) | 1978-09-27 | 1979-09-27 | Temperature compensated ic voltage reference |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5556212A (en) |
| CA (1) | CA1141820A (en) |
| DE (1) | DE2938849C2 (en) |
| FR (1) | FR2437656A1 (en) |
| GB (1) | GB2032659B (en) |
| NL (1) | NL7907161A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4315209A (en) * | 1980-07-14 | 1982-02-09 | Raytheon Company | Temperature compensated voltage reference circuit |
| US4677369A (en) * | 1985-09-19 | 1987-06-30 | Precision Monolithics, Inc. | CMOS temperature insensitive voltage reference |
| GB2198559B (en) * | 1986-12-09 | 1990-09-12 | Stc Plc | Voltage reference circuit |
| FR2680587B1 (en) * | 1991-08-23 | 1993-10-15 | Thomson Csf | CONTROL AND REGULATION METHOD AND DEVICE. |
| DE4137730C2 (en) * | 1991-11-15 | 1993-10-21 | Texas Instruments Deutschland | Circuit arrangement integrated in a semiconductor circuit |
| DE4223295C1 (en) * | 1992-07-15 | 1994-01-13 | Siemens Ag | Reference voltage raising circuit - uses operational amplifier controlling pair of current sources to provide temp.-independent output reference potential |
| DE19621749C2 (en) * | 1996-05-30 | 1998-07-16 | Siemens Ag | Circuit arrangement for generating a resistance behavior with adjustable positive temperature coefficient and use of this circuit arrangement |
| US7543253B2 (en) * | 2003-10-07 | 2009-06-02 | Analog Devices, Inc. | Method and apparatus for compensating for temperature drift in semiconductor processes and circuitry |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2314423C3 (en) * | 1973-03-23 | 1981-08-27 | Robert Bosch Gmbh, 7000 Stuttgart | Method for producing a reference DC voltage source |
| US3826969A (en) * | 1973-04-02 | 1974-07-30 | Gen Electric | Highly stable precision voltage source |
| US3947704A (en) * | 1974-12-16 | 1976-03-30 | Signetics | Low resistance microcurrent regulated current source |
| GB1549689A (en) * | 1975-07-28 | 1979-08-08 | Nippon Kogaku Kk | Voltage generating circuit |
-
1979
- 1979-09-26 NL NL7907161A patent/NL7907161A/en not_active Application Discontinuation
- 1979-09-26 DE DE19792938849 patent/DE2938849C2/en not_active Expired - Lifetime
- 1979-09-27 JP JP12465879A patent/JPS5556212A/en active Granted
- 1979-09-27 GB GB7933524A patent/GB2032659B/en not_active Expired
- 1979-09-27 FR FR7924041A patent/FR2437656A1/en active Granted
- 1979-09-27 CA CA000336481A patent/CA1141820A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2938849A1 (en) | 1980-04-17 |
| NL7907161A (en) | 1980-03-31 |
| JPS5556212A (en) | 1980-04-24 |
| GB2032659B (en) | 1983-05-18 |
| JPH0135364B2 (en) | 1989-07-25 |
| FR2437656B1 (en) | 1983-08-05 |
| FR2437656A1 (en) | 1980-04-25 |
| DE2938849C2 (en) | 1993-11-25 |
| GB2032659A (en) | 1980-05-08 |
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