US20020047696A1 - Generation of a voltage proportional to temperature with accurate gain control - Google Patents
Generation of a voltage proportional to temperature with accurate gain control Download PDFInfo
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- US20020047696A1 US20020047696A1 US09/854,139 US85413901A US2002047696A1 US 20020047696 A1 US20020047696 A1 US 20020047696A1 US 85413901 A US85413901 A US 85413901A US 2002047696 A1 US2002047696 A1 US 2002047696A1
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- 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
- G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
- G05F3/30—Regulators using the difference between the base-emitter voltages of two bipolar transistors operating at different current densities
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S323/00—Electricity: power supply or regulation systems
- Y10S323/907—Temperature compensation of semiconductor
Definitions
- the present invention relates to a circuit for generating an output voltage which is proportional to temperature with a required gradient.
- Such circuits exist which rely on the principle that the difference in the base emitter voltage of two bipolar transistors with differing areas, if appropriately connected, can result in a current which has a positive temperature coefficient, that is a current which varies linearly with temperature such that as the temperature increases the current increases.
- This current referred to herein as Iptat
- Vptat can be used to generate a voltage proportional to absolute temperature, Vptat, when supplied across a resistor.
- the present invention provides a circuit for generating an output voltage proportional to temperature with a required gradient, the circuit comprising: a first stage arranged to generate a first voltage which is proportional to temperature with a predetermined gradient, the first stage comprising: first and second bipolar transistors with different emitter areas having their emitters connected together and their bases connected across a bridge resistive element, wherein the collectors of the transistors are connected to an internal supply line via respective matched resistive elements such that the voltage across the bridge resistive element is proportional to temperature; a differential amplifier having its inputs connected respectively to said collectors, and its output connected to stabilisation circuitry connected between first and second power supply rails and an internal supply line which cooperates with the differential amplifier to maintain a stable voltage on the internal supply line despite variations between the first and second power supply rails; and a second stage which comprises a gain circuit connected to receive the first voltage for altering the predetermined gradient to match the required gradient, the gain circuit having as its voltage supply said stable voltage on the internal supply line.
- FIG. 1 represents circuitry of the first stage
- FIG. 2 represents construction of a resistive chain
- FIG. 3 represents circuitry of the second stage
- FIG. 4 is a graph illustrating the variation of temperature with voltage for circuits with and without use of the present invention.
- FIG. 5 represents circuitry of another form of second stage.
- the present invention is concerned with a circuit for the generation of a voltage proportional to absolute temperature (Vptat).
- the circuit has two stages which are referred to herein as the first stage and the second stage.
- a “raw” voltage Vptat is generated, and in the second stage a calibrated voltage for measurement purposes is generated from the “raw” voltage.
- FIG. 1 illustrates one embodiment of the first stage.
- the core of the voltage generation circuit comprises two bipolar transistors Q 0 ,Q 1 which have different emitter areas.
- K Boltzmanns constant
- T temperature
- q the electron charge
- Ic 0 the collector current through the transistor Q 0
- Ic 1 the collector current through the transistor Q 1
- Is 0 the saturation current of the transistor Q 0
- Is 1 the saturation current of the transistor Q 1 .
- the saturation current is dependent on the emitter area, such that the ratio Is 0 divided by Is 1 is equal to the ratio of the emitter area of the transistor Q 0 to the emitter area of the transistor Q 1 . In the described embodiment, that ratio is 8. Also, the circuit illustrated in FIG.
- This current Iptat is passed through a resistive chain Rx to generate the temperature dependent voltage Vptat at a node N 1 .
- a resistor R 3 is connected between R 2 and ground.
- the collector currents Ic 1 , Ic 0 are forced to be equal by matching resistors R 0 , R 1 in the collector paths as closely as possible. However, it is also important to maintain the collector voltages of the transistors Q 0 ,Q 1 as close to one another as possible to match the collector currents. This is achieved by connecting the two inputs of a differential amplifier AMP 1 to the respective collector paths. The amplifier AMP 1 is designed to hold its inputs very close to one another. In the described embodiments, the input voltage Vio of the amplifier AMP 1 is less then 1 mV so that the matching of the collector voltages of the transistors Q 0 ,Q 1 is very good. This improves the linearity of operation of the circuit.
- Vddint denotes an internal line voltage which is set and stabilised as described in the following.
- a transistor Q 4 has its emitter connected to Vddlnt and its collector connected to the amplifier AMP 1 to act as a current source for the amplifier AMP 1 . It is connected in a mirror configuration with a bipolar transistor Q 6 which has its base connected to its collector. The transistor Q 6 is connected in series to an opposite polarity transistor Q 8 , also having its base connected to its collector.
- the bipolar transistors Q 8 and Q 6 assist in setting the value of the internal line voltage V ddint at a stable voltage to a level given by, to a first approximation,
- V ddint is a reasonably stable voltage because the decrease across Q 6 and Q 8 with rising temperature is compensated by the increase in Vptat.
- the amplifier AMP 1 has a secondary purpose, provided at no extra overhead, to the main purpose of equalising the collector voltages Q 0 and Q 1 , discussed above.
- the secondary use is for stabilising the line voltage V ddint .
- V ddint is disturbed by fluctuating voltage or current due to excessive current taken from the second stage (discussed later) or noise or power supply coupling onto it.
- the voltage on line V ddint will go up or down slightly. If V ddint goes higher, then the potential at resistor R 2 and R 3 will rise. Icl will increase slightly more than IcO and the difference across AMP 1 increases.
- AMP 1 is a transconductance amplifier and as the Vic increases more current is drawn through Q 2 , i.e.
- the base of a transistor Q 9 connected between the transistor Q 2 and V supply is connected to receive a start-up signal from a start-up circuit (not shown).
- the transistor Q 9 acts as a current source for the transistor Q 2 .
- An additional bipolar transistor Q 5 is connected between the common emitter connection of the voltage generating transistors Q 0 ,Q 1 and has its base connected to receive a start-up signal from the start-up circuit. It functions as the “tail” of the Vptat transistors Q 0 ,Q 1 .
- the temperature dependent voltage Vptat generated by the first stage illustrated in FIG. 1 has a good linear variation at the calculated slope ⁇ 4.53 mV/° C.
- the internal line voltage V ddint limits the swing in the upper direction, and also Vptat cannot go down to zero.
- the resistive chain Rx constitutes a sequence of resistors connected in series as illustrated for example in FIG. 2.
- the slope of the temperature dependent voltage is dependent on the resistive value in the resistive chain Rx and thus can be altered by tapping off the voltage at different points P 1 ,P 2 ,P 3 in FIG. 2.
- FIG. 3 illustrates the second stage of the circuit which functions as a gain stage.
- the circuit comprises a differential amplifier AMP 2 having a first input 10 connected to receive the temperature dependent voltage Vptat at node N 1 from the first stage and a second input 12 serving as a feedback input.
- the output of the differential amplifier AMP 2 is connected to a Darlington pair of transistors Q 10 , Q 11 .
- Darlington pair supplies an output voltage Vout at node 14 .
- the amplifier AMP 2 and the first Darlington transistor Q 10 are connected to the stable voltage line V ddint supplied by the first stage.
- the second Darlington transistor is connected to V supply .
- the output voltage Vout is a voltage which is proportional to temperature with a required gradient and which can move negative with negative temperatures.
- the adjustment of the slope of the temperature versus voltage curve is achieved in the second stage by a feedback loop for the differential amplifier AMP 2 .
- the feedback loop comprises a gain resistor R 4 connected between the output terminal 14 at which the output voltage Vout is taken and the base of a feedback transistor Q 12 .
- the collector of the feedback transistor Q 12 is connected to ground and its emitter is connected into a resistive chain Ry, the value of which can be altered and which is constructed similarly to the resistive chain Rx in FIG. 2.
- a resistor R 5 is connected between the resistor R 4 and ground.
- the gain of the feedback loop including differential amplifier AMP 2 can be adjusted by altering the ratio: R4 + R5 R5 ( 6 )
- the voltage Vptat at the node N 1 cannot move into negative values even when the temperature moves negative.
- the second stage of the circuit accomplishes this by providing an offset circuit 22 connected to the input terminal 12 of the differential amplifier AMP 2 .
- the offset circuit 22 comprises the resistor chain Ry and the transistor Q 12 . Together these components provide a relatively stable bandgap voltage of about 1.25 V.
- the resistive chain Ry receives the current Iptat mirrored from the first stage via two bipolar transistors Q 13 , Q 14 of opposite types which are connected in opposition and which cooperate with the transistors Q 6 and Q 8 of the first stage to act as a current mirror to mirror the temperature dependent current lptat.
- Vbe(Q 12 ) decreases.
- This offset circuit 22 introduces a fixed voltage offset at the input terminal 12 , thus shifting the line of voltage with respect to temperature. This shift can be seen in FIG. 4, where the curve of the output voltage Vout at node 14 can be seen to pass through zero and move negative at negative temperatures.
- the “bridge” network in the first stage performs a number of different functions, as follows. Firstly, it provides a temperature related voltage Vptat at the node N 1 . Secondly, it assists in providing a relatively fixed internal supply voltage V ddint even in the face of external supply variations, thus giving good line regulation for the gain circuit of the second stage. Thirdly, it provides in conjunction with the current mirror transistors Q 4 ,Q 6 current biasing for the amplifier AMP 1 of the first stage. Fourthly, it provides, through the mirroring of transistors Q 6 ,Q 13 current biasing for the resistive chain Ry in the offset circuit 22 of the second stage.
- Table 1 illustrates the operating parameters of one particular embodiment of the circuit. To achieve the operating parameters given in Table 1, adjustment can be made using the resistive chain Rx implemented in the manner illustrated in FIG. 2 to adjust the slope of Vptat in the first stage.
- the slope may be adjusted in the second stage by altering the gain resistors R 4 ,R 5 .
- TABLE 1 Parameter Conditions Min Typ Max Units Accuracy T 25 C. +/ ⁇ 2 deg C. ⁇ 30 ⁇ T ⁇ 130 C. Sensor Gain ⁇ 30 ⁇ T ⁇ 130 C. 10 mv/deg C.
- Load Regulation 0 ⁇ Iout ⁇ 1 mA 15 mV/mA Line Regulation 4.0 ⁇ VCC ⁇ 11 V +/ ⁇ 0.5 mV/V Quiescent current 4.0 ⁇ VCC ⁇ 11 V 80 uA T 25 C.
- FIG. 5 represents an alternative second stage which includes a differential amplifier AMP 2 in a feedback loop as in the circuit of FIG. 3.
- the second stage illustrated in FIG. 5 differs from that in FIG. 3 in that there is no offset circuit. Instead, the transistor Q 12 is connected via a current mirror CM 1 to the supply line V Supply .
- This second stage allows the gradient of the temperature dependent voltage at node N 1 to be altered but does not allow it to move negative with negative temperatures.
- CM 2 denotes a second current mirror in the circuit of FIG. 5.
- the second stage of FIG. 5 nevertheless still makes use of the stable internal voltage supply line V ddint to supply the differential amplifier AMP 2 .
- Table II illustrates the operating parameters of an embodiment of the invention using the stage of FIG. 5.
- FIG. 5 represents an alternative second stage which includes a differential amplifier AMP 2 in a feedback loop as in the circuit of FIG. 3.
- the second stage illustrated in FIG. 5 differs from that in FIG. 3 in that there is no offset circuit. Instead, the transistor Q 12 is connected via a current mirror CM 1 to the supply line V supply .
- This second stage allows the gradient of the temperature dependent voltage at node N 1 to be altered but does not allow it to move negative with negative temperatures.
- CM 2 denotes a second current mirror in the circuit of FIG. 5.
- the second stage of FIG. 5 nevertheless still makes use of the stable internal voltage supply line V ddint to supply the differential amplifier AMP 2 .
- Table II illustrates the operating parameters of an embodiment of the invention using the stage of FIG. 5.
Abstract
A circuit for generating an output voltage which is proportional to temperature with a required gradient is disclosed. The circuit relies on the principle that the difference in the base emitter voltage of two bipolar transistors with differing areas, if appropriately connected, can result in a current which has a positive temperature coefficient, that is a current which varies linearly with temperature such that as the temperature increases the current increases. It is important to maintain a stable internal line voltage in the face of significant variations in a supply voltage to the circuit. This is achieved herein by providing control elements appropriately connected to a differential amplifier. The stable internal supply voltage can be used to power a subsequent stage of the circuit for fine control of the gradient of the voltage proportional to temperature.
Description
- The present invention relates to a circuit for generating an output voltage which is proportional to temperature with a required gradient.
- Such circuits exist which rely on the principle that the difference in the base emitter voltage of two bipolar transistors with differing areas, if appropriately connected, can result in a current which has a positive temperature coefficient, that is a current which varies linearly with temperature such that as the temperature increases the current increases. This current, referred to herein as Iptat, can be used to generate a voltage proportional to absolute temperature, Vptat, when supplied across a resistor.
- One such practical difficulty is the need to accurately control the required gradient of variation of the voltage with respect to temperature. In a circuit of the type mentioned above, this can be done by controlling the value of resistance through which the current proportional to absolute temperature Iptat is supplied. However, this may not give adequate control of the gradient and it is desirable therefore to incorporate a second stage which allows the finer adjustment of the gradient to be made. It is an aim of the present invention to incorporate such a second stage in an environment with good line regulation for the first and second stages.
- The present invention provides a circuit for generating an output voltage proportional to temperature with a required gradient, the circuit comprising: a first stage arranged to generate a first voltage which is proportional to temperature with a predetermined gradient, the first stage comprising: first and second bipolar transistors with different emitter areas having their emitters connected together and their bases connected across a bridge resistive element, wherein the collectors of the transistors are connected to an internal supply line via respective matched resistive elements such that the voltage across the bridge resistive element is proportional to temperature; a differential amplifier having its inputs connected respectively to said collectors, and its output connected to stabilisation circuitry connected between first and second power supply rails and an internal supply line which cooperates with the differential amplifier to maintain a stable voltage on the internal supply line despite variations between the first and second power supply rails; and a second stage which comprises a gain circuit connected to receive the first voltage for altering the predetermined gradient to match the required gradient, the gain circuit having as its voltage supply said stable voltage on the internal supply line.
- For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which:
- FIG. 1 represents circuitry of the first stage;
- FIG. 2 represents construction of a resistive chain;
- FIG. 3 represents circuitry of the second stage;
- FIG. 4 is a graph illustrating the variation of temperature with voltage for circuits with and without use of the present invention; and
- FIG. 5 represents circuitry of another form of second stage.
- The present invention is concerned with a circuit for the generation of a voltage proportional to absolute temperature (Vptat). The circuit has two stages which are referred to herein as the first stage and the second stage. In the first stage, a “raw” voltage Vptat is generated, and in the second stage a calibrated voltage for measurement purposes is generated from the “raw” voltage.
-
-
- The difference ΔVbe is dropped across a bridge resistor R2 to generate a current proportional to absolute temperature Iptat, where:
- Iptat=ΔVbe/R2 (2)
- This current Iptat is passed through a resistive chain Rx to generate the temperature dependent voltage Vptat at a node N1. A resistor R3 is connected between R2 and ground.
-
-
- With the values indicated above R2=18K, R3=36K, Rx=85K, the variation of voltage with temperature is 4.53 mV/° C.
- Before discussing how Vptat is modified in the second stage, other attributes of the circuit of the first stage will be discussed.
- The collector currents Ic1, Ic0 are forced to be equal by matching resistors R0, R1 in the collector paths as closely as possible. However, it is also important to maintain the collector voltages of the transistors Q0,Q1 as close to one another as possible to match the collector currents. This is achieved by connecting the two inputs of a differential amplifier AMP1 to the respective collector paths. The amplifier AMP1 is designed to hold its inputs very close to one another. In the described embodiments, the input voltage Vio of the amplifier AMP1 is less then 1 mV so that the matching of the collector voltages of the transistors Q0,Q1 is very good. This improves the linearity of operation of the circuit.
- Vddint denotes an internal line voltage which is set and stabilised as described in the following. A transistor Q4 has its emitter connected to Vddlnt and its collector connected to the amplifier AMP1 to act as a current source for the amplifier AMP1. It is connected in a mirror configuration with a bipolar transistor Q6 which has its base connected to its collector. The transistor Q6 is connected in series to an opposite polarity transistor Q8, also having its base connected to its collector.
- The bipolar transistors Q8 and Q6 assist in setting the value of the internal line voltage Vddint at a stable voltage to a level given by, to a first approximation,
- Vddint−Iptat(R3+R2+Rx+Rz)+Vbe(Q6)+Vbe(Q8) (5)
- According to the principal on which bandgap voltage regulators are based, as Vptat increases with temperature, the Vbe of transistors Q6 and Q8 decrease due to the temperature dependence of Vbe in a bipolar transistor. Thus, Vddint is a reasonably stable voltage because the decrease across Q6 and Q8 with rising temperature is compensated by the increase in Vptat.
- The amplifier AMP1 has a secondary purpose, provided at no extra overhead, to the main purpose of equalising the collector voltages Q0 and Q1, discussed above. The secondary use is for stabilising the line voltage Vddint. Imagine if Vddint is disturbed by fluctuating voltage or current due to excessive current taken from the second stage (discussed later) or noise or power supply coupling onto it. The voltage on line Vddint will go up or down slightly. If Vddint goes higher, then the potential at resistor R2 and R3 will rise. Icl will increase slightly more than IcO and the difference across AMP1 increases. AMP1 is a transconductance amplifier and as the Vic increases more current is drawn through Q2, i.e. Ic2 increases. Q3 is starved of base current and switches off allowing Vddint to recover by current discharge through the resistor bridge. The opposite occurs when Vddint goes low in which case AMP1 supplies less current to the base of Q2 therefore the current Ic2 decreases and mor ecurrent from Q9 can go to the base of Q3 allowing more drive current lc3 to supply Vddint. In effect there is some stabilisation.
- The base of a transistor Q9 connected between the transistor Q2 and Vsupply is connected to receive a start-up signal from a start-up circuit (not shown). The transistor Q9 acts as a current source for the transistor Q2. An additional bipolar transistor Q5 is connected between the common emitter connection of the voltage generating transistors Q0,Q1 and has its base connected to receive a start-up signal from the start-up circuit. It functions as the “tail” of the Vptat transistors Q0,Q1.
- The temperature dependent voltage Vptat generated by the first stage illustrated in FIG. 1 has a good linear variation at the calculated slope≈4.53 mV/° C. However, the internal line voltage Vddint limits the swing in the upper direction, and also Vptat cannot go down to zero.
- It will be appreciated that the resistive chain Rx constitutes a sequence of resistors connected in series as illustrated for example in FIG. 2. The slope of the temperature dependent voltage is dependent on the resistive value in the resistive chain Rx and thus can be altered by tapping off the voltage at different points P1,P2,P3 in FIG. 2.
- FIG. 3 illustrates the second stage of the circuit which functions as a gain stage. The circuit comprises a differential amplifier AMP2 having a
first input 10 connected to receive the temperature dependent voltage Vptat at node N1 from the first stage and asecond input 12 serving as a feedback input. The output of the differential amplifier AMP2 is connected to a Darlington pair of transistors Q10, Q11. The emitter of the second transistor Q11 in the - Darlington pair supplies an output voltage Vout at
node 14. The amplifier AMP2 and the first Darlington transistor Q10 are connected to the stable voltage line Vddint supplied by the first stage. The second Darlington transistor is connected to Vsupply. - The output voltage Vout is a voltage which is proportional to temperature with a required gradient and which can move negative with negative temperatures.
- The adjustment of the slope of the temperature versus voltage curve is achieved in the second stage by a feedback loop for the differential amplifier AMP2. The feedback loop comprises a gain resistor R4 connected between the
output terminal 14 at which the output voltage Vout is taken and the base of a feedback transistor Q12. The collector of the feedback transistor Q12 is connected to ground and its emitter is connected into a resistive chain Ry, the value of which can be altered and which is constructed similarly to the resistive chain Rx in FIG. 2. A resistor R5 is connected between the resistor R4 and ground. The gain of the feedback loop including differential amplifier AMP2 can be adjusted by altering the ratio: - This allows the slope of the incoming temperature dependent voltage Vptat to be adjusted between the gradient produced by the first stage at N1 and the required gradient at the
output terminal 14. In the described example, the slope of the temperature dependent voltage Vptat at N1 with respect to temperature is 4.53 mV/° C. This is altered by the second stage to 10 mV/° C. This is illustrated in FIG. 4 where the crosses denote the relationship of voltage and temperature at N1 and the diamonds denote the relationship of voltage to temperature for the output voltage at theoutput node 14. - As has already been mentioned, the voltage Vptat at the node N1 cannot move into negative values even when the temperature moves negative. The second stage of the circuit accomplishes this by providing an offset
circuit 22 connected to theinput terminal 12 of the differential amplifier AMP2. The offsetcircuit 22 comprises the resistor chain Ry and the transistor Q12. Together these components provide a relatively stable bandgap voltage of about 1.25 V. The resistive chain Ry receives the current Iptat mirrored from the first stage via two bipolar transistors Q13, Q14 of opposite types which are connected in opposition and which cooperate with the transistors Q6 and Q8 of the first stage to act as a current mirror to mirror the temperature dependent current lptat. As lptat increases with temperature, Vbe(Q12) decreases. This offsetcircuit 22 introduces a fixed voltage offset at theinput terminal 12, thus shifting the line of voltage with respect to temperature. This shift can be seen in FIG. 4, where the curve of the output voltage Vout atnode 14 can be seen to pass through zero and move negative at negative temperatures. - From the above description it can be seen that the “bridge” network in the first stage performs a number of different functions, as follows. Firstly, it provides a temperature related voltage Vptat at the node N1. Secondly, it assists in providing a relatively fixed internal supply voltage Vddint even in the face of external supply variations, thus giving good line regulation for the gain circuit of the second stage. Thirdly, it provides in conjunction with the current mirror transistors Q4,Q6 current biasing for the amplifier AMP1 of the first stage. Fourthly, it provides, through the mirroring of transistors Q6,Q13 current biasing for the resistive chain Ry in the offset
circuit 22 of the second stage. - Table 1 illustrates the operating parameters of one particular embodiment of the circuit. To achieve the operating parameters given in Table 1, adjustment can be made using the resistive chain Rx implemented in the manner illustrated in FIG. 2 to adjust the slope of Vptat in the first stage.
- Alternatively, the slope may be adjusted in the second stage by altering the gain resistors R4,R5.
TABLE 1 Parameter Conditions Min Typ Max Units Accuracy T = 25 C. +/−2 deg C. −30 < T < 130 C. Sensor Gain −30 < T < 130 C. 10 mv/deg C. Load Regulation 0 < Iout < 1 mA 15 mV/mA Line Regulation 4.0 < VCC < 11 V +/−0.5 mV/V Quiescent current 4.0 < VCC < 11 V 80 uA T = 25 C. Operating supply range 4 11 V Output voltage offset 0 V - FIG. 5 represents an alternative second stage which includes a differential amplifier AMP2 in a feedback loop as in the circuit of FIG. 3. However, the second stage illustrated in FIG. 5 differs from that in FIG. 3 in that there is no offset circuit. Instead, the transistor Q12 is connected via a current mirror CM1 to the supply line VSupply. This second stage allows the gradient of the temperature dependent voltage at node N1 to be altered but does not allow it to move negative with negative temperatures. CM2 denotes a second current mirror in the circuit of FIG. 5. The second stage of FIG. 5 nevertheless still makes use of the stable internal voltage supply line Vddint to supply the differential amplifier AMP2. Table II illustrates the operating parameters of an embodiment of the invention using the stage of FIG. 5.
TABLE II Parameter Conditions Min Typ Max Units Accuracy −30 < T < 130 C. +/−2 deg C. Sensor Gain −30 < T > 100 C. 10 mv/deg C. Load Regula- 0 < Iout < 1 mA +/−15 mV/mA tion Line Regula- 4.0 < VCC < 10 V +/−0.5 mV/V tion Quiescent 4.0 < VCC < 10 V 80 uA current Operating sup- 4.5 11 V ply range Output voltage 0.81 V offset - For the circuit of FIG. 5, −10° C.=0.71 V, −20° C.=0.61 V, −30° C.=0.51 V, 100° C.=1.81 V.
- FIG. 5 represents an alternative second stage which includes a differential amplifier AMP2 in a feedback loop as in the circuit of FIG. 3. However, the second stage illustrated in FIG. 5 differs from that in FIG. 3 in that there is no offset circuit. Instead, the transistor Q12 is connected via a current mirror CM1 to the supply line Vsupply. This second stage allows the gradient of the temperature dependent voltage at node N1 to be altered but does not allow it to move negative with negative temperatures. CM2 denotes a second current mirror in the circuit of FIG. 5. The second stage of FIG. 5 nevertheless still makes use of the stable internal voltage supply line Vddint to supply the differential amplifier AMP2. Table II illustrates the operating parameters of an embodiment of the invention using the stage of FIG. 5.
TABLE II Parameter Conditions Min Typ Max Units Accuracy −30 < T < 130 C. +/−2 Deg C. Sensor Gain −30 < T > 100 C. 10 mv/deg C. Load Regula- 0 < Iout < 1 mA +/−15 mV/mA tion Line Regula- 4.0 < VCC < 10 V +/−0.5 mV/V tion Quiescent 4.0 < VCC < 10 V 80 uA current Operating sup- 4.5 11 V ply range Output voltage 0.81 V offset - For the circuit of FIG. 5, −10° C.=0.71 V, −20° C.=0.61 V, −30° C.=0.51 V, 100° C.=1.81 V.
Claims (11)
1. A circuit for generating an output voltage proportional to temperature with a required gradient, the circuit comprising:
first and second bipolar transistors with different emitter areas having their emitters connected together and their bases connected across a bridge resistive element, wherein the collectors of the transistors are connected to an internal supply line via respective matched resistive elements such that the voltage across the bridge resistive element is proportional to temperature;
a differential amplifier having its inputs connected respectively to said collectors and its output connected to a control terminal of a first control element having a controllable path connected between a first power supply rail and a control node;
a second control element having a controllable path connected between the control node and a second power supply rail; and
a third control element having a control terminal connected to the control node and a controllable path connected between the second power supply rail and AN internal supply line, whereby the differential amplifier and the first, second and third control elements cooperate to maintain a stable voltage on the internal supply line despite variations between the first and second power supply rails.
2. A circuit according to claim 1 , wherein the current flowing through the bridge resistive element is a temperature dependent current which is also supplied through a first resistive chain to generate at an output node of the circuit a voltage proportional to temperature with a predetermined gradient determined by the first resistive chain.
3. A circuit according to claim 2 , which comprises first and second bipolar transistors of opposite polarity connected in series between the internal supply line and the output node which serve to set the voltage on the internal supply line.
4. A circuit according to claim 3 , wherein the first and second transistors cooperate with a current supply element to generate a supply current for the differential amplifier.
5. A circuit according to any preceding claim, wherein the first, second and third control elements are bipolar transistors with the base constituting the control terminal and the collector emitter path constituting the controllable path.
6. A circuit according to any preceding claim which comprises a second stage which has a second differential amplifier connected to receive the output voltage proportional to temperature and a second input connected to receive a feedback voltage which is derived from an output signal of the differential amplifier whereby the gain of the output voltage can be adjusted.
7. A circuit according to claim 6 , wherein the second differential amplifier is powered by the stable voltage on the internal supply line.
8. A circuit according to claim 2 or 3, wherein the required gradient is programmable through variation of the resistance of the first resistive chain.
9. A circuit according to claim 6 or 7, wherein the feedback voltage in the second stage is derived from the output signal of a differential amplifier via an offset circuit which introduces an offset voltage such that the output signal of a differential amplifier provides at an output node said output voltage which has a negative variation with negative temperature.
10. A circuit according to claim 9 , wherein the offset circuit comprises a bipolar transistor connected in series with a resistive element.
11. A circuit according to claims 2 and 10, wherein the temperature dependent current from the circuit is mirrored into the second stage to flow through the resistive element of the offset circuit.
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Cited By (2)
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---|---|---|---|---|
US20140015504A1 (en) * | 2011-04-12 | 2014-01-16 | Renesas Electronics Corporation | Voltage generating circuit |
US10496122B1 (en) * | 2018-08-22 | 2019-12-03 | Nxp Usa, Inc. | Reference voltage generator with regulator system |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US6657480B2 (en) * | 2000-07-21 | 2003-12-02 | Ixys Corporation | CMOS compatible band gap reference |
US6954059B1 (en) * | 2003-04-16 | 2005-10-11 | National Semiconductor Corporation | Method and apparatus for output voltage temperature dependence adjustment of a low voltage band gap circuit |
KR20140079046A (en) * | 2012-12-18 | 2014-06-26 | 에스케이하이닉스 주식회사 | Differential amplifer |
US9753138B1 (en) * | 2016-04-13 | 2017-09-05 | Microsoft Technology Licensing, Llc | Transducer measurement |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4525663A (en) * | 1982-08-03 | 1985-06-25 | Burr-Brown Corporation | Precision band-gap voltage reference circuit |
US4902959A (en) * | 1989-06-08 | 1990-02-20 | Analog Devices, Incorporated | Band-gap voltage reference with independently trimmable TC and output |
DE4224584C2 (en) * | 1992-07-22 | 1997-02-27 | Smi Syst Microelect Innovat | Highly accurate reference voltage source |
US5352973A (en) * | 1993-01-13 | 1994-10-04 | Analog Devices, Inc. | Temperature compensation bandgap voltage reference and method |
US5519354A (en) * | 1995-06-05 | 1996-05-21 | Analog Devices, Inc. | Integrated circuit temperature sensor with a programmable offset |
US5686821A (en) * | 1996-05-09 | 1997-11-11 | Analog Devices, Inc. | Stable low dropout voltage regulator controller |
US6037833A (en) * | 1997-11-10 | 2000-03-14 | Philips Electronics North America Corporation | Generator for generating voltage proportional to absolute temperature |
US6028478A (en) * | 1998-07-13 | 2000-02-22 | Philips Electronics North America Corporation | Converter circuit and variable gain amplifier with temperature compensation |
-
2000
- 2000-05-12 GB GBGB0011545.1A patent/GB0011545D0/en not_active Ceased
-
2001
- 2001-05-10 EP EP01304206A patent/EP1156403A1/en not_active Withdrawn
- 2001-05-11 US US09/854,139 patent/US6433529B1/en not_active Expired - Lifetime
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20140015504A1 (en) * | 2011-04-12 | 2014-01-16 | Renesas Electronics Corporation | Voltage generating circuit |
US9564805B2 (en) * | 2011-04-12 | 2017-02-07 | Renesas Electronics Corporation | Voltage generating circuit |
US9989985B2 (en) | 2011-04-12 | 2018-06-05 | Renesas Electronics Corporation | Voltage generating circuit |
US20180253118A1 (en) * | 2011-04-12 | 2018-09-06 | Renesas Electronics Corporation | Voltage generating circuit |
US10289145B2 (en) * | 2011-04-12 | 2019-05-14 | Renesas Electronics Corporation | Voltage generating circuit |
US10496122B1 (en) * | 2018-08-22 | 2019-12-03 | Nxp Usa, Inc. | Reference voltage generator with regulator system |
Also Published As
Publication number | Publication date |
---|---|
EP1156403A1 (en) | 2001-11-21 |
GB0011545D0 (en) | 2000-06-28 |
US6433529B1 (en) | 2002-08-13 |
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