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An apparatus and method for canceling variations in the beta for a bipolar junction transistor so that the diode equation can be employed to accurately measure the temperature of the transistor based at least in part on a ratio of two target collector currents and two measurements of the base-emitte

An apparatus and method for canceling variations in the beta for a bipolar junction transistor so that the diode equation can be employed to accurately measure the temperature of the transistor based at least in part on a ratio of two target collector currents and two measurements of the base-emitter voltage of the transistor. If the determined collector current of the transistor is relatively equivalent to one of the first and second target collector currents, the transistor's base-emitter voltage is measured and stored. An analog feedback circuit can be employed to change the determined collector current to be relatively equivalent to the first and second target collector currents. The analog feedback circuit can include an optional sample and hold component to further reduce power consumption and reduce noise. A digital circuit can be employed to change the determined collector current to be relatively equivalent to the first and second target collector currents. Additionally, the transistor can be remotely located in another integrated circuit.

대표청구항 ▼

What is claimed as new and desired to be protected by Letters Patent of the United States is: 1. A method for determining the temperature of a bipolar junction transistor, which has an emitter terminal that carries an emitter current Ie, a base terminal that carries a base current Ib, and a collect

What is claimed as new and desired to be protected by Letters Patent of the United States is: 1. A method for determining the temperature of a bipolar junction transistor, which has an emitter terminal that carries an emitter current Ie, a base terminal that carries a base current Ib, and a collector terminal that carries a collector current Ic, and wherein said currents are related by Ie=Ib+Ic, the method comprising the steps of: applying a first emitter current (Ie1) to the emitter terminal of said transistor, wherein said first emitter current (Ie1) comprises a first base current component (Ib1) and a first collector current component (Ic1) with the relationship Ie1=Ib1+Ic1, adjusting the first emitter current (Ie1) while sensing the first base current (Ib1) at the base terminal until a sensed first base current (Ib1) is substantially equal to a different between the adjusted first emitter current (Ie1) and a first predetermined target collector current (ICT1), sensing a first voltage (Vbe1) between the base and emitter terminals of said transistor while said adjusted first emitter current (Ie1) is applied to said emitter terminal, applying a second emitter current (Ie2) to the emitter terminal of said transistor, wherein said second emitter current (Ie2) comprises a second base current component (Ib2) and a second collector current component (Ic2) with the relationship Ie2=Ib2+Ic2, adjusting the second emitter current (Ie2) while sensing the second base current (Ib2) at the base terminal until a sensed second base current (Ib2) is substantially equal to a difference between the adjusted second emitter current (Ie2) and a second predetermined target collector current (ICT2), with the first and second target collector currents (ICT1, ICT2) differing in magnitude, sensing a second voltage (Vbe2) between the base and emitter terminals of said transistor while said adjusted second emitter current (Ie2) is applied to said emitter terminal, and determining the temperature of said transistor based, at least in part, on a difference between said first and second voltages (Vbe1 and Vbe2). 2. The method of claim 1, wherein the determining the temperature is further based on said first and second collector currents (Ic1 and Ic2) and said first and second voltages (Vbe1 and Vbe2) as used in the following: where T is absolute temperature, η is the transistor coefficient, k is Boltzmann's constant, and q is the electron charge. 3. The method of claim 1, further comprising biasing said transistor above a common mode voltage, with the common mode voltage having a magnitude being determined by measurement circuitry having an associated common mode operating voltage, with the measurement circuitry being used in carrying out the method of determining the temperature. 4. The method of claim 1, wherein the first and second predetermined target collector currents (ICT1) and (ICT2) differ by at least an order of magnitude. 5. A method for determining the temperature of a bipolar junction transistor, which has an emitter terminal that carriers an emitter current Ie, a base terminal that carries a base current Ib, and a collector terminal that carries a collector current Ic, and wherein said currents are related by Ie=Ib+Ic, the method comprising the steps of: applying a first emitter current (Ie1) to the emitter terminal of said transistor, wherein said first emitter current (Ie1) comprises a first base current component (Ib1) and a first collector current component (Ic1) with the relationship Ie1=Ib1+Ic1, adjusting the first emitter current (Ie1) while sensing the first base current (Ib1) at the base terminal until a sensed first base current (Ib1) is substantially equal to a difference between the adjusted first emitter current (Ie1) and a first target collector current (ICT1), sensing a first voltage (Vbe1) between the base and emitter terminals of said transistor while said adjusted first emitter current (Ie1) is applied to said emitter terminal, applying a second emitter current (Ie2) to the emitter terminal of said transistor, wherein said second emitter current (Ie2) comprises a second base current component (Ib2) and a second collector current component (Ic2) with the relationship Ie2=Ib2+Ic2, adjusting the second emitter current (Ie2) while sensing the second base current (Ib2) at the base terminal until a sensed second base current (Ib2) is substantially equal to a difference between the adjusted second emitter current (Ie2) and a second target collector current (ICT2), with the first and second target collector currents (ICT1, ICT2) having a predetermined ratio N greater than one, sensing a second voltage (Vbe2) between the base and emitter terminals of said transistor while said second adjusted emitter current (Ie2) is applied to said emitter terminal, and determining the temperature of said transistor as a function of said ration N and a different between said first and second voltages (Vbe1 and Vbe2). 6. The method of claim 5, wherein the determining the temperature utilizes the following equation: wherein T is absolute temperature, η is the transistor coefficient, k is Boltzmann's constant, and q is the electron charge. 7. The method of claim 5, further comprising biasing said transistor above a common mode voltage, with the common mode voltage having a magnitude being determined by measurement circuitry having an associated common mode operating voltage, with the measurement circuitry being used in carrying out the method of determining the temperature. 8. The method of claim 5 wherein ratio N is at least 10. 9. Apparatus for use in measuring temperature of a bi-polar transistor, said apparatus including: emitter circuitry to be coupled to an emitter electrode of the bi-polar transistor, with the emitter circuitry being operative to provide an adjustable emitter current to the bi-polar transistor; base circuitry to be coupled to a base electrode of the bi-polar transistor, with the base circuitry being operative to provide a base signal indicative of a magnitude of the base current of the bi-polar transistor; voltage sense circuitry to be coupled to the emitter and base electrodes of the bi-polar transistor; and control circuitry operative to cause the emitter circuitry to adjust the emitter current of the bi-polar transistor in response to the base signal so that the bi-polar transistor collector current is at a first collector current value, to cause the voltage sense circuitry to sense a base-emitter voltage of the bi-polar transistor when the collector current is at the first collector current value, to then cause the emitter circuitry to adjust the emitter current of the bi-polar transistor in response to the base signal so that the bi-polar transistor is at a second collector current value different from the first collector current value and to cause the voltage sense circuitry to sense the base-emitter voltage of the bi-polar transistor when the collector current is at the second collector current value. 10. The apparatus of claim 9 wherein the emitter circuitry is further operative to provide an emitter signal indicative of bi-polar transistor emitter current, wherein the apparatus further includes target current circuitry to provide a target signal indicative of the first collector current value and wherein the control circuit is further operative to cause the emitter circuitry to adjust the emitter current in response to the base signal, the emitter signal and the target signal so that the bi-polar transistor collector current is at the first collector current value. 11. The apparatus of claim 10 wherein the target current circuitry is further operative to adjust the target signal in response to a sensed characteristic of the bi-polar transistor. 12. The apparatus of claim 11 wherein the sensed characteristic includes the bi-polar transistor current gain, with a relatively low current gain causing the target signal to indicative a relatively low first collector current value and with a relatively high current gain causing the target signal to indicate a relatively high collector current value. 13. A method for use in measuring temperature of a bi-polar transistor: (a) providing emitter current to the bi-polar transistor; (b) determining the bi-polar transistor collector current by sensing bi-polar base current at a base terminal of the bi-polar transistor together with monitoring the bi-polar emitter current, with the determining being carrier out independent of any sensing of bi-polar collector current at any collector terminal of the bi-polar transistor; (c) adjsuting the emitter current so as to produce first and second bi-polar transistor collector currents of differing magnitudes; and (d) sensing a first bi-polar transistor base-emitter voltage when the transistor is conducting the first collector current and sensing a second bi-polar transistor base-emitter voltage when the transistor is conducting the second collector current; and determining the temperature of the transistor based, at least in part, on the first and second base-emitter voltages. 14. The method of claim 13 wherein determining the of the bi-polar transistor is based, at least in part, on a difference between the first and second base-emitter voltages. 15. The method of claim 14 wherein the determining a temperature is further based, at least in part, on a ratio of the first and second bi-polar collector currents. 16. The method of claim 13 further including producing an emitter signal indicative of the bi-polar emitter current, a base signal indicative of the bi-polar base current and a target signal indicative of a desired bi-polar collector current and wherein the base and emitter signals are used in the determining of the bi-polar collector current and wherein the target signal is used in the adjsuting the emitter current so as to produce the first bi-polar transistor collector current. 17. The method of claim 16 wherein the target signal is indicative of the first bi-polar collector current, wherein the producing a target signal includes sensing a characteristic of the bi-polar transistor and adjusting the target signal in response to the characteristics. 18. The method of claim 17 wherein the characteristic sensed includes the current gain of the bi-polar transistor, with the target signal being set to a value indicative of a relatively low target collector current magnitude when a relatively low current gain is sensed and with the target signal being set of another value indicative of a relatively high target collector current magnitude when a relatively high current gain is sensed. 19. A method for use in measuring temperature of a bi-polar transistor comprising: (a) providing a first adjustable emitter current to an emitter terminal of the bi-polar transistor; (b) sensing a first base current at a base electrode of the bi-polar transistor while adjsuting the first adjustable emitter current so as to produce a first collector current in the bi-polar transistor substantially equal in magnitude to a first collector current value; (c) providing a second adjustable emitter current to the emitter terminal of the bi-polar transistor; (d) sensing a second base current at the base electrode of the bi-polar transistor while adjsuting the second adjustable emitter current so as to produce a second collector current in the bi-polar transistor substantially equal in magnitude to a second collector current value, with the first and second collector current values differing in magnitude; and (e) determining a temperature of the bi-polar transistor based, at least in part, on a ratio of the first and second collector current values. 20. The method of claim 19 further including sensing a first base-emitter voltage of the bi-polar transistor when the bi-polar transistor is conducting the first collector current substantially equal in magnitude to the first collector current value and further including sensing a second base-emitter voltage of the bi-polar transistor when the bi-polar transistor is conducting the second collector current substantially equal in magnitude to the second collector current values, with the determining being further based, at least in part, on a difference in magnitude of the first and second sensed base-emitter voltages. 21. The method of claim 19 wherein the determining the temperature is carried out independent of directly sensing current at any collector terminal of the bi-polar transistor. 22. The method of claim 19 wherein the sensing a first base current includes producing a base signal indicative of the bi-polar transistor base current, with the base signal being used when sensing the first base current while adjusting the first adjustable emitter current so as to produce the first collector current value. 23. The method of claim 22 wherein the base signal is a current signal having a magnitude that is substantially equal to a magnitude of the bi-polar transistor base current. 24. The method of claim 22 wherein the base signal is produced using a current mirrior circuit having a current mirror input coupled to the base electrode of the bi-polar transistor. 25. The method of claim 22 wherein the adjusting the first adjustable emitter current includes producing an emitter signal indicative of the bi-polar emitter current, with the emitter signal being used when adjsuting the first adjustable emitter current so as to produce the first collector current value. 26. The method of claim 25 wherein the emitter signal is another current signal having a magnitude that is substantially equal to a magnitude of the bi-polar transistor emitter current. 27. The method of claim 19 wherein the adjsuting the first adjustable emitter current so as to produce a first collector current in the bi-polar transistor substantially equal in magnitude to a first collector current includes producing a target signal indicative of the first collector current value. 28. The method of claim 27 further including producing a base signal indicative of the bi-polar transistor base current and producing an emitter signal indicative of the bi-polar transistor emitter current and wherein the adjsuting the first adjustable current so as to product a first collector current in the bi-polar transistor substantially equal in magnitude to a first collector current value is carried out using the base signal, the emitter signal and the target signal. 29. The method of claim 28 wherein the adjsuting the first adjustable current so as to product a first collector current in the bi-polar transistor substantially equal in magnitude to a first collector current value by changing the emitter current until a magnitude of the emitter signal is substantially equal to a sum of the base signal and the target signal. 30. The method of claim 27 wherein the producing the target signal includes sensing characteristics of the bi-polar transistor and adjsuting the target signal in response to the characteristics. 31. The method of claim 30 wherein the characteristic sensed includes the current gain of the bi-polar transistor, with the target signal being set to a value indicative of a relatively low target collector current magnitude when a relatively low current gain is sensed and with the target signal being set to another value indicative of a relatively high target collector current magnitude when a relatively high current gain is sensed. 32. The method of claim 30 wherein the adjsuting the target signal is carried out prior to the adjsuting the first adjustable emitter current so as to produce a first collector current substantially equal in magnitude to the first collector current value.