Four current transistor temperature sensor and method
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United States of America Patent
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Apr 29, 2003
Grant Date -
N/A
app pub date -
Apr 17, 2001
filing date -
Apr 17, 2001
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
A four current transistor temperature sensor comprises a p-n junction, preferably the base-emitter junction of a bipolar transistor, which is driven with four different currents in a predetermined sequence. Each of the four currents induces a respective base-emitter voltage, which is measured. The temperature of the transistor is calculated based on the values of the four driving currents and the four measured base-emitter voltages. The four driving currents (I1, I2, I3 and I4) are preferably arranged such that I1=2*I3, I2=2*I4, I1/I2=A and I3/I4=A, where A is a predetermined current ratio. I1 and I2 produce respective base-emitter voltages which are subtracted from each other to produce .DELTA.V.sub.be1, and I3 and I4 produce respective base-emitter voltages which are subtracted from each other to produce .DELTA.V.sub.be2. When so arranged, the difference between .DELTA.V.sub.be1 and .DELTA.V.sub.be2 is entirely due to the effect of series base and emitter resistances r.sub.b and r.sub.e. Therefore, the .DELTA.V.sub.be1 -.DELTA.V.sub.be2 value provides a correction factor which enables temperature measurement errors due to r.sub.b and r.sub.e to be eliminated.
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