Patent ID: 6995588
Filing Date: 2006-02-07
Classification: G01K

Abstract:
1. A temperature sensor circuit comprising: first and second opposite voltage supply rails; a first branch including first and second series connected diodes having pn junctions with predetermined areas D a second branch including third and fourth series connected diodes with predetermined areas D where  and D the first and second branches including resistors connected to supply current flowing between the rails to the first, second, third and fourth diodes, the diodes being poled to be forward biased in response to power being applied across the rails, the diodes and resistors of the branches being connected to the rails so a first current flows through the first and second diodes and a second current flows through the third and fourth diodes in response to power being applied across the rails, the first and second branches respectively including first and second taps between the first and second diodes and between the third and fourth diodes; first and second operational amplifiers having (a) first and second opposite polarity input terminals respectively connected to be responsive to the voltage at the first and second taps and (b) first and second output terminals, respectively; and a third branch including (a) a first field effective transistor of a first conductivity type having a gate electrode connected to be responsive to voltage at the first output terminal and a first source drain path, (b) a second field effect transistor of a second conductivity type having a gate electrode connected to be responsive to the voltage at the second output terminal and a second source drain path connected in series with first source drain path, the third branch including a resistive element connected in series with the first and second source drain paths, the third branch being connected across the first and second voltage supply rails, the resistive element being connected in the third branch so an output signal derived in response to current flowing in the resistive element in response to power being supplied to the first and second rails is determined by the temperature of the circuit.