Temperature sensor apparatus
View Patent ↗A temperature sensor apparatus comprises a pair of parallel circuit branches each including a pn semiconductor junction coupled in series to an impedance. The pn semiconductor junctions have different cross-sectional areas. An amplification stage comprises a CMOS input stage coupled respectively across each pn semiconductor junction and a FET transistor output stage (coupled to a load impedance) that generates an amplified output signal corresponding to the pn semiconductor junction temperature.
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 1 and D 2 , respectively;
a second branch including third and fourth series connected diodes with predetermined areas D 3 and D 4 , respectively;
where
D1
D3
=
D4
D2
,
and D 1 ≠D 2 ,
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.
2. The circuit according to claim 1 , wherein the resistors of the first and second branch include:
(a) first and second resistors of the first branch respectively connected between the first supply rail and an electrode of a first polarity of the first diode, and between the second supply rail and an electrode of a second polarity of the second diode, and
(b) third and fourth resistors of the second branch respectively connected between the first supply rail and an electrode of the first polarity of the third diode, and between the second supply rail and an electrode of the second polarity of the fourth diode.
3. The circuit according to claim 2 , wherein the first and second resistors are connected to the first and second diodes so all the current flowing through the first resistor flows only through the first diode and all the current flowing through the second resistor flows only through the second diode.
4. The circuit according to claim 3 , wherein the third and fourth resistors are connected to the third and fourth diodes so all the current flowing through the third resistor flows only through the third diode and all the current flowing through the fourth resistor flows only through the fourth diode.
5. The circuit according to claim 1 , wherein the resistors of the first and second branches include a first resistor connected between the first supply rail and first polarity electrodes of the first and third diodes.
6. The circuit according to claim 1 , wherein the resistors of the first and second branches include a second resistor connected between the second supply rail and second polarity electrodes of the second and fourth diodes.
7. The circuit according to claim 1 , wherein the resistive impedance includes a first resistor connected therebetween the first and second source drain paths and a second resistor connected between one of the source drain paths and one of the supply rails.
8. The circuit according to claim 7 , further including a further resistor for damping oscillations, the further resistor being connected in shunt with to the first resistor.
9. The circuit according to claim 1 , wherein D 1 =D 4 and D 2 =D 3 .
10. The circuit according to claim 1 , wherein D 1 =8×D 2 and D 4 =8×D 3 .