JPH05248962A - Semiconductor temperature sensor - Google Patents

Abstract

PURPOSE:To provide a high precision semiconductor temp. sensor which gives a high output voltage and presents lesser process dispersion. CONSTITUTION:MOS transistors 5, 6, 7 are connected with respective emitter terminals of transistors 2, 3, 4 in Darlington connection. These MOS transistors 5, 6, 7 are driven by a current mirror circuit using another MOS transistor 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor temperature sensor, and more particularly to a semiconductor temperature sensor having a MOS structure.

[0002]

2. Description of the Related Art A circuit diagram of a conventional semiconductor temperature sensor is shown in FIG.
Shown in. This circuit is disclosed in "High Sensitivity Temperature Sensor with Built-in IC (HITS)" in Sensor Technology, September 1982. By driving a PNP transistor connected in three-stage Darlington with a constant current, a voltage of V _BE which is about three times that of the output voltage terminal 1 and the ground is output, and the temperature sensitivity thereof is 11 mV / ° C.

[0003]

However, in the semiconductor temperature sensor of FIG. 2, the voltage value output to the output voltage terminal 1 is exactly about 1.5V. Normally, since V _BE is three stages, an output voltage of 1.8 V should be obtained if V _BE = 0.6V. This is because, in this circuit, the base current of the transistor 2 becomes the emitter current of the transistor 3 in the next stage, and the base current of the transistor 3 becomes the emitter current of the transistor 4, so that the base-emitter currents of the transistors 3 and 4 gradually increase. It is due to the decrease. Therefore, the V _BE voltage gradually decreases and the output voltage terminal 1
_Does not output the V _BE voltage three times higher. Further, since the base-emitter current flowing through each transistor decreases, the process variation of the temperature coefficient of V _BE also increases, so that the temperature detection accuracy deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a semiconductor temperature sensor having good temperature accuracy and high output voltage.

[0005]

To achieve the above object, the main means adopted by the present invention are as follows.
In other words, the emitter current of each transistor is
By supplying from the S-transistor and changing the channel width or channel length of these MOS transistors, the base-emitter currents flowing through the three transistors 2, 3 and 4 are made equal.

[0006]

In the semiconductor temperature sensor of the present invention, since the base-emitter currents flowing through the respective stages are made equal, the characteristics of the three transistors are made equal, and a semiconductor temperature sensor of high precision and high output voltage can be obtained.

[0007]

1 is a circuit diagram of a semiconductor temperature sensor of the present invention. The emitter terminals of the Darlington-connected PNP transistors 2, 3 and 4 are MOS transistors 5 and 6, respectively.
And 7 drains are connected respectively. Also, MO
The gates of the S transistors 5, 6, and 7 are all connected to the gate and drain of the MOS transistor 8 to form a current mirror circuit. A constant current source 9 is connected to the drain of the MOS transistor 8.

The current value flowing into the emitter terminal of the PNP transistor 2 is I ₁ . If the current amplification factor of the PNP transistor is α, the base current of the transistor 2 is I
It becomes ₁ (1-α). If the value of the current flowing through the MOS transistor 6 is αI ₁ , the current flowing into the emitter terminal of the transistor 3 becomes equal to I ₁ . Further, if the transistor 3 and the transistor 2 are formed in the same size, the current amplification factor of the transistor 3 is α. Therefore,
The base current of the transistor 3 becomes I ₁ (1-α).
Similarly, if the current value flowing in the MOS transistor 7 is αI ₁ , the current value flowing into the emitter terminal of the transistor 4 becomes equal to I ₁ . If the transistors 2, 3 and 4 are all formed to have the same size, the current amplification factors are all the same and the base-emitter currents are also the same, so that the base-emitter voltage V _BE becomes the same and the output voltage terminal becomes The V _BE voltage of 3 times is output to 1. Further, since the transistors 2, 3 and 4 have the same size, the matching characteristics of mutual characteristics are good even with respect to process variations.

Next, a method for setting the current flowing through the MOS transistor 5 as I ₁ and the currents flowing through the MOS transistors 6 and 7 as αI ₁ may be performed as follows. If the constant current value of the constant current source 9 is I _1, and the channel widths, channel lengths, and threshold voltages of the MOS transistors 5 and 8 are equal, a constant current value I ₁ flows through the MOS transistor 5. In order to pass the current of αI ₁ through the MOS transistors 6 and 7, for example, if the channel width of the MOS transistor 8 is W ₁ , the channel width of the MOS transistors 6 and 7 may be set to αW ₁ . Of course, in this state, the channel length and the threshold voltage are set equal to those of the MOS transistor 8. If the channel width W and the threshold voltage are equal, the channel length of the MOS transistor 8 is L ₁ and the channel lengths of the MOS transistors 6 and 7 are L ₁ / α.
You can set it to.

[0010]

As described above, according to the present invention, by providing means for making the base-emitter currents of Darlington-connected transistors equal, a high-accuracy semiconductor temperature sensor having a high output voltage and a small process variation. There is an effect that can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a semiconductor temperature sensor of the present invention.

FIG. 2 is a circuit diagram of a conventional semiconductor temperature sensor.

[Explanation of symbols]

 1 Output voltage terminal 2, 3, 4 PNP transistor 5, 6, 7, 8 MOS transistor 9 Constant current source

Claims (1)

[Claims] 1. A Darlington circuit formed by connecting a plurality of bipolar transistors, which are temperature-sensitive elements, a constant current source for supplying power to the Darlington circuit, and a first MOS transistor having a drain connected to the constant current source. A semiconductor temperature sensor comprising a second MOS transistor having a drain connected to an emitter terminal of a final-stage bipolar transistor of the Darlington circuit, and a source and a gate of both MOS transistors are connected to each other to form a current mirror circuit. A MOS transistor is provided corresponding to each of the bipolar transistors other than the final stage, and the drain terminal of each is connected to the corresponding emitter terminal of the bipolar transistor.
The gate terminal is also connected to the first and second MOS transistors, and their channel widths or channel lengths are such that the emitter currents of the bipolar transistors forming the semiconductor temperature sensor are all equal. A semiconductor temperature sensor characterized by being set.