JPH0456935B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature sensor circuit, and in particular, bipolar transistors are manufactured in the same process as a MOS process, and bipolar transistors and MOS
The present invention relates to a temperature sensor circuit composed of transistors.

[Conventional technology]

Conventionally, many of this type of temperature sensor circuits have been constructed only from bipolar transistors.
In recent years, with advances in process technology, it has become possible to fabricate MOS transistors and bipolar transistors on the same substrate. Normally, there are two ways to create a bipolar transistor using a MOS process: one is to add layers such as a buried layer, and the other is to create a bipolar transistor using only the MOS process. The former method is undesirable as it complicates the process and increases the number of process steps, so currently, bipolar transistors are often created using the source or drain junction of the MOS transistor instead of using the gate in the MOS process as in the latter method. . Since this process technology uses the substrate as the collector, all bipolar transistors have a common collector grounded.

Conventionally, a temperature sensor circuit that can be manufactured using a MOS process is as shown in FIG. Darlington connected bipolar transistors Q _k1 , Q _k2
Among them, the emitter of bipolar transistor Q _k2 is connected to a constant current circuit I _k1 consisting of a MOS transistor.
By connecting the emitter of the bipolar transistor Q _k2 to the output terminal, the temperature change in the base-emitter voltage of the bipolar transistors Q _k1 and Q _k2 is used as a temperature sensor.

[Problem that the invention seeks to solve]

However, since the above-mentioned conventional temperature sensor circuit is configured with a Darlington connection, it has a disadvantage that the variation in current gain β is synergistically large with respect to the variation in output sensitivity. Therefore, in order to suppress variations in the current gain β, it is necessary to make the base width of the base region relatively thick and accurately control it, which has the disadvantage of complicating the process.

An object of the present invention is to provide a temperature sensor circuit having a circuit configuration that can be manufactured using a normal MOS process.

[Means for solving problems]

According to the present invention, n (n is an integer of 2 or more) bipolar transistors each having a collector connected to a first constant potential point, and at least n bipolar transistors each having a collector connected to a second constant potential point, a constant current circuit composed of MOS transistors that outputs a current, each emitter of the n bipolar transistors is connected to receive one constant current, and the base of the first bipolar transistor is The base of the i-th (i is an integer from 2 to n) bipolar transistor is connected to its own collector, and the base of the i-th bipolar transistor is connected to the emitter of the i-1-th bipolar transistor, and the output is output from the emitter of the n-th bipolar transistor. A temperature sensor circuit is obtained.

As described above, since the temperature sensor circuit of the present invention is not connected in Darlington, the variation in the output voltage due to the temperature change can be kept small even when the current gain β changes, and the process is not complicated.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of one embodiment of a temperature sensor circuit according to the present invention.

n (n1) bipolar transistors Q _p1
, Q _p2 ,…, the collectors of Q _po are commonly connected,
A constant current circuit I p1 , I _p2 , which is set as a negative voltage (ground) terminal 2 and constituted by a MOS transistor is connected to the emitter of each bipolar transistor Q _p1 , Q _p2 , ..., _{Q po} .
..., I _po are connected respectively. The base of the bipolar transistor Q _p1 in the first stage is diode-connected to the collector, and the bases of the bipolar transistors Q _p2 , . . . , Q _po in the next stage are connected to the emitters of the bipolar transistors in the previous stage. The output terminal 3 is taken out from the emitter of the n-th stage bipolar transistor _Qpo .

The voltage between the base and emitter of a bipolar transistor is a certain voltage V _BE produced by passing current through a constant current circuit, and this voltage V _BE changes depending on the temperature.
It shows the characteristics expressed by equation (1).

V _BE ≒kT/qln(I/ _Is )...(1) where, k: Boltzmann's constant q: Unit charge T: Absolute temperature _Is : Saturation current I: Current flowing through the bipolar transistor Current I flowing through the bipolar transistor When driven by a constant current circuit, the saturation current I _s can be ignored by taking the logarithm of the temperature change, and the voltage V _BE is almost monotonically proportional to the temperature T. The bipolar transistors Q _p1 , Q _p2 ,...
The base-emitter voltage of Q _po is V _BE1 ,
Let V _BE2 ,...,V _BEo and set the potential of negative power supply terminal 2 to 0V
Then, the output voltage V _OUT is V _OUT = V _BE1 + V _BE2 +...+V _BEo (2).

Here, each base-emitter voltage V _BE1 ,
V _BE2 , ..., V _BEo change depending on the temperature T. In other words, by substituting equation (1) into equation (2), the output voltage at temperature T〓 is V _OUT (T)≒kT/qln (I _p1 /I _s ) + kT/qln (I _p2 /I _s
)＋…＋kT／qln( _Ipo ／ _Is )＝kT／q(ln( _Ip1 ／ _Is )
+ln (I _p2 / I _s ) +… + ln (I _po / I _s ))
...(3), which shows a temperature characteristic that is a monotonic function of temperature T. FIG. 2 shows an embodiment using an NPN transistor, and the above principle holds true in the same way.

FIGS. 3 and 4 are circuit diagrams of specific embodiments using a MOS process. FIG. 3 is a circuit diagram of a temperature sensor circuit using a P-type substrate.
Figure 5 shows the result of MOS process using P-type substrate 4.
FIG. 2 is a cross-sectional view of a PNP vertical bipolar transistor. The collector 5 is of the same P type as the substrate 4, and is always at the same potential as the substrate 4. P type board 4
An N well 8 is created inside, and this becomes a base area and is taken out from the base terminal 7. Also, N well 8
A P-type region is formed inside, and this becomes the emitter 6. In such a process, the collector is always connected to the substrate, so the potential is the same as that of the substrate. Usually, P
When using a shaped substrate, the substrate is connected to a negative potential (ground). In Figure 3, since a P-type substrate is used as mentioned above, the collectors are connected in common and the circuit configuration is connected to the negative power supply 2, and the number of bipolar transistors is 4 (n = 4). This is a diagram. P channel MOS transistor M _A2 , M _A3
A current mirror circuit is constituted by the MOS resistor and the P-channel MOS transistor M _A1 , and the P-channel MOS transistors M _p1 , M _p2 ,
M _p3 and M _p4 each constitute a constant current circuit through which a current proportional to the current flowing through the P-channel MOS transistor M _A1 flows. If P channel MOS
If the currents flowing through transistors M _p1 to _{M p4} are constant with respect to temperature, then from equation (3), the output voltage change ΔV _OUT per 1°C is ΔV _OUT 2.5 mV x 4 = 10 mV ... (4) .

FIG. 6 is a characteristic diagram of the temperature sensor circuit of FIG. 3. The reason why the output voltage curves slightly with temperature changes is because the low current circuit using MOS transistors fluctuates slightly with temperature, but a characteristic that can be considered almost linear is obtained.

Figure 4 shows a temperature sensor circuit using an N-type substrate, in which the collectors are commonly connected and the positive potential terminal 1 is an NPN bipolar transistor and N-channel MOS transistors M _o1 , M _o2 , M _o3 , M _o4 The third
Characteristics similar to those shown in the figure can be obtained.

Since the circuit configurations shown in FIGS. 3 and 4 do not use a connection such as a Darlington connection, it is possible to suppress variations in the output voltage due to temperature changes even when the current gain β changes.

〔Effect of the invention〕

As explained above, the present invention has n constant current circuits made by a MOS process and configured by n bipolar transistors and MOS transistors whose collectors are connected in common, and a first bipolar transistor. The base and collector are connected, the base of the i-th bipolar transistor is connected to the emitter of the (i-1)-th bipolar transistor, and each of the constant current circuits is connected to the emitter of the n bipolar transistors. By creating bipolar transistors using a MOS process, a temperature sensor circuit can be realized with a simple circuit configuration without the need for complex structures or process additions.Furthermore, it is possible to realize temperature sensor circuits with a simple circuit configuration, and the amount of temperature change in the output voltage can be controlled even against variations due to process fluctuations. This has the effect of reducing variations.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram using the PNP bipolar transistor of the present invention and a constant current circuit, and Figure 2 is an NPN
A circuit diagram using a bipolar transistor and a constant current circuit, Figure 3 shows a PNP bipolar transistor, an N-channel MOS transistor, and a P-channel MOS
Figure 4 shows a specific constant current circuit composed of an NPN vertical transistor, an N-channel MOS transistor, and a P-channel MOS transistor. The circuit diagram shown in Figure 5 was created using the MOS process.
FIG. 6 is a cross-sectional view of a PNP bipolar transistor, FIG. 6 is a diagram showing the characteristics shown in FIG. 3, and FIG. 7 is a circuit diagram of a conventionally used temperature sensor circuit. 1...Positive power supply terminal, 2...Negative power supply terminal, 3...
Output terminal, Q _p1 , Q _p2 ,…, Q _p(o-1) , Q _po …PNP
Bipolar transistor, Q _o1 , Q _o2 ,...,
Q _o(o-1) , Q _oo ……NPN bipolar transistor,
I _p1 , I _p2 ,..., I _p(o-1) , I _po ... Constant current circuit composed of MOS transistors, I _o1 , I _o2 ,...,
I _o(o-1) , I _oo ... Constant current circuit composed of MOS transistors, M _A1 , M _{A2 , M p1 ,} M _p2 , M _p3 ,
M _p4 ……P channel MOS transistor, M _A3 ……
N-channel MOS transistor, M _B2 , M _B3 ,
M _o1 , M _o2 , M _o3 , M _o4 ... N channel MOS transistor, M _B1 ... P channel MOS transistor, 4 ... Substrate, 5 ... Collector terminal, 6 ... Emitter terminal, 7 ... ...Base terminal, 8...N well (base region).

Claims (1)

[Claims] 1. n bipolar transistors (n is an integer of 2 or more) whose collectors are each connected to a first constant potential point, and at least n bipolar transistors whose collectors are connected to a second constant potential point, respectively.
a constant current circuit composed of MOS transistors that outputs constant currents, and each emitter of the n bipolar transistors is connected to receive one of the n constant currents,
And the base of the first bipolar transistor is connected to its collector, and the base of the first bipolar transistor is connected to the collector of the first bipolar transistor,
A temperature sensor circuit characterized in that the bases of the bipolar transistors (an integer greater than or equal to n and less than or equal to n) are connected to the emitters of the i-1th bipolar transistors, and the output is obtained from the emitters of the nth bipolar transistors.