JPH0569456B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature detection circuit that outputs a voltage proportional to temperature, and particularly to a semiconductor temperature detection circuit suitable for integrated circuits.

[Conventional technology]

Conventionally, as a semiconductor temperature detection circuit of this type that outputs a voltage proportional to absolute temperature, the circuit shown in Fig. 3 takes advantage of the fact that the difference in base-emitter voltage ΔV _BE of bipolar transistors with different current densities is proportional to absolute temperature. The circuit shown in the diagram is known (I.E.E.
State Circuits (IEEE J.Solid−State Ci
18, 1983, pages 707-716). The circuit in Figure 3 consists of four bipolar transistors 1, 2, 3, 4 and transistors on both sides (1, 3).
and 2, 4) with equal current, and the base-emitter voltage difference ΔV _BE between transistors 1 and 2.
The emitter area of the transistor 1 is selected to be twice that of the other transistors 2, 3, and 4.

In the circuit of FIG. 3, the currents flowing through the four bipolar transistors are equal, and as a result, the base-emitter voltages of transistors 2, 3, and 4 are all equal. On the other hand, transistor 1 is
It operates with the same current as transistors 2, 3, and 4, but its emitter area is smaller than that of transistors 2, 3, and 4.
Since the current density is twice that of transistor 2,
It will be 1/2 of that of 3 and 4. Therefore, the base-emitter voltage of transistor 1 is equal to that of transistors 2, 3, and 4, and ΔV _BE = (kT/q) ln
Only (2) is different.

In this circuit, if the base-emitter voltage of transistors 2, 3, and 4 is V _BE , then the base potential of transistor 2 is
V _BE , the potential at the base of transistor 3 is 2V _BE . On the other hand, the base potential of transistor 1 is the value obtained by subtracting the base potential V _BE of transistor 4 from the base potential 2V _BE of transistor 3, that is, V _BE
become. Since the base-emitter voltage of transistor 1 differs from the others by ΔV _BE , the emitter potential of transistor 1 is (kT/q)ln(2). That is, according to this conventional example, a voltage proportional to the absolute temperature can be detected as a voltage drop across the resistor 6. Note that if the resistance value of resistor 6 is R, the current flowing on both sides of the circuit is [(kT/q)ln
(2)]/R, which is also proportional to the absolute temperature.

By the way, many integrated detectors such as temperature detectors are currently aiming to become multi-functional and intelligent, and MOS is preferred over bipolar technology as an integrated circuit technology to achieve these goals.
There are high expectations for technology. In other words, future integrated detectors will incorporate certain semiconductor sensing circuits and other semiconductor sensing elements on the same silicon substrate, as well as amplification functions, multiplexing functions,
It is required to be equipped with an arithmetic processing function within the chip, an A/D conversion function that enables digital interface with a computer, a digital signal processing function, etc. These requirements include switch capacitor circuits, analog switches,
MOS integrated circuit technology, which has a proven track record in the field of analog/digital hybrid circuits including D conversion and microprocessors, is more suitable than bipolar technology because it has high input resistance, low power consumption, and can be integrated on a large scale. .

However, the circuit configuration of the well-known integrated temperature detection circuit shown in FIG. 3 is based on bipolar integration, and cannot be compatible with standard MOS integration processes.

As a solution to the above problems, a circuit as shown in Figure 4, which can be realized using MOS integrated circuits, has been reported (Sensors and Actuators, Vol. 6, 1984).
(2010, pp. 191-200). That is, the circuit of FIG. 4 has two diodes 11, 1 with different junction areas.
2. MOSFET 13 which acts as these current sources,
14 and MOSFET 1 constituting a bias circuit that supplies bias voltage to the MOSFETs 13 and 14.
It consists of 5 to 18. The forward current I _i of the diodes 11 and 12 is given by the following equation.

I _i =I _S A _i exp (qV _i /kT) Here, I _S represents the saturation current of the diode, A _i represents the junction area, and V _i represents the forward voltage drop. Therefore, the difference (V ₂ -V ₁ ) between the forward voltage drops V ₁ and V ₂ of the two diodes 11 and 12 in the circuit of FIG. 4 is given by the following equation.

V ₂ −V ₁ = (kT/q)ln(nA ₁ /A ₂ ) where n is the diode 11 and diode 12
This is the ratio (I ₁ /I ₂ ) of the currents I ₁ and I ₂ flowing through the current mirror, and is determined by the ratio of the aspect ratio (W/L ratio) of the MOSFETs 13 and 14 forming the current mirror. As is clear from the above equation, in the circuit of FIG. 4, a voltage proportional to the absolute temperature is obtained as the difference in forward voltage drops of two diodes operating at different current densities. P-n junction diode 1 in this conventional example
1 and 12 can be easily realized by an N-well CMOS manufacturing process using the N-well in the P-type semiconductor substrate as the cathode and the p ⁺ diffusion region as the anode.

[Problem that the invention seeks to solve]

The above describes conventional examples of semiconductor temperature detection circuits suitable for MOS integration. However, the fourth
In the circuit shown in the figure, the anode potential of diodes 11 and 12 is close to the power line voltage (ground voltage in this example), so unless the common mode input range of the amplifier circuit is very large, the potential difference between them will be amplified. The drawback was that it was difficult to do.

In addition, the temperature detection circuit shown in Figure 3 used in bipolar ICs is fundamentally based on a bipolar manufacturing process, and the collector is at a potential other than the power supply voltage, so the circuit configuration is different from the standard one.
This would have been impossible to achieve using the MOS manufacturing process.

As described above, there is no conventional semiconductor temperature detection circuit that can easily process output signals and is suitable for MOS integration.

The present invention has been made to solve the problems of the prior art described above, and its purpose is to provide a semiconductor temperature detection circuit suitable for MOS integration.

[Means for solving problems]

The present invention provides a pair of bipolar transistors whose collectors and bases are connected in common, and whose collectors are connected to a first power supply line, an inverting input terminal connected to the emitter of one of the bipolar transistors, and a non-inverting input terminal connected to the emitter of one of the bipolar transistors. is connected to the other emitter via a first resistor, and has an output terminal connected to the commonly connected base; the non-inverting input terminal of the first operational amplifier; second and third resistors respectively connected between the inverting input terminal and the second power supply line; and the inverting input terminal being connected to the output terminal and the voltage application terminal via fourth and fifth resistors, respectively. and a second operational amplifier having a non-inverting input terminal connected to a connection point between the first and second resistors.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 21 and 22 are a pair of bipolar transistors whose collectors and bases are connected in common, 31, 32 and 33 are resistors, and 20 and 40
is an operational amplifier, and is configured to take out the voltage obtained at the connection point of the resistor 31 and the resistor 32 via a non-inverting amplifier circuit consisting of an operational amplifier 40 and resistors 41 and 42.

The collectors and bases of the pair of bipolar transistors 21 and 22 in this embodiment are connected in common and led to the power supply voltage supply terminal 23 and the output terminal 24 of the operational amplifier 20, and the emitters are connected to the resistor 33 and the resistor 31, respectively. 32 to the ground terminal. On the other hand, the operational amplifier 20
The inverting input terminal 25 is connected to the emitter of the transistor 21, and the non-inverting input terminal 26 is connected to the midpoint between the resistors 31 and 32, which are connected to the emitter of the transistor 22. Then, the midpoint voltage of the resistor 31 and the resistor 32 is the voltage between the operational amplifier 40 and the resistor 41.
and 42, where it is amplified and taken out from the output terminal of the amplifier 40. Further, an appropriate voltage is applied to the voltage application terminal 43 via a resistor 41 and a resistor 42 to adjust the offset of the output voltage.

Next, the temperature characteristics of the voltage obtained at the connection point 26 between the resistor 31 and the resistor 32 in this embodiment will be explained. In the circuit shown in FIG. 1, the base-emitter voltage of transistors 21 and 22 is set to Vbe ₁
and Vbe ₂ , the collector currents are I ₁ and I ₂ , and the resistor 3
The resistance values of 1, 32, and 33 are R ₁ , R ₂ , R ₃ respectively
shall be. The operational amplifier 20 in this embodiment amplifies the voltage difference between the non-inverting input terminal and the inverting input terminal by its high open-circuit gain and input resistance,
As a result, the output voltage of the amplifier ₂₀ , that is, the transistor ₂
The voltage at the base terminals 24 of 1 and 22 is controlled.
Therefore, the commonly connected transistors 21,
Letting the base voltage of 22 be _VB , the voltage relationship of each part of the circuit is expressed by the following equation.

V _B = Vbe ₁ + I ₂ · R ₂ Here, since I ₂ = (Vbe ₁ − Vbe ₂ )/R ₁ , the connection point 26 between the resistors 31 and 32
The voltage V _M obtained at is given by the following equation.

_{V M} = I ₂ · R ₂ = (R ₂ / R ₁ ) · ΔV _BE In the above formula, ΔV _BE is the difference between Vbe ₁ and Vbe 2, and Vbe ₁ and Vbe ₂ are respectively Vbe ₁ = (kT/ q)・ln(I ₁ /I _S1 ) Vbe ₂ = (kT/q)・ln(I ₂ /I _S2 ) k: Boltzmann constant T: Absolute temperature q: Electron charge I _S1 : Saturation current I of transistor 21 _S2 : Since it is expressed as the saturation current of the transistor 22, ΔV _BE is given by the following equation.

ΔV _BE = (kT/q)・ln(I ₁ I _S2 /I ₂ I _S1 ) = (kT/q)・ln(R ₂ I _S2 /R ₃ I _S1 ) In other words, in this example, the resistor 31 and The voltage V _M obtained at the connection point 26 with the resistor 32 is proportional to the absolute temperature. The voltage V _M is amplified by a non-inverting amplifier circuit consisting of an operational amplifier 40 and resistors 41 and 42. Now, resistor 41 and resistor 42
Assuming that the resistance values of are R ₁₁ and R ₁₂ and the voltage applied to the voltage application terminal 43 is V _R , the output voltage V ₀ of this detection circuit obtained at the output terminal of the operational amplifier 40 is given by the following equation.

V ₀ = (1+R ₁₂ /R ₁₁ )・(R ₂ /R ₁ )・(kT/q)・ln
(R ₂ I _S2 /R ₃ I _S1 )−(R ₁₂ /R ₁₁ )・_V RAs is clear from the above equation, the detection circuit in this embodiment applies the desired voltage to the voltage V _M proportional to the absolute temperature. The output voltage V ₀ can be obtained by adding the sensitivity coefficient (1+R ₁₂ /R ₁₁ ) and the offset voltage=( _{R 12} /R ₁₁ )·VR. Therefore, according to this embodiment, it is possible to extract an output voltage corresponding not only to absolute temperature but also to Celsius or Fahrenheit, which are generally widely used.

The major features of the circuit configuration in this example are as follows:
The point is that the collectors of bipolar transistors 21 and 22 are commonly connected to a power supply voltage supply terminal 23. Conventional temperature detection circuits using bipolar transistors are not configured so that the collector is connected to a common terminal (highest or lowest potential in the circuit) such as a power supply voltage supply terminal or a connection terminal. It was not possible to fabricate transistors that would allow this connection using standard MOS processes.

On the other hand, since the transistors 21 and 22 used in this embodiment may have a common collector, as shown in the cross section of FIG. , can be realized by a standard MOS process as a vertical bipolar transistor having the P-well region 35 as a base and the n ⁺ region 36 for forming the source and drain of an N-channel transistor as an emitter. Also, the resistors 31, 32, 3 in FIG.
For example, silicon chromium (SiCr)
Trimming is possible and has good precision, such as thin film resistors.
Resistance elements with small temperature coefficients can be easily integrated.

Further, in this embodiment, the operating point of the transistor can be appropriately selected by setting the resistance values of the resistors 31, 32, and 33, and the voltage proportional to the absolute temperature obtained at the connection point of the resistors 31 and 32 is Since the output signal is amplified (sensitivity adjusted) and offset adjusted by a non-inverting amplifier circuit consisting of an operational amplifier 40 and resistors 41 and 42, post-processing of the output signal becomes extremely easy.

Therefore, according to this embodiment, it is possible to obtain an excellent semiconductor temperature detection circuit in which post-processing of the output signal is easy and is suitable for MOS integration.

In the above embodiment, a P-type semiconductor substrate using an N-type semiconductor substrate is used.
Although the bipolar transistor is an n-p-n type assuming a well CMOS manufacturing process, a similar circuit using a p-n-p transistor can also be used in an N-well CMOS manufacturing process using a P-type semiconductor substrate. is possible.

〔Effect of the invention〕

As described above, according to the present invention, all the drawbacks of the above-mentioned conventional techniques are eliminated, and an extremely useful semiconductor temperature detection circuit suitable for MOS integration is realized. The temperature detection circuit according to the present invention contributes to making the semiconductor detector intelligent by combining it with a microcomputer, and its effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing an example of the structure of a vertical bipolar transistor which is a component of this embodiment, and FIGS. 3 and 4 are FIG. 3 is a circuit diagram showing a conventional example of a semiconductor temperature detection circuit. 20, 40... operational amplifier, 21, 22... bipolar transistor, 23... current voltage supply terminal, 24... common base terminal, 25... inverting input terminal, 26... non-inverting input terminal (temperature detection circuit output terminal), 31, 32, 33, 41, 42...resistance element, 34...N-type semiconductor substrate, 35...P-
Well region, 36...n ⁺ region, 43... Voltage application terminal.

Claims (1)

[Claims] 1 A pair of bipolar transistors whose collectors and bases are connected in common, and whose collectors are connected to a first power supply line; an inverting input terminal is connected to the emitter of one of the bipolar transistors, and a non-inverting input terminal is connected to the emitter of one of the bipolar transistors. a first operational amplifier whose output terminal is connected to the other emitter through one resistor and whose output terminal is connected to the commonly connected base; and the non-inverting input terminal and the inverting input of the first operational amplifier. second and third resistors respectively connected between the terminal and the second power supply line; and the inverting input terminal connected to the output terminal and the voltage application terminal via fourth and fifth resistors, respectively; and a second operational amplifier having a non-inverting input terminal connected to a connection point between the first and second resistors.