JPH079062Y2 - Temperature sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a temperature sensor for measuring temperature using a transistor, and more particularly to a temperature sensor improved so as to obtain a temperature signal in the state of an alternating voltage.

<Prior Art> FIG. 3 shows the configuration of a first conventional temperature sensor which is the basis of the improvement of the present invention.

Non-inverting input terminal (+) of the common potential point inverting input of the operational amplifier Q ₁ connected to COM (-) and the collector base of the transistor Q ₂ to which are connected to the common potential point COM between the output terminal And the emitter is connected.

Further, the power source E is connected to the inverting input terminal (-) via the resistor R _1.
A constant current I _c is input from the output terminal of the operational amplifier Q ₁ to obtain the base-emitter voltage −V _be of the transistor Q ₂ .

The temperature is applied to the transistor Q ₁ and the temperature is measured from the base-emitter voltage V _be which changes correspondingly.

Constant current I _c and the transistor to Q ₁ base / emitter voltage when a current of a constant current I _c = E / R ₁ in the transistor Q ₁ collector
The relationship with V _be is given by the following equation from the theory of diffusion current.

_{I c = (αTr / ε)} exp (-qV go / kT) [exp (qV be / kT) -1] ... (1) where, alpha is a constant determined by such base width of the transistor, r is the base region A constant determined by temperature dependence of mobility of minority carriers, V _go is an extrapolated value of the energy Galp of silicon at 0 ° K (about 1.1 to 1.2 V), k / q is Boltzmann's constant and electron Charge ratio (= 8
6.1706 μV / K), ε is the ionization coefficient.

If ε = 1 in the range where the temperature T is low and V _be / kT << 1 holds, the equation (1) becomes simple and V _be can be approximated as follows.

_{V be = V go - (kT} / q) ln (αTr / I c) ... (2) Here, when the constant I _c, the relation of V _be for temperature T is close to a straight line, this Using the relationship V _be
The temperature T can be known from.

FIG. 4 shows a second conventional example in which the temperature is measured using two transistors.

And resistor R ₂ and the transistor Q ₃ between the terminals T ₁ and T ₂ are connected in series, further terminals T ₁ and T ₂ resistor to R _3, transistor Q _4, and a resistor R ₄ and a series It is connected to the. The emitter of the transistor Q ₄ has an emitter area twice as large as that of Q ₃ .

The input terminals of operational amplifier Q ₅ , whose power supply terminals are connected to terminals T ₁ and T ₂ , are connected to the collectors of transistors Q ₃ and Q ₄ , respectively, and their output terminals are commonly connected to the bases of transistors Q ₃ and Q _4. It is connected.

The base current is controlled by the operational amplifier Q ₅ so that the collector voltages of the transistors Q ₃ and Q ₄ become equal. Also, the terminal
T _1, the voltage difference ΔV corresponding to the difference between the base / emitter voltage of the transistor of this such as resistor R ₄ due to the difference in emitter area of the flow T ₂ to a current I _t and transistor Q ₃ and Q ₄ are generated . This difference voltage ΔV is not affected by the variation of the current I _t. A change in the temperature of the transistors Q ₃ and Q ₄ causes a change in the difference voltage ΔV, which results in a corresponding change in the current I _t . Therefore, it is possible to measure the temperature T from the change in current I _t.

<Problems to be Solved by the Invention> However, the temperature sensor shown in FIG. 3 is a transistor.
Depending on the shape of Q ₂ or the manufacturing process, the output voltage V _be fluctuates by ± 2%, which is equivalent to ± 6 ° C for a temperature sensor. In the case of the temperature sensor shown in FIG. Is more accurate than that shown in FIG.
Need transistors, these transistors
Q _3, Q due emitter area ratio of ₄ fluctuates ± 1% around the current I _t, which corresponds to a temperature of ± 3 ° C, is difficult to ensure compatibility.

<Means for Solving the Problems> In order to solve the above problems, the present invention uses exp (sin
(T) / 2) A constant current source that generates a constant current that changes into a wave shape and a transistor that measures the temperature are connected between the input terminal and the input terminal. An amplifier is provided, and a sine wave voltage obtained at the previous output terminal is output as a temperature signal corresponding to the previous temperature.

A constant current that changes in the form of an exponential sine is supplied from a constant current source to a transistor inserted in the feedback circuit of the amplifier, and a sine wave AC voltage temperature-modulated by this transistor is obtained from the output end of the amplifier.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

This embodiment is based on an improvement of the conventional temperature sensor shown in FIG.

Therefore, the portions having the same functions as those in the conventional art are designated by the same reference numerals, and the description thereof will be appropriately omitted.

_One end of the inverting input terminal (-) of the operational amplifier Q ₁ has a common potential point.
A constant current source CC that is connected to COM and supplies a constant current I _c (t) that changes in the form of an exponential sine and is expressed by the following equation (3) is connected. The constant current I _c (t) is a transistor. Q ₂
Flowing between the collector and the emitter of. However, I _co is a constant.

I _c (t) = I _co exp [(a · sin (t) + a) / 2a] (3) When this equation (3) is modified, I _c (t) = I _co exp [(sin (t) +1) / 2] = I _co ′ exp [(sin (t) / 2) (3) ′. However, I _co ′ = I _co exp (1/2) is a constant. By substituting this relationship into the equation (2) and taking out the temperature signal V _t , which is its AC component, via the capacitor C connected to the output terminal of the operational amplifier, V _t = ATsin (t) with A as a constant. (4)

The result of simulating the above relationship is shown in FIG.

The horizontal axis represents time, and the vertical axis represents the base-emitter voltage V _be of the transistor Q ₂ and the collector current I _c .

As shown in this figure, the constant current source CC changes to an exponential sine-like constant current I expressed by equation (3).
When flow _c (t), the sinusoidal waveform shown in (4) as a temperature signal V _t Correspondingly been obtained.

<Effects of Device> As described above in detail with the embodiments, according to the present invention, a single transistor is used to remove terms due to the shape of the emitter area and the like. Since the temperature signal is an AC signal, it is easy to amplify even a weak temperature signal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the construction of one embodiment of the present invention, FIG. 2 is a characteristic diagram showing the characteristics of the embodiment shown in FIG. 1, and FIG. 3 is a construction of a conventional first temperature sensor. Circuit diagram, FIG. 4 is a circuit diagram showing a configuration of a conventional second temperature sensor. Q _1, Q ₅ ... operational amplifier, CC ... constant current source, Q _2, ~Q ₄ ... transistor, C ... Capacitor.

Continuation of the front page (56) References JP-A-50-115078 (JP, A) JP-A-51-3683 (JP, A) Practical application Sho-58-49238 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A constant current source that generates a constant current that changes into a wave shape of exp (sin (t) / 2), and this constant current is input to an input end, and a temperature is generated between the input end and the output end. And a transistor to which a transistor for measuring is connected, and outputs a sine-wave voltage obtained at the output end as a temperature signal corresponding to the temperature.