JPH09184768A - Temperature compensation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change a base-emitter voltage while keeping its linearity completely by allowing a collector current wherein the temperature is set as variable to flow in a first transistor. SOLUTION: Transistors(Tr) Q4 and Q5 constitute a first current mirror circuit (A) and transistors TrQ6 to Q9 constitute a second current mirror circuit (B). When the circuit A generates a current Lp , the circuit B also generates the same current. The current Ip is allowed to flow in TrQ11 and Q10 connecting serially with a level shift circuit, and a current IS1 set at a current source S1 is allowed to flow in the TrQ3 of the level shift circuit. The voltage obtained from the Trs Q11 and Q10 are subjected to level shift to the emitter of the TrQ3 , and its voltage is given between the base and emitter of the TrQ2 . The current Ip from the circuit B and current IS2 of the current S2 are allowed to flow at a connection point 2. A collector current IC1 is completely changed according to square characteristic as the temperature is changed. The curve shape of the square characteristic can be adjusted by the current IS2 of the current source S2. The base-emitter voltage VBE1 of the current IC1 and TrQ1 contradicts the changing items according to the square characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating circuit for maintaining linearity of a base-emitter voltage of a bipolar transistor used in a temperature sensor or the like with respect to a temperature change.

[0002]

2. Description of the Related Art The base-emitter voltage of a bipolar transistor varies with temperature and is used for temperature sensors. When it is used for a temperature sensor, it is particularly required to change while maintaining linearity with respect to temperature change. The base-emitter voltage V _BE is represented by the equation (1).

V _BE = {1- (T / T ₀ )} V _G0 + T · V _BE0 / T ₀ + (nkT / q) Ln (T ₀ / T) + (kT / q) Ln (I _C / I _C0 ) (1) Equation (1) is obtained by substituting Equation (3) into Equation (2). V _BE = (kT / q) Ln (I _C / I _S ) (2) I _S = qAn _i ² D _n / Q _B (3)

In the equations (1) to (3), q
Is the electron charge, A is the emitter-base junction area, n _i is the intrinsic carrier concentration of silicon, Q _B is the total amount of impurities per unit area in the base, k is the Boltzmann constant, I _C is the collector current, I _S is Saturation current, T is absolute temperature, T ₀ is reference temperature, V _BE0 and I _C0 are base temperatures at reference temperature T ₀ .
The emitter-to-emitter voltage and collector current, V _G0 is an estimated value of the silicon bandgap voltage, n is a constant, and Ln is a symbol of natural logarithm. In the formulas below, the same symbols represent the same meaning. In the equation (1), the first two terms change while maintaining linearity with respect to the temperature change, while the third term changes due to the square characteristic. FIG. 3 is a diagram showing changes in the value of the third term,
The horizontal axis represents the absolute temperature T, and the vertical axis represents the value f (T) of the third term. Since f (T) is expressed by equation (4), the coefficient of the squared term is negative. f (T) = (nk / q) Ln (T ₀ ) .T- (nk / q) Ln (T) .T (4) Therefore, by canceling the change according to the square characteristic, the straight line of the voltage change is obtained. Sexuality is maintained.

FIG. 2 shows a circuit diagram of a conventional temperature compensation circuit. This circuit is formed so that the base-emitter voltage of the diode-connected first transistor Q1 changes linearly with respect to temperature changes. The power supply voltage V _CC causes the current source S3 to generate a current proportional to the absolute temperature, and this current flows through the diode-connected transistors Q21 and Q20. Transistor Q22,
The base of Q23 is connected to the collectors of transistors Q21 and Q20, respectively. A transistor Q23 having N multi-emitters and resistors R21 and R20 set the collector current of the transistor Q22 connected to the emitter of the transistor Q1. The collector of the transistor Q24 is
It is connected to the emitter of the transistor Q1.

The current of the current source S3 is I _S3 , and the transistor Q
21 collector current and base-emitter voltage are respectively I
_C21 , V _BE21 , collector current and base-emitter voltage of transistor Q20 are I _C20 , V _BE20 , collector current of transistor Q22 and base-emitter voltage are I _C22 , V _BE22 , collector current and base of transistor Q24, respectively. _-Equations (5), (6), and (7) hold when the emitter-to-emitter voltages are I _C24 and V _BE24 , respectively.

[0007] _{V BE24 = Ln (I C24 /} I S) (5) V BE24 = V BE20 + V BE21 -V BE22 (6) I C24 = I C20 · I C21 / I C22 = I S3 2 / I C22 (7 )

The current I _S3 has a positive temperature coefficient,
By fixing the current I _C22 , the current I _C24 changes according to the square characteristic with respect to the temperature change. The coefficient of the squared term is positive. Current _IC24 and base of transistor Q1
The emitter-to-emitter voltage V _BE1 is V _BE and I _C in the equation (2).
Since V _BE1 and I _C24 are replaced by each other, this current I _C24 changes according to the square characteristic of the equation (1),
That is, the third term is canceled out, and the voltage V _BE1 is used so as to change while maintaining linearity with respect to temperature changes. 4th
The term is small and can be ignored. However, the current I _S3 of the current source S3 generally forms a current mirror circuit with a pair of transistors having different current densities, and the base-emitter voltage difference is applied to both ends of the resistor to generate a current. Therefore, the current I _S3 is expressed by the equation (8).

I _S3 = {k (t + 273) / qR} · Ln (N) (8) where t is the temperature (° C), R is the resistance value of the resistor, and N is the difference in current density, which is the transistor on one side. Shows that the current density is 1 / N compared to the rest of the transistors.
Equation (8) is expressed as a linear expression of temperature, that is, in the form of (at + b). When squared, the second-order term of temperature and the second-order term of (2abt) appear. It does not change. Therefore, the linearity of the voltage V _BE1 is still difficult to maintain.

[0010]

The problem to be solved by the present invention is as follows.
_Another object of the present invention is to provide a temperature compensation circuit in which the base-emitter voltage V _BE1 of the transistor of FIG.

[0011]

According to the present invention, in a temperature compensation circuit for a base-emitter voltage of a first transistor, a first current mirror circuit, a second current mirror circuit, a level shift circuit, a first current mirror circuit, and a first current mirror circuit. A second current source, a second transistor, a first current mirror circuit comprising a pair of transistors including a one-sided transistor with multiple emitters, and a second current mirror circuit comprising a first current mirror circuit of the first current mirror circuit. The level shift circuit is connected as a load, and each of the level shift circuits is diode-connected and connected in series, and another pair of transistors through which the current of the second current mirror circuit flows,
It comprises a third transistor having a first current source connected to the emitter thereof and level-shifting the voltage obtained by the other pair of transistors to the emitter thereof, the second transistor being connected in series with the first transistor and having a base. Is applied with a level-shifted voltage, and the connection point between the first and second transistors is characterized in that the second current mirror circuit and the second current source are connected.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The temperature compensating circuit of the present invention is configured such that a collector current including a quadratic term and a primary term in which a temperature is a variable is passed through a first transistor, and the base-emitter voltage squared. It is possible to cancel the term that changes depending on the characteristic so that the base-emitter voltage changes while maintaining the linearity completely.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the temperature compensation circuit of the present invention will be described below with reference to FIG. In FIG. 1, a transistor Q4 having N multi-emitters and a transistor Q5 form a first current mirror circuit, the emitter of the transistor Q5 is directly grounded, and the transistor Q4
The emitter of is grounded via a resistor R1. Then, the first current mirror circuit functions as a current source circuit for flowing the current I _P shown by the expression (9). I _P = {k (273 + t) / qR1} Ln (N) (9) Note that R1 represents the resistance value of the resistor R1.

Transistors Q6, Q7, Q8, Q9 form a second current mirror circuit, and transistor Q
6, Q7 are directly connected as the active load of the first current mirror circuit. Each emitter of the transistors of the second current mirror circuit is connected to the terminal 1 to which the power supply voltage V _CC is applied. Transistors Q11, Q10 and a third transistor Q, which are diode-connected to each other and are connected in series
3. The first current source S1 forms a level shift circuit.

The collector of the transistor Q11 is connected to the collector of the transistor Q8 and the base of the transistor Q3. The collector of the transistor Q3 is connected to the terminal 1, and the emitter is grounded via the first current source S1. The first diode-connected transistor Q1 is connected in series with the second transistor Q2, the collector of which is connected to the terminal 1 and the emitter of which is connected to the collector of the transistor Q2. The emitter of the transistor Q2 is grounded. The collector of the transistor Q9 of the second current mirror circuit and the second current source S2 are connected to the connection point 2 between the transistor Q1 and the transistor Q2.

The temperature compensating circuit thus configured maintains the linearity with respect to the temperature change of the base-emitter voltage of the first transistor Q1. The operation will be described below. The first current mirror circuit produces the current I _P shown in equation (8), and the same current also flows in the second current mirror circuit. This current I _P flows through the transistors Q11 and Q10 connected in series in the level shift circuit. In addition, the transistor Q3 of the level shift circuit has a first current source S
The current I _S1 set at 1 flows.

The voltage obtained by the transistors Q11 and Q10 is level-shifted to the emitter of the transistor Q3, and the level-shifted voltage is applied to the base of the transistor Q2. The base-emitter voltage V _BE2 of the transistor Q2 is obtained by the equation (10). _{V BE2 = V BE10 + V BE11} -V BE3 (10) V BE10, V BE11, V BE3 are each transistor Q10, Q
11, Q3 is the base-emitter voltage.

Since the relationship between the base-emitter voltage and the collector current of each transistor is expressed by the equation (2), the collector current I _C2 of the transistor Q2 is expressed by the equation (11). I _C2 = I _C10 · I _C11 / I _S1 = I _P ² / I _S1 (11) I _C10 and I _C11 are collector currents of the transistors Q10 and Q11, respectively. A current I _P and a current I _{S2 of} the second current source S2 flow from the second current mirror circuit to the connection point 2.

Therefore, the collector current I _C1 of the first transistor Q1 is expressed by the equation (12). I _C1 = {(I _P ² / I _S1 ) −I _P + I _S2 } (12) If the current I _P is expressed by the linear expression (at + b), the expression (13) is obtained from the expression (12). ^{_{I C1 = {(at) 2}} + 2abt + b 2 -I S1 (at + b) + I S1 I S2} / I S1 = {(at) 2 + (2ab-a I S1) t -I S1 b + b 2 + I S1 I S2} / I _S1 (13) The first term of the temperature in the numerator of the equation (13), that is, (2
ab−a I _S1 ) t can be eliminated by setting the current I _S1 . The coefficient of the squared term is positive.

Therefore, the collector current I _C1 changes completely according to the temperature change due to the square characteristic. In this case, the temperature coefficient of the current I _P is positive, it may be either negative. FIG.
It is a figure which shows the change of electric current I _C1 , and the horizontal axis represents absolute temperature T. The shape of the curve of the squared characteristic can be adjusted by the current I _S2 of the current source S2. This collector current I _C1 and the base-emitter voltage V of the transistor Q1
_BE1 is, (2) V _BE, husband I _C s V _BE1 in formula, I
_Since it has a relationship of being replaced with _C1 , it is possible to cancel the term that changes according to the square characteristic of equation (1). Then, the voltage V _BE1 can be changed while maintaining the linearity with respect to the temperature change. In Figure 5, the voltage V _BE1 is (2 mV / °
Is a diagram showing changes in the voltage V ₁ of the difference between the theoretical value and the measured value of the voltage V _BE1 of the case of varying temperature coefficient of C). -40 °
In the wide range from C to 120 ° C, the difference is within ± 1 mV, and it is clear that the linearity of the voltage V _BE1 is maintained. Although the base-emitter voltage of one transistor has been described in the embodiment, a more accurate reference voltage can be obtained by forming a bandgap reference voltage generation circuit using such a temperature-compensated transistor. it can. Further, in the embodiment, the first transistor is diode-connected, but the connection is not limited to this.

[0021]

As described above, the temperature compensating circuit of the present invention can change the base-emitter voltage of the bipolar transistor with respect to temperature changes while maintaining linearity. Therefore, if the transistor is used for a temperature sensor, an accurate temperature can be measured, and if it is used for a reference voltage generation circuit, an accurate reference voltage can be obtained.
It is an extremely practical invention.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a temperature compensation circuit of the present invention.

FIG. 2 is a circuit diagram of a conventional temperature compensation circuit.

FIG. 3 is a diagram showing states of terms that change depending on a square characteristic of a base-emitter voltage of a transistor.

FIG. 4 is a first component compensated by the temperature compensation circuit of the present invention.
6 is a diagram showing how the collector current of the transistor of FIG.

FIG. 5 is a first component compensated by the temperature compensation circuit of the present invention.
FIG. 6 is a diagram showing a voltage of a difference between a measured value and a theoretical value of a base-emitter voltage of the transistor of FIG.

[Explanation of symbols]

 Q1 first transistor Q2 second transistor S1 first current source S2 second current source

Claims (1)

[Claims] 1. A temperature compensation circuit for a base-emitter voltage of a first transistor, comprising: a first current mirror circuit, a second current mirror circuit, a level shift circuit, a first and a second current source, and a second current mirror circuit. The first current mirror circuit is composed of a pair of transistors including the one-sided transistor having multiple emitters, and the second current mirror circuit is connected as a load of the first current mirror circuit. The shift circuit is obtained by another pair of transistors, each of which is diode-connected and series-connected, and through which the current of the second current mirror circuit flows, and a first current source connected to the emitter of the pair of transistors. A third transistor for level shifting the applied voltage, the second transistor being connected in series with the first transistor and having a base A temperature-compensated circuit in which a voltage level-shifted is applied to, and a connection point between the first and second transistors is connected to a second current mirror circuit and a second current source.