JP3138203B2 - Reference voltage generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference voltage generating circuit capable of obtaining an accurate bandgap voltage without being affected by a change in temperature.

[0002]

2. Description of the Related Art A bandgap voltage is used as a reference voltage because it is hardly affected by a change in temperature. FIG. 2 is a circuit diagram of a known band gap reference circuit (hereinafter, referred to as a BG circuit), and includes transistors Q3, Q4, and Q6.
Further, it is formed of a transistor Q5 having a multi-emitter, a resistor R1, and a resistor R2. 8 is the power supply voltage V _CC
A power supply terminal 7 is an output terminal. If the collector current I ₆ of the collector current I ₅ and the transistor Q6 of the transistor Q5 is equal, is obtained from a bandgap voltage V _G is terminal 7 shown in (1). _{V G = 2I 5 · R2 +} V BE6 = {2R2 · V T · Ln (N) / R1} + V BE6 (1)

[0003] However, R1 and R2 is the resistance value of the resistor and each resistor R1 R2, V _BE6 the base-emitter voltage of the transistor Q6, V _T is the thermal voltage, Ln is the natural logarithm symbol,
N is the number of emitters of transistor Q5. Thermal voltage V
Temperature coefficient of _T is positive in (0.085mV / ° C), since the temperature coefficient of the base-emitter voltage V _BE6 is negative extent (-2mV / ° C), ( 1) the resistance value in the equation R1, R2 Is appropriately selected so that the band gap voltage V _G without the influence of the temperature change
Is obtained. However, precisely band gap voltage V _G when measured has received still the influence of the temperature change.

This is because the base-emitter voltage V _BE of the bipolar transistor is expressed by the following equation (2). _{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) ( 2) Equation (2) is obtained by substituting equation (4) into equation (3). _{V BE = (kT / q)} Ln (I C / I S) (3) I S = qAn i 2 D n / Q B (4) Here, in equation (4) from equation (2), q is the electronic charge, a is the emitter-base junction area, n _i is the intrinsic carrier concentration of silicon, D _n is the average effective value of the electron diffusion coefficient in the base, Q _B is the total amount of impurities per unit area in the base, k is Boltzmann constant, I _C is collector current, I _S
Is the saturation current, T is the absolute temperature, T ₀ is the reference temperature, V _BE0 and I _C0 are the base-emitter voltage and collector current at the reference temperature T ₀ , VG ₀ is the estimated value of the silicon band gap voltage, and n is a constant It is.

In equation (2), the first two terms change while maintaining a straight line with respect to the temperature change, while the third term changes due to the square characteristic. FIG. 3 is a diagram showing a change 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 represented by equation (5), the coefficient of the square term is negative. f (T) = (nk / q) Ln (T 0) · T- properties of (nk / q) Ln (T ) · T (5) such a base-emitter voltage V _BE is a bandgap voltage It is apparent that the same occurs in the obtained base-emitter voltage V _BE6 of the transistor Q6. Then, does not change linearly with the temperature coefficient of exactly due to the presence of the voltage V _BE6 is the square of the term (-2mV / ° C), the band gap voltage V _G can not be avoided still the influence of temperature change. The value of the fourth term in the equation (2) is small and can be ignored.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a bandgap voltage of a BG circuit from a base of a transistor in which a base-emitter voltage changes while maintaining linearity, and completely eliminate the influence of a temperature change. An object of the present invention is to provide a reference voltage generating circuit which can be eliminated.

[0007]

A reference voltage generating circuit according to the present invention comprises a first, second, third, and fourth current mirror circuits, a level shift circuit, first and second current sources, and first and second current sources. The first transistor comprises a second transistor and a BG circuit, the first current mirror circuit comprises a pair of transistors including one transistor provided with a multi-emitter, and the second current mirror circuit comprises a first transistor.
The level shift circuit is diode-connected and connected in series, and another pair of transistors through which the current of the second current mirror circuit flows, and a first current source as an emitter. A third transistor connected to the emitter for level-shifting the voltage obtained by the other pair of transistors,
Transistor is connected to the second current mirror circuit, the third current mirror circuit, the second current source, and the level-shifted voltage is applied to the base, and the third current mirror circuit is connected to the fourth current mirror circuit. The first transistor is connected between the third current mirror circuit and the fourth current mirror circuit, and the transistor for obtaining the bandgap voltage of the BG circuit and the emitter are connected in common; A band gap voltage can be obtained from a base of the transistor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS By flowing a collector current including a quadratic term whose temperature is a variable to a first transistor,
The term which varies according to the square characteristic of the base-emitter voltage is canceled, and the first transistor and the emitter of the transistor for obtaining the bandgap voltage of the BG circuit are connected in common, and the bandgap voltage is referenced from the base of the first transistor. It is obtained as a voltage.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reference voltage generating circuit according to the present invention will be described below with reference to FIG. The same parts as those in FIG. 2 are denoted by the same reference numerals. In FIG. 1, a transistor Q16 having M multi-emitters and a transistor Q17 form a first current mirror circuit 1, an emitter of the transistor Q16 is grounded via a resistor R3, and an emitter of the transistor Q17 on the bias side is directly grounded. Is done. The transistors Q12, Q13, Q14, and Q15 form a second current mirror circuit 2, and are connected as a load of the first current mirror circuit 1. The collector of the transistor 14 on the bias side is the collector of the transistor 16, and the collector of the transistor Q15 is the transistor Q.
17 and the emitter of each transistor is connected to the power supply terminal 8.

The third transistor Q18, transistors Q19 and Q20 form a level shift circuit 5,
Transistors Q19 and Q2 which are respectively diode-connected
0 is connected in series, and the collector of the transistor Q19 is connected to the second
And the emitter of the transistor Q20 is grounded.
The collector of the third transistor Q18 is connected to the terminal 8, and the emitter is grounded via the first current source S1. The collector of the second transistor Q2 is the transistor Q12.
And the collector of the transistor Q9, the second current source S2, the base is connected to the emitter of the third transistor Q18, and the emitter is grounded.

The transistors Q7, Q8, and Q9 form a third current mirror circuit 3, and include a transistor 9 on the bias side.
Are grounded via a second current source S2, and the emitter of each transistor is connected to terminal 8. The transistor Q10 and the transistor Q11 form a fourth current mirror circuit 4, and the emitter of each transistor is grounded. The third current mirror circuit 3 is connected as a load of the fourth current mirror circuit 4, and the collector of the transistor Q7 is connected to the collector of the transistor Q10 via the diode-connected first transistor Q1.
8 is connected to the collector of transistor Q11.

The transistors Q3, Q4, Q5 and Q6, the resistors R1 and R2 form a BG circuit 6, and a multi-emitter transistor Q5 having N emitters
And the base of the transistor Q6 is connected. The emitter of the transistor Q5 is grounded via the resistors R1 and R2, and the connection point between the resistors R1 and R2 is connected to the emitter of the transistor Q6. The collectors of the transistors Q6 and Q4 on the bias side and the collectors of the transistors Q3 and Q5 are connected, and the emitters of the transistors Q3 and Q4 are connected to the power supply terminal 8. Then, the emitter of the transistor Q6 for obtaining the bandgap voltage of the BG circuit 6 and the emitter of the first transistor Q1 are connected to each other, and a bandgap voltage is obtained from the output terminal 7 connected to the collector of the transistor Q1.

In the reference voltage generating circuit thus configured, the fourth current mirror circuit 4 prevents the current flowing through the first transistor Q1 from flowing into the BG circuit 6. The first current mirror circuit 1 which serves as a current source circuit for supplying a current I _P represented by equation (6). In addition,
T in the equation (6) represents a temperature. I _P = ｛k (273 + t) / q · R1｝ Ln (M) (6) This current I _P also flows through the second current mirror circuit 2, and the transistor Q19, which is connected in series with the level shift circuit 5,
It also flows in Q20.

The voltages obtained by the transistors Q19 and Q20 are level-shifted to the emitter of the third transistor Q18, and the level-shifted voltage is applied to the base of the second transistor Q2. The base-emitter voltage V _BE2 of the transistor Q2 is expressed by equation (7). _{V BE2 = V BE20 + V BE19} -V BE18 (7) V BE18, V BE19, V BE20 are each transistor Q18, Q
19 and Q20 are the base-emitter voltages.

The relationship between the base-emitter voltage and the collector current of each transistor is expressed by equation (3).
The collector current I _C2 of the transistor Q2 is expressed by equation (8). _{I C2 = I C20 · I C19} / I S1 = I P 2 / I S1 (8) I C20, I C19 are each transistors Q20, Q19 of the collector current, I _S1 is the current of the current source S1. Since the collector of the second transistor Q2 is connected to the second current mirror circuit 2, the second current source S2, and the third current mirror circuit 3, the current expressed by the equation (9) is applied to the connection point 9. Flows, and this current is equal to the current flowing through the third current mirror circuit 3. This current is equal to the collector current I _C1 of the first transistor Q1. I _C1 = {(I _P ² / I _S1 ) −I _P + I _S2 } (9) I _S2 is the current of the second current source S2.

Since the current I _P represented by the equation (6) is a linear equation with the temperature t as a variable, it is represented as (at + b). The expression (10) is obtained from the expression (9). ^{_{I C1 = {(at) 2}} + 2abt + b 2 -I S1 (at + b) + I S1 I S2} / I S1 = {(at) 2 + (2ab-aI S1) t-I S1 b + b 2 + I S1 I S2} / I _S1 (10) The first-order term of the temperature in equation (10), that is, (2ab-aI _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 of the transistor Q1 changes completely with the square characteristic with respect to the temperature change. The temperature coefficient of the current I _P is positive, it may be either negative. FIG. 4 is a diagram showing a change in the current I _C1 , and the horizontal axis represents the absolute temperature T. The shape of the squared characteristic curve can be adjusted by the current I _S2 of the current source S2. The collector current I _C1 and the base-emitter voltage V _BE1 of the transistor Q1 are obtained by _dividing V _BE and I _C in the equation (3) by V _BE1 and I _BE
Since the relationship is replaced by _C1 , the term whose square changes according to the square characteristic of the base-emitter voltage V _BE1 expressed by the equation (2) is canceled by flowing the collector current I _C1 having a positive coefficient. be able to. And the voltage V
_BE1 can be changed while maintaining linearity with respect to temperature change. The bandgap voltage V _G obtained from the output terminal 7 is expressed by equation (11). V _G = 2I ₅ · R 2 + V _BE1 = {2R 2 · V _T · Ln (N) / R 1} + V _BE1 (11) As the voltage V _BE1 changes while maintaining linearity, the temperature to the bandgap voltage V _G is obtained. The effects of change can be completely eliminated.

FIG. 5 shows the reference voltage generating circuit of the present invention and FIG.
FIG. 7 is a diagram showing a state of a change in a band gap voltage with respect to temperature in the conventional BG circuit of FIG. However, the difference between the theoretical value and the measured value when the base-emitter voltage of the transistor that finally obtains the band gap voltage changes at (−2 mV / ° C.) is shown. The solid line is the difference between the measured value of the bandgap voltage of the circuit of the present invention and the theoretical value when the temperature coefficient of the base-emitter voltage V _BE1 in equation (11) is (−2 mV / ° C.). The dotted line is the difference between the theoretical value when measured values of the band gap voltage of the circuit of FIG. 2 and (1) the temperature coefficient of the base-emitter voltage V _BE6 of the equation (-2 mV / ° C). According to the present invention, -40 ° C to 120 ° C
It can be seen that the difference from the theoretical value is within ± 1 mV over a wide range, and that the linearity of the voltage V _BE1 is maintained.

[0019]

As described above, the reference voltage generating circuit according to the present invention maintains the linearity of the base-emitter voltage of the transistor for obtaining the bandgap voltage, thereby preventing the influence of the temperature change on the accurate band. It is an invention that can obtain a gap voltage as a reference voltage and is extremely practical when a precise reference voltage is required.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a reference voltage generation circuit according to the present invention.

FIG. 2 is a circuit diagram of a conventional BG circuit.

FIG. 3 is a diagram illustrating a state of a term that changes according to a square characteristic of a base-emitter voltage of a transistor.

FIG. 4 is a diagram showing a change in a collector current of a first transistor of the reference voltage generation circuit of the present invention.

FIG. 5 is a diagram showing how the bandgap voltage of the reference voltage generation circuit of the present invention and the conventional BG circuit changes with temperature.

[Explanation of symbols]

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

Claims (1)

(57) [Claims] A first current mirror circuit, a level shift circuit, first and second current sources, first and second transistors, and a band gap reference circuit; One current mirror circuit includes a pair of transistors including one transistor having a multi-emitter, the second current mirror circuit is connected as a load of the first current mirror circuit, and the level shift circuit is diode-connected. And another pair of transistors connected in series and through which the current of the second current mirror circuit flows, and the voltage obtained by the other pair of transistors is level-shifted to its emitter and connected to the first current source. And a second transistor connected to a second current mirror circuit, a third current mirror circuit, a second current source, and having the base connected to the level mirror. A third current mirror circuit is connected as a load of the fourth current mirror circuit, the first transistor is connected between the third current mirror circuit and the fourth current mirror circuit, A reference voltage generating circuit, wherein a transistor for obtaining a bandgap voltage of a bandgap reference circuit and an emitter are commonly connected, and a bandgap voltage is obtained from the first transistor.