JPH0561656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reference voltage generator suitable for integrated circuits.

[Technical background of the invention and its problems]

Conventionally, a reference voltage generator called a band gear reference has been frequently used in integrated circuits.

Figure 1 shows the basic configuration of such a conventional reference voltage generator, where 1 is a current source, 2 is a diode-connected transistor, 3 is an adder, and 4 is a voltage generator proportional to absolute temperature. and the output generated at the collector of transistor 2 and the voltage generator 4
The adder 3 adds the output to the output terminal 5 and outputs the result to the output terminal 5. In such a reference voltage generator, the relationship between the collector current Ic of the transistor 2 and the base-emitter voltage _VBE is given by the following equation.

Ic≒Isexp( _qVBE /kT)...(1) Here, Is is the saturation current, q is the electronic charge, k is Boltzmann's constant, and T is the absolute temperature.

Further, it is known that the saturation current Is is as follows: _Is = _Isp ·T ^P ·exp(−qV _G /kT) (2). Here, I _sp is a saturation current constant, P is a constant, and V _G is a forbidden voltage of a semiconductor constituting a transistor, and has a constant value. Transforming equation (1), we get V _BE =kT/qln(Ic/Is)...(3). Substituting equation (2) into this, we get V _BE =kT/q[lnI _c −lnI _sp −PlnT]+V _G …(4).

On the other hand, the output voltage V _O generated at the output terminal 5 is given by V _O =V _BE +C·kT/q (5). Here C is a constant. Therefore, by substituting the above equation (4) into this equation (5), the following equation holds true.

V _O =V _G +kT/qlnIc-lnIso-PlnT+C]...(6) In equation (6), by appropriately selecting C, the temperature coefficient of the output voltage V _O can be set to 0 at a certain temperature. However, in reality, as is clear from equation (6), no matter how the value of C is selected, the temperature coefficient of the output voltage cannot be made zero over a wide temperature range.

FIG. 2 shows the temperature characteristics of a conventional reference voltage generator, which always changes with temperature.

[Purpose of the invention]

An object of the present invention is to improve the drawbacks of conventional reference voltage generators and to provide a reference voltage generator whose output voltage is constant regardless of temperature.

[Summary of the Invention] This invention provides a second voltage generator for correction in a conventional reference voltage generator, and corrects the reference voltage using a voltage proportional to the voltage difference between the outputs thereof. be.

[Embodiments of the invention]

The present invention will be explained in detail below with reference to the drawings.

FIG. 3 shows the basic configuration of the reference voltage generator of the present invention. In the figure, 11 is a current source that supplies a current proportional to the power of the absolute temperature to the collector of the transistor 12. transistor 1
2 is a so-called diode-connected transistor whose emitter is grounded and whose base and collector are commonly grounded. The base-emitter voltage V _BE that is the output of this transistor 12 is supplied to an adder circuit 13 . The adder circuit 13 is supplied with output voltages from a voltage generator 14 which generates a voltage proportional to absolute temperature and a generator 16 which generates a voltage proportional to the product of absolute temperature and the logarithm of absolute temperature. These three voltages are then added together,
The added voltage V _ON is obtained at the output terminal 15.

Next, the principle of operation of this reference voltage generator will be explained.

In the reference voltage generator according to the present invention, the output voltage
V _ON is V _ON = V _BE +D・kT/q+E・kT/qln(kT/q/Vr)…
(7). Here, D and E are constants, and Vr is a suitable voltage. Substituting equation (4) into equation (7), V _ON =V _G +kT/q[lnIc−lnIso+D]+kT/q[Eln(k
T/q/Vr)−PlnT]...(8) Assuming that the temperature characteristic of collector current Ic is Ic=G・^TQ ...(9), equation (8) can be summarized as the following equation.

V _ON =V _G +kT/q(D+Elnk/q/V _r +lnG/I _SO )+k
T/q(E+Q-P)・lnT...(10) Here, if E=P-Q D=Eln(qVr/k)-ln(Iso/G) (12), the output voltage V _ON becomes V _G , which is a constant voltage regardless of the temperature.

Here, the constants P and Iso are determined by the transistor manufacturing conditions, and therefore, it is easy to determine E and D. Furthermore, appropriate voltage Vr
can be obtained from the output voltage V _ON .

As described above, according to the present invention, a constant voltage can always be generated regardless of temperature by configuring a circuit using coefficients E and D determined from constants determined in advance from semiconductor manufacturing conditions.

FIG. 4 shows a specific embodiment of the present invention. This embodiment includes two current sources 11 and 18 having different dependencies on absolute temperature, two transistors 12 and 19 respectively connected to them, and a voltage generator 14 that generates a voltage proportional to absolute temperature. It is composed of a voltage adder 13.

It is assumed that the temperature characteristics of the current values I _C1 and I _C2 of the current sources 11 and 18 are given by the following equations, respectively.

I _c1 = G ₁ T ^Q1 …(13) I _C2 = G ₂ T ^Q2 …(14) At this time, the bases of transistors 12 and 19
The emitter-to-emitter voltages V _BE1 and V _BE2 are obtained from equation (4) as follows.

V _BE1 = kT/q(lnG ₁ +Q ₁ lnT−lnIso ₁ −PlnT)+V _G …(15) V _BE2 =kT/q(lnG ₂ +Q ₂ lnT−lnIso ₂ −PlnT)+V _G …(16) Here , Iso ₁ and Iso ₂ are transistor 1, respectively.
The saturation current constant is 2.19. Voltage adder 13
When the addition coefficients for V _BE1 , V _BE2 , and kT/q are (1+k), (-k), and F, respectively, the output voltage V _ON is given by the following equation.

V _ON =(1+k)V _BE1 −KV _BE2 +F・kT/q=V _BE1 +K(
V _BE1 −V _BE2 )+F・kT/q…(17) Substituting equations (15) and (16) into this equation, V _ON =kT/q(lnG ₁ +Q ₁ lnT−lnIso ₁ −PlnT) ＋V _G ＋KkT
/q [ln(G ₁ /G ₂・Iso ₂ /Iso ₁ ) + (Q ₁ − Q ₂ ) lnT] +
F・kT/q = V _G +kT/q [lnG ₁ /Iso ₁ +Kln(G ₁ /G ₂・Iso ₂ /I
so ₁ )+F]+kT/q[K(Q ₁ −Q ₂ )+Q ₁ −P]lnT…(1
8) becomes. Here, regarding the addition coefficient of the voltage adder, K=P−Q ₁ /Q ₁ −Q ₂ …(19) F=ln [(Iso ₁ /G ₁ ) ^K+1 −(G ₂ /Iso ₂ ) ^K ] ...(20) Then, the output voltage V _ON becomes a constant voltage V _G regardless of the temperature.

In this embodiment, the third term in equation (7), which is proportional to the product of the absolute temperature and the logarithm of the absolute temperature, is used as the base-emitter of a transistor driven by two current sources with different temperature characteristics. It is characterized by being generated from the voltage difference between the two voltages.

In this embodiment, the voltage proportional to the absolute temperature can be generated by a known circuit that utilizes the fact that the difference between the base-emitter voltages of two transistors with a constant current ratio is proportional to the absolute temperature. In addition, in order to create a current with temperature dependence as shown in equations (13) and (14), it is necessary to apply a voltage proportional to the power of the absolute temperature, for example, the voltage proportional to the absolute temperature mentioned above, whose temperature dependence is , which can be easily realized by applying it to a resistance proportional to the power of the absolute temperature.

FIG. 5 shows another embodiment of the invention. In this embodiment, the second current source 18 in the previous embodiment is replaced with a voltage-current converter 20 that generates a current proportional to the output voltage. In this case, Q ₂ in equation (14) becomes 0, but equation (18) holds true as is, and as described above, the output voltage becomes a constant value V _G regardless of the temperature. The features of this embodiment are as follows:
The point is to obtain a constant current regardless of temperature from a constant voltage regardless of temperature, which is the output.

FIG. 6 shows another embodiment of the invention. In this embodiment, transistors 21, 22, resistors 26, 27,
28, 29 and an operational amplifier 35; a voltage adder consisting of resistors 30, 31 and an operational amplifier 36; a transistor 23 and a resistor 3;
2, 33, 34 and an operational amplifier 37. First, the output voltages of the two voltage generators are determined, and then the overall operation will be explained.

First, find the output voltage of one voltage generator.

Let collector currents of transistors 21 and 22 be Ic ₁ and Ic ₂ , respectively, and resistance values of resistors 26 and 27 be R26 and R27, respectively. Assuming for simplicity that the saturation currents of the transistors 21 and 22 are equal, the voltage Δvbe generated across the resistor 28 is Δvbe=kT/qlnIc ₂ / _Ic 1 (21). Since the voltages across the resistors 26 and 27 become equal due to the negative feedback effect of the operational amplifier 35, Ic ₁ R26=Ic ₂ R27 (22) holds true. Therefore, equation (21) becomes as follows.

△vbe=kT/qlnR26/R27...(23) Assuming that the current amplification factors of the transistors 21 and 22 are sufficiently large, the current flowing through the resistor 28 is △vbe/
R28 is approximately equal to Ic ₁ . That is, Ic ₁ =1/R28 kT/qlnR26/R27 (24). Here, R28 is the resistance value of the resistor 28.
Also, using equation (22), Ic ₂ =R26/R27 R28 kT/qlnR26/R27...(25). Since the current flowing through the resistor 29 is the sum of Ic ₁ and Ic ₂ , the voltage V29 generated across the resistor 29 is
is, V29=R29/R28 (R26+R27/R27)kT/qlnR26/R27…(2
6) becomes. Here, R29 is the resistance value of the resistor 29.

If we define A=R29/R28(R26+R27/R27)lnR26/R27...(27), we can write V29=A・kT/q...(28). Assuming that the base-emitter voltage of the transistor 22 is V _BE22 , the output voltage Vo ₁ appearing at point 39 is given by the following equation.

Vo ₁ = V _BE22 +AkT/q...(29) If the saturation current constant of transistor 22 is Iso ₂ , then from equation (4), V _BE22 = kT/q(lnIc ₂ -lnIso ₂ -PlnT) +V _G ...(30 ). Ic ₂ is given by equation (25), and the absolute temperature T
Therefore, if G is the proportionality coefficient, Ic ₂ =GT...(31), where G=R26/R27R28lnR26/R27 k/q...(32). To summarize the above, equation (29) becomes as follows.

Vo ₁ =V _G +kT/q(lnGT-lnIso ₂ -PlnT+A)...(33) Next, find the output voltage of the other voltage generator. The resistance values of resistors 32, 33, and 34 are R
32, R33, and R34. The output voltage of the entire device appears at point 41, and as described later,
Since its value is V _G , the collector current Ic ₃ flowing through the transistor 3 is expressed by the following equation, and is constant regardless of temperature as long as the temperature coefficient of resistance is negligibly small.

Ic ₃ = V _G /R32・R33/R33+R34 (34) Therefore, the output voltage Vo ₂ appearing at point 30 is equal to the base-emitter voltage of transistor 23, and if the saturation current constant of transistor 23 is Iso ₃ , then , from equation (4), Vo ₂ =V _G +kT/q(lnIc ₃ −lnIso ₃ −PlnT) …(35).

The resistance values of resistors 30 and 31 are R30 and R31, respectively.
Then, the resistance ratio is K=R31/R30...(36) Then, the voltage adder calculates the voltage appearing at point 39.
Vo ₁ and the voltage Vo ₂ represented by point 30 are input, and an output voltage Vo ₃ of the entire device as represented by the following equation is generated.

Vo ₃ =Vo ₁ +K(Vo ₁ −Vo ₂ ) (37) For simplicity, if Iso ₂ =Iso ₃ =Iso, the above equation is expanded as follows.

Vo ₃ =V _G +kT/q(lnGT-lnIso-PlnT+A)+KkT/q
(A+lnGT-lnI _C3 ) =V _G +kT/q{(1+K)A+ln(G ^K+1 /Iso・Ic ₃ K
)}+kT/q(K+1-P)lnT...(38) Therefore, adjust the circuit constants A and K determined by equations (27) and (36) as shown in equations (39) and (40). Therefore, the output voltage Vo ₃ can be kept at a constant value V _G regardless of the temperature.

K=P-1...(39) A=1/1+k[ln(I _sp・I _C3・K/G ^K+1 )]...(40) Figure 7 shows another embodiment of the present invention. It is. As in the previous embodiment, voltages given by equations (33) and (35) are generated at points 39 and 40, respectively. Therefore, a current I ₁₀ given by the following equation flows through the resistor 30.

I ₁₀ = 1/R ₃₀ (Vo ₁ −Vo ₂ )...(41) If the base currents of transistors 21 and 22 are negligibly small compared to this current, a current approximately equal to this current flows through resistor 31. Therefore, the output voltage Vo ₃ appearing at point 41 is
It is given by the same formula as (38). The feature of this embodiment is that one voltage generator also has a voltage addition function.

FIG. 8 shows an embodiment in which the embodiment shown in FIG. 7 is constructed using transistors instead of the operational amplifiers.

Transistors 54, 55, 56, 57, 58,
59 and constant current sources 82 and 83 constitute an operational amplifier, and together with resistors 70, 71, 72, 73 and transistors 21 and 22, generate a voltage Vo ₁ given at point 87 by equation (33). Transistor 61,6
2, 63, 64, 65, 66 and constant current source 84,
85 constitutes another operational amplifier, and resistor 7
9, 80, 81, and the transistor 60, a voltage Vo ₂ given by equation (35) is generated at a point 88. The output voltage Vo ₃ of the entire device appears at point 89 and is given by equation (38) as in the previous embodiment.

Resistor 75 and transistors 67, 68, and 69 determine the base potential of transistor 53. Since the base-emitter voltage of transistor 67 is approximately equal to the base-emitter voltage of transistor 59, the collector currents of transistors 67 and 68 depend on Vo ₃ (=V _G ) and resistor 74 and are independent of temperature. It is almost constant. ((However, it is assumed that the current amplification factors of transistors 67 and 68 are sufficiently high.) Since the base-emitter voltages of transistors 68 and 69 are the same, the resistor 7
A current determined by the saturation current ratio of transistors 18 and 19 flows through transistor 5. One end of the resistor 75 is connected to a point 89, and its potential is Vo ₃ (=V _G ). Therefore,
Resistors 74 and 75 are connected to the base of the transistor 53.
A substantially constant voltage is generated regardless of temperature, which is determined by the ratio of the saturation currents of transistors 68 and 69.

By adjusting the values of the resistors 70 and 71 and the saturation current ratio of the transistor 53 to the transistor 52, the temperature dependence of the potential of the collectors of the transistors 51 and 52 can be arbitrarily set.

For example, by setting the collector potentials of the transistors 51 and 52 to be approximately equal to the base potential over a wide temperature range, it is possible to significantly reduce the influence of the Early effect of the transistors 51 and 52 on Vo ₁ .

Further, by setting the emitter potentials of the transistors 54 and 55 to a high potential, it is possible to prevent saturation of the transistors constituting the current source 82 at low temperatures.

When the current amplification rate of the transistors 54 and 55 is low, the collector current ratio of the transistors 51 and 52 deviates from the value determined by the ratio of the resistors 70 and 71 due to the influence of the base currents of the transistors 54 and 55.
Therefore, an error occurs in Vo ₁ . transistor 5
The saturation current ratio of 6,57 is the transistor 51,52.
This can be prevented by making the collector current ratio equal to . In general, the matching of current amplification factors between adjacent transistors in an integrated circuit is very good, so that the base current ratio of transistors 54 and 55 is equal to the collector current ratio, and in this case it is equal to the collector current ratio of transistors 51 and 52. This is because it is equal to the current ratio. At this time, by setting the saturation current ratio of the transistors 54 and 55 equal to the collector current ratio of the transistors 51 and 52, a setting error in the collector current ratio of the transistors 51 and 52 due to an error in the base potential of the transistors 54 and 55 can be avoided. can be minimized.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a reference voltage generator that can always generate a constant voltage regardless of temperature changes.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of a conventional reference voltage generator, Fig. 2 is a temperature characteristic diagram of a conventional reference voltage generator, Fig. 3 is a diagram of the principle of operation of the present invention, and Figs. 4 to 8 1A and 1B are diagrams each showing an example of the present invention. 11...Current source, 12...Transistor, 13
...Voltage adder, 14... Generator of voltage proportional to absolute temperature, 15... Output voltage, 16... Generator of voltage proportional to absolute temperature.

Claims (1)

[Claims] 1. The collector electrode of the first transistor and the collector electrode of the second transistor are
The emitter electrode of the first transistor is connected to a first reference potential via a second resistor, and the emitter electrode of the first transistor is connected to a second reference potential via third and fourth resistors connected in series. The emitter electrode of the transistor is connected to the second reference potential via the fourth resistor, and the output of an operational amplifier is connected to the collector potential of the first and second transistors as negative-phase and positive-phase inputs, respectively. In a reference voltage generator fed back to the base electrodes of the first and second transistors connected in common, a potential proportional to the magnitude of the output potential of the reference voltage generator, and an output of the reference voltage generator. A second transistor is formed by feeding back to the base electrode of the third transistor the output of an operational amplifier whose positive and negative phase inputs are the collector potential of the third transistor through which a current proportional to the magnitude of the potential flows. A voltage generator is provided, and the output potential of the reference voltage generator is corrected by a correction potential proportional to a difference potential between the output potential of the reference voltage generator and the output potential of the second voltage generator. Reference voltage generator.