JPH02227710A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To facilitate the design and the production of a reference voltage generating circuit when it is set into an integrated circuit, etc., by taking out the common base potential or the voltage proportional to this base potential as the reference voltage in a state where the emitter currents of a pair of transistors connected to a common base are kept at different levels. CONSTITUTION:The same currents I1 and I2 are supplied to the transistors TR 1 and 2 from a current source circuit 5. The common base potential Vc of both TR 1 and 2 are defined as Vc=e+kT(pRe/Ri)ln(1/m), where the coefficients (m) and (p) are decided by the structures of 1st and 2nd TRs 1 and 2 and the structure of the circuit 5 respectively. The emitter current density of the TR 2 is equal to 1/4 compared with that of the TR 1 to satisfy m=4. Based on this formula, the temperature compensation is carried out. The generated reference voltage V0 is set based on the full current value I0 supplied to both TR 1 and 2, and the individual emitter resistance value Ri is set to satisfy the temperature compensation conditions of said formula. The difference between the voltage Vc inputted to the TR 1 from the collector of the TR 2 and the reference voltage V0 inputted to the TR 2 is amplified and outputted to be amplified again by a control TR 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reference voltage generation circuit for generating a temperature-compensated reference voltage or constant voltage suitable for being incorporated into an integrated circuit or the like.

[Prior Art] Electronic circuits often require a reference voltage for their operation, and this reference voltage is required to maintain a constant value over a wide range of temperature changes.

As is well known, as a reference voltage source for semiconductor circuits, 'C is p
The nearly fixed forward voltage of the n-junction is suitable, but it is necessary to compensate for its negative temperature dependence and create a reference voltage of the desired value from it, and various measures have been taken to achieve this. . A typical conventional reference voltage generation circuit according to the fourth issue is shown.

In FIG. 4, a diode-connected transistor 11 whose collector and base are short-circuited is for a reference voltage source, and a transistor 12 whose base is commonly connected is for temperature compensation. From ■ to the common control transistor 13 and each collector resistor 1? A current is supplied through C and R2, and a reference voltage ν0 is taken out from the connection point between the control transistor 13 and both resistors 121 and R2. Therefore, if the forward voltage of the hemi-emitter junction of the transistor 11 is C, the reference voltage Vo is set higher than this by the voltage drop within the resistor R1.

On the transistor 12 side, the collector resistance R2 is set higher than the collector resistance R1 of the transistor 11, and the emitter resistance R3 is connected, so the current flowing through the base-emitter junction is lower than that on the transistor 11 side. As is well known, the base-emitter voltage is a logarithmic function of the current density in the emitter layer, and the base-emitter voltage of transistor 12 is higher than the base-emitter voltage e of transistor 11. Since it operates in a state where the voltage is low by the voltage drop across the resistor R3, the following equation approximately holds true under this condition.

Vo= e 10K T (R2/R3) Zn(R2/
R1) However, K is the Boltzmann constant and q is the electron configuration.
Then, K = a constant expressed by k/q, and T is the absolute temperature.

The base-emitter voltage e of the transistor 11 in the first term in the above equation has a negative temperature coefficient, and the second term has a positive temperature coefficient, so by appropriately selecting the values of the resistors R1 to R3, the reference Temperature compensation can be performed by setting the temperature coefficient of voltage Vo to O.

The base current of the control transistor 13 in FIG.
The auxiliary control transistor 15 whose collector is connected to the constant current source 14 also receives current from the constant current source 14, and its base receives the potential at the connection point between the transistor 12 and the resistor R2. When the reference voltage Vo is even slightly higher than the predetermined value, the base potential of the auxiliary control transistor 15 rises and its base current increases, and the constant current source 14 supplies the control transistor 13 with that amount. - Since the Sumi current decreases, the collector-base voltage of the control transistor 13 increases, and the reference voltage Vo decreases.Of course, if the reference voltage Vo becomes lower than a predetermined value, the control transistor 13 decreases its collector-base voltage and increases the reference voltage Vo.

In this way, the control transistor 13 allows the reference voltage ν to be maintained even if the load conditions of the power supply voltage ■ and the reference tjA voltage Vo vary.
0 is always controlled to a certain desired value, and the current value flowing through the transistors 11 and 12 is also kept constant, thereby stabilizing the above-mentioned temperature compensation effect.

[Problem to be solved by the invention]

As described above, in the conventional circuit described above, the reference voltage V.

can be set to a desired value by selecting the resistor R1, and kept at a constant value by the control transistor 13. However, from a design standpoint, selecting the resistance values R1-R3 is not necessarily easy, and from a manufacturing standpoint, When incorporated into an integrated circuit or the like, there is a problem in that slight manufacturing errors tend to cause large variations in the generated reference voltage value and temperature compensation performance.

The main reason for this is that the collector resistance R2 and emitter resistance R3 of the transistor 12 are involved in the two functions of reference voltage temperature compensation and planting control, and the reference voltage Vo
When determining the value of the resistor R1 to achieve the desired value, the selectable range of the resistor values u2 and R3 that satisfy both of these functions is narrow, and furthermore, their manufacturing errors tend to cause a slight difference in circuit performance. In addition, in actual production, these resistors l1
Since variations in the power generated by the constant current source 14 are likely to occur independently of the value of l-R3, variations in circuit performance are further amplified by this.

In addition to this performance, the pair of collector resistors R1 and R2 each require a fairly high resistance value, usually on the order of several ohms, so they occupy a large chip area when incorporated into an integrated circuit. Moreover, there is a problem that power consumption also increases.

It is an object of the present invention to solve such problems, to facilitate design and manufacture when incorporated into integrated circuits, etc., and to reduce variations in circuit performance.

[Means to solve the problem]

This purpose, according to the invention, consists of a pair of common base connected transistors, a common emitter resistor that receives the emitter current of both transistors, an individual emitter resistor that receives the emitter current of one of the transistors, and a A reference voltage generating circuit is configured with a current source circuit that supplies a current proportional to each other, and the emitter current densities of both transistors are made to be different from each other to generate a common base potential of both transistors or a voltage proportional to it. This is achieved by taking out the voltage as a reference voltage.

Note that it is advantageous for the current source circuit in the above configuration to utilize a current mirror circuit to supply currents proportional to each other to both transisks.

The simplest way to make the emitter current densities of both transistors different from each other is to make one of the transistors have a multichemic structure, or to make the emitter currents of both transistors different from each other. may have the same structure, but the current supplied to them from the current source circuit may be different from each other.

In addition, as described in 1jI\n above, the common base potential of both synristors is used as a reference voltage. It is desirable to extract the base W-voltage from the collector.
・Installing a transistor] For example, by dividing its collector voltage and connecting the voltage dividing point to the common base of both transistors and the same potential, a reference voltage proportional to the common -1-segment level can be applied to its L-rkk. It can be taken out from the side.

An advantageous application of the circuit of the present invention is a comparator. For example, by applying a comparison input to the common base of both transistors and taking out a comparison output from the collector side of the control transistor, a comparator can be easily constructed with a built-in reference voltage generation circuit. It is possible to construct a comparator circuit. At this time, it is preferable to take out the comparison output in the form of a current signal.

[Function] Of course, in the circuit of the present invention, it is necessary to temperature-compensate the reference voltage value, and for this purpose, as in the configuration in the previous section, a pair of transistors connected to a common base is provided to compensate for their Emink current density. and a common emitter resistor that receives emitter current from both transistors and an individual emitter resistor that receives emitter current from either of the transistors.

Hereinafter, for convenience of explanation, the one used as a reference voltage source in a pair of transistors will be referred to as the first transistor, and the one for temperature compensation will be referred to as the second transistor.
Let the values of the common and individual emitter resistances be Rc and R4, respectively.

For simplicity, it is assumed that the currents 11 and 12 of the first and second transistors are equal to each other, and that the emitter current of the latter is greater than the former, so that the emitter current density is 1/111. The current flowing through the common emitter resistor 11c is 10
．． Assuming that the base-emitter voltage of the first transistor serving as a reference voltage source is e, the common base potential Vc of both transistors is Vc=e+Rc·10. Furthermore, since the base-emitter voltage of the second transistor is lower than e in the above equation by the voltage drop across the individual emitter resistor R4 that receives the emitter current, and its value is the natural logarithm of the emitter current density, , the current of the second transistor is 12-10/2, and the following equation is obtained.

12= K T (1/RiMn(1/m)) Therefore, by inserting this into the above equation, Vc= e + K T (2Rc/Ri)in(1/
m), and as described above, the negative temperature dependence of the reference voltage source e can be compensated for by the positive temperature dependence of the second term.

The current source circuit in the above configuration supplies currents 1 and I that are proportional to each other for these first and second transistors.
2, and in the above explanation, for convenience, IL
= 12, but this is more generally 12 = (1/n
)11 and set p=n+1, the above equation further becomes Vc-e 1K T (pRc/Ri)Zn(1/+n
) (1).

Now, the coefficient Ill on the right side of the above equation depends on the structure of the first and second transistors, the coefficient p depends on the configuration of the current source circuit, and the ratio Rc/Ri depends on the relative values of the common and individual emic resistances. Since the values can be set uniquely and independently from each other, the present invention eliminates the need to set the values of the three resistors in relation to each other in order to provide the necessary functions to the circuit, as in the past, and the integrated circuit When incorporating it into a conventional J, the design and production becomes much easier,
In addition, variations in circuit performance due to manufacturing errors are also significantly reduced, thereby making it possible to solve the above-mentioned desired problem.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The figure shows a first embodiment of the reference voltage generating circuit according to the present invention.

In this embodiment, the pair of transistors consists of a first transistor l and a second transistor 2, which are connected to each other with a common base.The base-emitter voltage e of the former is used as a reference voltage source, and the latter is temperature-compensated. In this example, as shown in the figure, it is a multi-emitter transistor with four emitters and an emitter area four times that of the former, and an individual emitter resistor 4 having the aforementioned resistance value Ri is connected to it. There is. A common emitter resistor 3 having a resistance value Re is connected to both transistors 1 and 2 so as to receive their emitter currents.

It is preferable to use a current mirror circuit as shown in the figure for the current source circuit 5 (in this example, the same value is applied from the reference side transistor 5a to the first transistor 1, and from the driven side transistor 5b to the second transistor 2). current is supplied.

The control transistor 6 is of the pnp type in this example, receives the collector potential of the second transistor 2 at its base, receives the power supply voltage V at its emitter, and has its collector connected to the common base of the first and second transistors. . Therefore, in this example, the common base potential Vc is output from the collector of the control transistor 6 as the reference voltage Vo.

In the reference voltage generation circuit in this example configured as described above, the same current 11=12 is supplied from the current source circuit 5 to the transistors 1 and 2, so the above n-1, therefore, in equation (1). Since P=2 and the emitter current density of the second transistor 2 is one-fourth that of the first transistor, m=4, and temperature compensation operation based on equation (1) is performed. As is easily understood, the generated reference voltage Vo is determined by the base-emitter voltage e of the first transistor 1, the value Re of the common emitter resistor 3, and the total current supplied to the first and second transistors 1 and 2. Set by the value ■0,
Further, the value Ri of the individual emitter resistor 4 is set so as not to satisfy the temperature compensation condition of equation (1).

Next, regarding the operation of the control transistor 6, in a circuit consisting of a pair of transistors 1 and '2 and the current source circuit 5, if we consider that the connection between the bases of both transistors 1 and 2 is cut off, it can be easily understood. is equivalent to one differential amplifier circuit, and the voltage Vc is applied to the base of the first transistor l as one input, and the reference voltage Vo is applied to the base of the second transistor 2 as the other input. □ Therefore, in this example, the difference between the two power values is amplified and output from the collector end of the second transistor 2, and is further amplified by the control transistor 6 which receives the collector potential of the second transistor 2 as its base. In reality, both transistors 1 and 2 are connected to a common base, and the amplified output from the collector of the control transistor 6 is given to this, which naturally acts in the direction of negative feedback, so in reality both transistors It works to equalize the currents 11 and 12 flowing through the transistors 1 and 2, and as a control gain of this system, a high amplification factor can be obtained by combining the differential amplifier circuit and the control transistor 6.

Figure 2 shows the common base potential V of a pair of transistors 1 and 2.
, c, which generates a reference voltage VO proportional to, but different from, a second embodiment of the present invention, in which a pair of resistors 7a and 7 are connected to the collector of the control transistor 6 as shown.
A voltage dividing circuit 7 consisting of a voltage dividing circuit 7 is connected, and its voltage dividing point is connected to the same potential as the common base. As can be easily seen, in this example, the control transistor 6 always operates to make the potential of this voltage dividing point equal to the common base point potential Vc, so the resistance value of the pair of voltage dividing resistors 7a and 7b is set to Ra. and Rh, then Vo = (1+Ra/Rh)
A reference voltage controlled to be constant at Vc is generated from this embodiment circuit.

Note that the common base potential Vc and therefore this reference voltage V.

The operations of this embodiment circuit other than those described above, including temperature compensation, are exactly the same as in the case of FIG.

Also, in this case, the second transistor 2 can of course have a multi-emitter structure as shown in FIG. 1, but in this embodiment, instead, the emitter area is set to be larger than that of the first transistor 1. There is.

FIG. 3 shows an embodiment in which the present invention is applied to a comparator circuit. As shown in the diagram, the circuit configuration is almost the same as in Figure 1, but a comparative human power Vi is applied to the common base of transistors 1 and 2, and in this example, from the collector of the control I/transistor, in the form of a current signal. A comparison output to is output. As will be seen, this embodiment circuit utilizes the differential amplification function of the reference voltage generation circuit according to the present invention.
1) This is a comparator circuit with a built-in reference voltage circuit that generates Vc in the equation, and as shown in the lower right part of the figure, the value for comparison is determined according to the magnitude of the value of comparison human power Vi with respect to Vc. A comparison operation is performed in which Jlo suddenly changes.

Although it cannot be strictly said that this embodiment circuit always generates an accurate reference voltage Vc, it can at least always generate an accurate reference voltage Vc when the value of the comparison input Vi matches the original reference voltage. , perform a strict comparison operation based on it. A comparator circuit having a simple structure and incorporating such a reference voltage generating circuit has the advantage that it can be fabricated within a very small area within a chip such as an integrated circuit.

As can be seen from the embodiments described above, the present invention is not limited to the specific embodiments, but can be implemented in various modified forms, or can be applied or applied in various forms to configure electronic circuits. can do.

[Effect of the invention] As described above, in the present invention, one
A current source circuit that supplies a pair of transistors, a common emitter resistor that receives the emitter current of both transistors, an individual emitter resistor that receives the emitter current of one of the transistors, and a current that is proportional to each other to both transistors. The following effects can be achieved by configuring a reference voltage generation circuit and extracting the common base potential of both transistors or a voltage proportional to it as a reference voltage while making the emitter current densities of both transistors different from each other.

(a) As a circuit condition for temperature compensation of the reference voltage, 1
The emitter current density ratio of the paired transistors, the current ratio supplied to them from the current source circuit, and the resistance value ratio of the common and individual emitter resistors can be set uniquely and independently of each other, giving you greater freedom in setting circuit constants. The design is much simpler than before, and it is possible to generate a reference voltage of any value within a wide range.

(b) Since there is almost no interdependence between circuit constants in terms of circuit performance, and circuit operation is determined by the relative ratio of any constant such as resistance value, manufacturing errors in circuit constants are avoided when incorporating into integrated circuits, etc. Variations in circuit performance based on this method are significantly reduced compared to conventional methods, and quality control becomes easier and yields are improved.

(C) The conventionally required three resistors can be reduced to two, and all emitter resistors have low resistance values, so the chip area required to build resistors into an integrated circuit can be significantly reduced compared to conventional methods. Can be reduced.

(d) By controlling the reference voltage with high gain while utilizing the differential amplification effect of the circuit of the present invention, its temperature compensation performance can be made more complete than before, and the response to changes in the reference voltage on the load side can be improved. The reference voltage value can be controlled more precisely.

In addition, the circuit of the present invention is suitable for being incorporated into an electronic circuit such as a comparator as a built-in circuit by utilizing its differential operation. By incorporating the reference voltage generating circuit according to the present invention, including such applied circuits, into an integrated circuit device or the like, it is possible to improve the performance and economical efficiency while taking advantage of the above-mentioned advantages.

[Brief explanation of the drawing]

1 to 3 relate to the present invention; FIG. 1 is a circuit diagram of a first embodiment of the reference voltage generation circuit according to the present invention, FIG. 2 is a circuit diagram of the second embodiment, and FIG. FIG. 2 is a circuit diagram of an embodiment in which this is applied to a comparator circuit. FIG. 4 is a circuit diagram of a reference voltage generating circuit according to the prior art. In this case, a first transistor forming a 1:1 pair of transistors, a second i-transistor forming a 2:1 pair of transistors, 3: common emitter resistance, 4: individual emitter resistance, 5: current source circuit or a current mirror circuit, 5. I:
Base ¥18 side transistor, 5b: Driven side transistor,
6: Control transistor, 7: Voltage dividing circuit, 7a, 7b: Voltage dividing resistor, 11: Reference voltage source transistor, 12: Temperature compensation transistor, 13: Control transistor, 14:
Constant current source, 15: Auxiliary control transistor, e: Base-emitter voltage or reference voltage source of the first transistor, Io: Comparison output, ■0: Total current of the first and second transistors, Il: First The current of the transistor, ■2
: Current of the second transistor, Ra, Rb : Voltage division resistance value, Rc: Resistance value of common emitter resistor, Ri: Resistance value of individual emitter resistor, V: Power supply voltage, vc: Common emitter potential, vi: Comparison input , vo: reference voltage.

Claims (1)

[Claims] A pair of transistors connected with a common base, a common emitter resistor that receives the emitter current of both transistors, an individual emitter resistor that receives the emitter current of one of the transistors, and a current that is proportional to each other for both transistors. A reference voltage generator comprising a current source circuit for supplying a current, and extracting a common base potential of both transistors or a voltage proportional to the common base potential as a reference voltage with the emitter current densities of both transistors being different from each other. circuit.