JPH06138968A - Reference voltage generation circuit - Google Patents

Abstract

PURPOSE:To keep a power supply voltage low by eliminating an active load as the load of a current mirror circuit. CONSTITUTION:A resistance R1 which generates DELTAVBE being the VBE difference between transistors Q1 and Q2 is connected to the emitter of an n-side transistor Q2 making a current mirror of 1:n with the transistor Q1. A reference voltage Vo is taken out of an output transistor Q7 which accepts a base bias from a load resistance. As the load of the transistors Q1 and Q2, no active load is provided but the only resistance load is provided. The two collector potential of the transistors Q1 and Q2 is differentialy amplified by a differential amplifier and the output is negatively fed back to the base of the transistors Q1 and Q2 so that the collector potentials are made equal. As no active load is provided as the load of the current mirror circuit, the power supply voltage can be kept low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a built-in reference voltage generation circuit, and in particular, a circuit for correcting variations in base-emitter voltage V _BE due to variations in transistor saturation current Is, which is constant regardless of fluctuations in power supply voltage. And a reference voltage generation circuit that outputs a stable voltage.

[0002]

2. Description of the Related Art The right half of FIG. 3 shows a conventional example of a reference voltage generating circuit. Q1 is the first transistor, Q2
Is a second transistor having an emitter area that is n (n> 1) times the emitter area of the first transistor, and the bases of both transistors are connected to each other.
The emitter of the first transistor Q1 is directly grounded, while the emitter of the second transistor Q2 is the first.
Is grounded through the resistor R1. R6 is first at one end
Is connected to the collector of the transistor Q1 and the other end is connected to the bases of the first transistor Q1 and the second transistor Q2.

Q3, Q4, and Q5 are pnn transistors forming a Wilson type current mirror circuit. Q3 and Q5 are in a current mirror relationship, and the collector of the transistor Q5 is connected to the collector of the second transistor Q2. The collector of the transistor Q4 connected in series with the transistor Q3 is connected to the resistor R6 and the bases of the first and second transistors Q1 and Q2. R2
Is a resistor connected between the emitter of the transistor Q2 and the power supply V _CC terminal, and R3 is a resistor connected between the emitter of the transistor Q5 and the power supply V _CC terminal. Resistance R2
R and R3 have the same resistance R between the terminals on the side opposite the power supply terminal
4 and R5 are connected in series, and the connection point between the resistors R4 and R5 is the reference voltage output transistor Q.
7 is connected to the base.

The output transistor Q7 has a collector connected to the power supply terminal and an emitter connected to the grounded-emitter transistor Q7.
This transistor Q6 is connected to the collector of 6
A current equal to the collector current of the transistor Q8 flows through the current mirror circuit composed of the transistors Q9 to Q11, and the base of the transistor Q8 has a resistor R6 and a first transistor Q1. It is connected to the connection point.

The principle of this conventional reference voltage generating circuit will be described. The current flowing through the first transistor Q1 is I
If the current flowing through the first and second transistors Q2 is I2, their load resistors R2 and R3 are equal to each other, and the Q transistors Q3 and Q4, which are active loads, are also 1: 1 current mirrors. R1 has a difference ΔV _BE (= V _BE 1-V) between V _BE of the transistors Q1 and Q2.
_BE 2. Incidentally, V _BE, V _BE 2 is Q2 of V _BE of V _BE 1 is Q1)
Is generated as a terminal voltage. By the way, V _BE 1 = V _BE 2
+ I2 · R1 and therefore V _BE 1−V _BE 2 = I2 ·
Is _{R1, V BE = (k ·} T / q) · l n (I / Is)
And k · T / q = V _T , the following equation holds. _{ΔV BE = V BE 1-V} BE 2 = V T · [l n (I / Is1) -l n (I / Is2)] = V T · l n (Is2 / Is1) = V T · l n n Hisashi , Q: electron charge, k: Boltzmann constant, T: absolute temperature

[0006] Then, I1 = I2 becomes the current mirror circuit Q3 to Q5, therefore, ΔV _BE · R3 / R1 is generated as each terminal voltage to the resistor R2 and the resistor and the value of R3 is equal to the resistance R2 R3. On the other hand, the base of transistor Q8 voltage V _BE 1-I values obtained by subtracting the V _BE 1 from I2 · R6 is V _BE of the first transistor Q1
2 · R6, the current flowing through the transistor Q8 is changed to I
4, I4 = I1 / exp (R6 · I1 / V _T ).
Becomes Then, the same current as the current I4 flows to the base of the transistor Q6 by the current mirror circuit composed of the transistors Q9 to Q11.
6 collector current, ie, reference voltage output transistor Q7
The emitter current I3 of the above becomes I4 · h _FE (Q6). That is, this emitter current I3 becomes a parameter that depends on h _FE .

The collector-emitter voltage Vo of the output transistor Q7 is (ΔV _BE / R3 / R1) + V _BE
(Q7), and therefore has a positive temperature characteristic ΔV _BE
And V _BE (Q7) having a negative temperature characteristic, the temperature characteristic can be canceled to obtain a voltage Vo having no temperature dependence, which is output as a reference voltage. Incidentally, V _BE in the equation for Vo is V _T · l _n (Ic
/ Is), and if Is (saturation current) varies, V _BE also varies accordingly. Therefore, the fact that Is has a correlation with h _FE is used to generate a current in which Ic depends on h _FE , thereby suppressing variations in the output reference voltage Vo due to variations in V _BE .

The right half of FIG. 3 is a temperature proportional current generating circuit. Q32 and Q36 form a current mirror circuit with each other and have an emitter area ratio of 1: n. The emitter of the transistor Q32 is grounded via the resistor R27, and the emitter of the transistor Q36 is connected via the resistor R28. It is connected to the connection point between the transistor Q32 and the resistor R27. Q33, Q35, and Q37 form a current mirror circuit, and form an active load on the transistors Q32 and Q36 that form the current mirror circuit.
Q34 is a transistor that applies a base potential to the transistors Q32 and Q36. Q38 is transistor Q3
2, Q36 is a temperature proportional current output transistor having a current mirror relationship, the emitter is grounded through a resistor R29, and the collector current is the output temperature proportional current Io.

Next, the principle of the temperature proportional current generating circuit will be described. Transistor Q32 and transistor Q36
Since the load of the transistor Q33 and Q37 has a 1: 1 current mirror configuration,
The currents I5 and I6 flowing through the transistor 32 and the transistor Q36 are equal to each other, but since the emitter areas are different, the V
_BE difference, i.e. _{ΔV BE (= V T · l} n n. Here, the ratio of the emitter area of Q36 relative emitter area of Q32 and n in) is generated as the terminal voltage of the resistor R28. This is the same principle as in the case of the reference voltage generating circuit.

[0010] Then, the resistor R27 flowed to the resistor R28 the current (i.e., [Delta] V _BE / R28) since twice the current flows, the terminal voltage is a voltage of 2 · V _BE · R27 / R28 is generated. Then, the transistor Q38 and the transistor Q
The emitter areas of 32 are made equal, and the terminal voltage of the resistor R27 is made equal to the terminal voltage of the resistor R28.
If the value of 29 is set, Io becomes equal to the current I5 flowing through the transistor Q32. And I5
= Because it is _{ΔV BE / R28 = V T ·} l n n / R28 = Io, after all, the output current Io of the temperature-proportional current generating circuit is a current proportional to temperature. This is used for temperature compensation.

[0011]

By the way, in the conventional reference voltage generating circuit, as a load of the first transistor Q1 and the second transistor Q2, in addition to the resistors R2 and R3, a pnp is provided.
Since the active load including the current mirror formed of the transistors Q23 to Q5 is included, there is a problem that the minimum required voltage as the power supply voltage is high. The minimum required power supply voltage for the reference voltage generation circuit shown in Fig. 1 is V _BE (Q1)
+ V _CE (Q4) + V _BE (Q3) + VR2 (terminal voltage of the resistor R2), 0.75 + 0.3 + 0.75 + 0.5
= 2.3V. By the way, it seems that it can be driven by a power supply of 3V because it is about 2.3V, but considering the fluctuation of the power supply voltage due to noise or the like, a margin of about 1V is required.

Therefore, it cannot be used with a 3V power supply. However, there is a strong demand for lowering the power supply voltage of an electronic device using an IC from a 5V power supply to a 3V power supply, and it is necessary to make efforts to meet the demand. However, the conventional reference voltage generating circuit shown in FIG. It is virtually impossible to meet that demand. Further, in the past, the temperature proportional current generating circuit had to be constructed completely independently of the reference voltage generating circuit as shown in FIG. Therefore, it has been restricted to simplify the circuit configuration of the IC and reduce the size of the IC.

The present invention has been made to solve such a problem, and one object thereof is to construct a current mirror with the first transistor and the transistor, and to make the emitter area n (n> n). 1) A second transistor having a double emitter area, a first resistor connected to the emitter side of one of the two transistors, and a load connected to the collectors of the first and second transistors. A reference voltage generating circuit comprising at least a second and a third resistor and a reference voltage output transistor for receiving a base current supplied via the second and the third resistor to generate a reference voltage from between the collector and the base. Another purpose is to reduce the power supply voltage of the voltage generation circuit.The other purpose is to provide the reference voltage generation circuit with the function of generating temperature proportional current, In eliminating the voltage generating circuit and the need to separately and independently provided by.

[0014]

According to a first aspect of the present invention, there is provided a reference voltage generating circuit having a current ratio of 1: n and a first resistor having a current ratio of 1: n and a resistor generating a V _BE difference ΔV _BE. Only a resistive load is provided as the load of the current mirror circuit composed of the second transistor, and the potential between the connection point between the first transistor and the load and the connection point between the second transistor and the load is set by the differential amplifier. Differentially amplified to the first and second
It is characterized in that negative feedback is provided to the base of the transistor. A reference voltage generating circuit according to a second aspect of the present invention is the reference voltage generating circuit according to the first aspect, which comprises a current mirror with the first and second transistors and has a temperature proportional current output transistor whose collector current is a temperature proportional current. Is characterized by.

[0015]

According to the reference voltage generating circuit of claim 1, the first,
Only the second and third resistors are present as the load of the current mirror circuit including the second transistor and the first resistor,
Since there is no active load, the power supply voltage is low, and theoretically, the power supply voltage can be about 1.5V. The differential amplifier is configured such that the potential difference between the connection point between the first transistor and the load resistance and the connection point between the second transistor and the load resistance becomes zero.
Drive the second transistor,
The state where ΔV _BE is generated in the first resistor connected to the emitter of the second transistor can be maintained. Therefore, first,
It is possible to maintain the normal operation of the reference voltage generating circuit whose main part is the current mirror circuit including the second transistor and the first resistor.

According to the reference voltage generating circuit of the second aspect, the first and second transistors and the first resistor of the reference voltage generating circuit are defined as the V _BE difference ΔV _BE of the two transistors necessary for generating the temperature proportional current. Since the ΔV _BE generated by the current mirror circuit is composed of the temperature proportional current output transistor, the temperature proportional current output transistor is added to the reference voltage generation circuit. It can also play a role.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reference voltage generating circuit of the present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a circuit diagram showing one embodiment of the reference voltage generating circuit of the present invention. This embodiment is shown in FIG.
Although it is largely different from the reference voltage generation circuit shown in the left half of the figure in that a differential amplifier is used, there are some common points, and the common points have already been described, and the description thereof is omitted. Only explained. The same reference numerals are used for common parts throughout the drawings.

In this reference voltage generating circuit, there is no Wilson type current mirror active load composed of pnp transistors Q3 to Q5, and the collector of the first transistor Q1 is a terminal on the side opposite to the power source terminal of the second resistor R2. In addition, the collector of the second transistor Q2 is directly connected to the terminal on the side opposite to the power supply terminal of the resistor R3. a is a connection point between the first transistor Q1 and the second resistor R2, and b is a connection point between the second transistor Q2 and the third resistor R3.

Q16 to Q20 and R9 and R10 apply the two potentials at the connection points a and b to the transistor Q14 and the resistor R.
7 and a transistor Q15 and a resistor R8 to form a differential amplifier that receives and differentially amplifies via a level shift circuit. The input terminal of the differential amplifier for receiving the inverting input receives the input of the collector b of the second transistor Q2, the input terminal for receiving the non-inverting input thereof receives the input of the collector a of the first transistor Q1, and the inverting output thereof is the transistor Input from Q20 to the bases of the first and second transistors Q1 and Q2. Therefore, the first and second transistors Q1 and Q2 are controlled by this differential amplifier so that the potential difference between the connection points a and b becomes zero. To be done.

R6 has a first and second transistor Q at one end.
1, a resistor connected to the base of Q2, the other end of which is connected to the collector of the common-emitter transistor Q13 and the base of the common-emitter transistor Q12, and
The base of the transistor Q13 is connected to the bases of the first and second transistors Q1 and Q2, and the same current as the collector current of the transistor Q12 is applied to the transistors Q9 to Q9.
A current mirror circuit composed of Q11 allows a current to flow through the transistor Q6 as a base current.

Next, the operation of the reference voltage generating circuit shown in FIG. 1 will be described. As described in the description of the operation of the reference voltage generating circuit shown in FIG. 3, the second and third resistors R2 and R3 are provided.
The terminal voltages of are equal to each other. And the connection points a and b
The potential of is negatively fed back to the bases of the first and first transistors Q1 and Q2 through the differential amplifier so that the potential difference becomes 0, so ΔV _BE is sufficiently generated in the first resistor R1. If not, the following operation will be performed.

That is, the base voltages of the transistors Q1 and Q2 are the same, and the emitter area is larger than that of the transistor Q1.
2 is larger (n times larger), the collector current of the second transistor Q2 is larger than that of the first transistor Q1. Therefore, the potential of the connection point b is lower than the potential of the connection point a. Become. When the potential of the connection point b is low, the differential amplifier works to raise the potential of the base c. Then,
Finally, ΔV _BE is generated in the first resistor R1.

When ΔV _BE occurs in the first resistor R1, the collector current Ic of the first transistor Q1 becomes I
c = Is · exp (V _BE / V _T ), the collector current of the second transistor Q2 increases exponentially as the potential of the base c increases, while the collector current of the second transistor Q2 increases. Since the resistor R1 is connected to the emitter of, the resistance of the base c increases only linearly with the increase of the potential of the base c. Therefore, the potential at the connection point a becomes lower than the potential at the connection point b, and the differential amplifier acts to lower the level of the base c of the first and second transistors Q1 and Q2. Therefore, in the reference voltage generation circuit, the potentials at the connection points a and b become equal, and the state where ΔV _BE is generated in the first resistor R1 is maintained.

On the other hand, the emitter current of the output transistor Q7 must be a current dependent on h _FE .
The following is a description of this point. Since the first transistor Q1 and the transistor Q13 form a current mirror, when the emitter area of the transistor Q13 is set to be the same as that of the first transistor Q1, the transistor Q13 has a collector of the first transistor Q1. The same current as the current I1 flows as a collector current. Therefore, the base-emitter voltage of the transistor Q12 becomes a value obtained by subtracting R6 · I1 from V _BE of the transistor Q13, and therefore the transistor Q12 has a current equal to the collector current of the transistor Q8 of the reference voltage generating circuit shown in FIG. It flows as a collector current I4.

Therefore, the current I flowing through the transistor Q6
3 becomes h _FE times the collector current I3 of the transistor Q12 and becomes a current dependent on h _FE . Therefore, it is possible to output the reference voltage Vo in which the variation of V _BE of the power supply voltage output transistor Q7 due to Is is corrected.

The loads on the first and second transistors Q1 and Q2 for generating ΔV _BE are the second and third resistors R2 and R2.
Since there is no active load consisting of the current mirror circuit composed of the transistors Q3 to Q5, which is composed of only R3 and existed in the conventional reference voltage generating circuit, the minimum required value for the power supply voltage is the transistor. Q1
A current I4 equal to the collector current of 2 is applied to the transistor Q6.
Is defined by the voltage required for the operation of the current mirror circuit (comprising transistors Q9 to Q11) for flowing to the base. Specifically, V _BE (Q11) + V _BE (Q1
0) + V _CE (Q12) = 0.75 + 0.75 + 0.3V
It is possible to operate with a power supply voltage of = 1.8V.

Therefore, according to this reference voltage generating circuit, 3
Even if the power supply voltage of V is accommodated, there is a margin of 1.2 V, and it is possible to sufficiently cope with the reduction of the power supply voltage. And p
If np type transistors Q11 and Q9 having a high h _FE are used, the need for the current mirror circuit to be a Wilson type becomes sparse, and the collector-base short type can be used. Then, the transistor Q10 is not necessary, and further reduction of the power supply voltage is allowed, and if the margin is not taken into consideration, the reference voltage generation circuit can operate even if the power supply voltage is 1.5V.

FIG. 2 is a circuit diagram showing another embodiment of the reference voltage generating circuit of the present invention. The present embodiment is largely different from the embodiment shown in FIG. 1 in that it also has a function of outputting a temperature proportional current, but in terms of circuit configuration, the resistor 3 is added to the embodiment shown in FIG.
This is the one with one transistor and one transistor added, and most of them are common. Since the common part has already been described, detailed description will be omitted and only different points will be described.

Q21 is a temperature proportional current output transistor which outputs a temperature proportional current Io, and the emitter area is made equal to the emitter area of the first transistor Q1 in this example,
The base is the first and second transistors Q1,
It is connected to the base of Q2 and the emitter is resistor R13.
Grounded through.

R11 is the first and second resistors including the first resistor R1.
Is connected between the current mirror circuit composed of the transistors Q1 and Q2 and the ground and the resistor R1 is connected to the emitter.
3 is connected for level adjustment between the output transistor Q21 and the transistors Q1 and Q2, and a current twice as large as the current of the resistor R13 flows.
It has a double resistance value. Therefore, the terminal voltage of the resistor R11 becomes equal to the terminal voltage of the resistor R13, and there is no level imbalance between the transistors Q1 and Q21 forming the current mirror. R12 is also a resistor connected between the emitters of the transistors Q12 and Q13 and the ground for level adjustment, and has a resistance value twice that of the resistor R11.

The reference voltage generating circuit shown in FIG. 2 generates a temperature proportional current ΔV _BE formed by a current mirror circuit which is composed of first and second transistors Q1 and Q2 and a first resistor R1 which are essential parts. The output transistor Q21 is realized by making the output transistor Q21 and the first transistor Q1 a current mirror.

That is, the conventional temperature proportional current generating circuit (see FIG.
(See the right half of FIG. 2), the role of the transistor Q32 in the first transistor Q1, the role of the transistor Q28 in the second transistor Q2, the role of the resistor R28 in the first resistor R1, and the role of the transistor Q38. By using the reference voltage generating circuit of FIG. 1 as it is, by simply adding one transistor Q21 and three resistors R11 to R13, not only the reference voltage generating circuit but also the temperature proportional It can also be used as a current generation circuit. Therefore, there is no need to provide the temperature proportional current generating circuit separately from the reference voltage generating circuit.

Needless to say, in the reference voltage generating circuit shown in FIG. 2 as well, the Wilson type current mirror circuit composed of Q9 to Q11 may be of the base-collector short type because of the low power supply voltage. In addition, FIG.
The present invention can be implemented in a mode in which each transistor in each of the embodiments is replaced with a transistor having an opposite conductivity type, and the differential amplifier is not limited to the illustrated one.

[0034]

The reference voltage generating circuit according to the first aspect of the present invention is 1: n.
The current mirror circuit has a current ratio of 1 and one of which is connected to a resistor generating a V _BE difference ΔV _BE, and only a resistive load is provided as a load of the current mirror circuit including the first and second transistors. And a connection point between the load and a load thereof and a connection point between the second transistor and a load thereof are negatively fed back to the bases of the first and second transistors by the differential amplifier. It is a thing.
Therefore, according to the reference voltage generating circuit of claim 1,
Only the second and third resistors are present as the load of the current mirror circuit including the second transistor and the first resistor,
Since there is no active load, the power supply voltage can be low, and theoretically, the power supply voltage of about 1.5 V can be used for operation.

According to another aspect of the present invention, there is provided a reference voltage generating circuit.
In the reference voltage generating circuit, the first and second transistors form a current mirror, the emitter is grounded through a resistor, and the temperature proportional current output transistor has a collector current that is a temperature proportional current. It is a thing. Therefore, according to the reference voltage generating circuit of claim 2, the V _BE difference ΔV _BE of the two transistors required to generate the temperature proportional current is calculated from the first and second transistors and the first resistor of the reference voltage generating circuit. Since it uses ΔV _BE generated in the current mirror circuit and draws it out through the temperature proportional current output transistor, the role as the temperature proportional current generation circuit can be obtained only by adding the temperature proportional current output transistor as a transistor to the reference voltage generation circuit. You can also take it.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing one embodiment of a reference voltage generating circuit of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the reference voltage generating circuit of the present invention.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

Q1 first transistor Q2 second transistor R1 first resistor R2 second resistor R3 third resistor Q7 reference voltage output transistor Q21 temperature proportional current output transistor [Delta] V _BE first and V _BE difference Vo of the second transistor Output reference voltage Io Output temperature proportional current

Claims (2)

[Claims] 1. A first transistor and a current mirror formed with the transistor and having an emitter area of n.
A second transistor having (n> 1) times the emitter area, a first resistor connected to the emitter side of one of the two transistors, and a load connected to the collectors of the first and second transistors. Voltage generating circuit including at least a second and a third resistor, and a reference voltage output transistor that receives a base current via the second and the third resistor and generates a reference voltage between the collector and the emitter. In the above, the collector of the first transistor and the second resistor forming the load are directly connected to the collector of the second transistor and the third resistor forming the load, respectively, and the first transistor and the second resistor are connected. The potential at the connection point with
A reference voltage generating circuit provided with a differential amplifier which receives a potential between a connection point of the second transistor and the third resistor and negatively feeds back an output to the bases of the first and second transistors. 2. The reference voltage generating circuit according to claim 1, further comprising a temperature-proportional current output transistor which forms a current mirror with the first and second transistors and has a collector current that is a temperature-proportional current.