JP2749159B2 - Constant voltage circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a constant voltage circuit, and more particularly to a constant voltage circuit formed in a semiconductor integrated circuit. Temperature dependence of an output voltage of the constant voltage circuit itself without increasing power consumption. And a pair of first and second transistors having different emitter sizes, and a first resistor connected to the collector side of one of the second transistors having a smaller emitter size. And the second and third resistors respectively connected to the collector and the emitter of the other first transistor having a large emitter size, and the first transistor having a large emitter size relative to the voltage fluctuation of the constant voltage source. And a fourth resistor connected between the base and emitter of the third transistor and the third transistor and the base of the third transistor. The third transistor based on a change in potential on the collector side of the first transistor having a large emitter size.
And a feedback unit that controls the current of the constant voltage source to compensate for the voltage fluctuation of the constant voltage source.The emitter size is set such that the temperature dependency of the output voltage of the constant voltage circuit tends to be negative. An element having a forward diode characteristic is connected to the collector terminal side of the large first transistor.

The present invention relates to a constant voltage circuit, and more particularly, to a constant voltage circuit formed in a semiconductor integrated circuit.

In an integrated circuit, there are provided many constant voltage circuits for supplying a constant voltage to various circuits such as a logic circuit. In recent years, as resistance elements formed in various circuits and the like, polysilicon resistors have been employed in place of diffusion resistors in which junction capacitances serve as parasitic capacitances in order to increase the speed of integrated circuits. However, since the polysilicon resistor has a negative temperature coefficient, it is necessary to form a constant current source having a small dependence on temperature. As a result, in order to form a constant current source having small temperature dependence, it is required that the constant voltage circuit has an output voltage that tends to be negative with respect to temperature.

[Prior Art] Conventionally, various constant voltage circuits have been formed in a semiconductor integrated circuit to supply a constant voltage to a logic circuit or the like.
One of them is a constant voltage circuit shown in FIG. This circuit includes a current mirror unit including resistors R3, R4, R6 and transistors Q2, Q3, and a feedback unit including a transistor Q1 and a resistor R2.

The current mirror unit makes the emitter size of the transistor Q2 several times larger than the emitter size of the transistor Q3, and changes the current flowing through the transistor Q3 due to the fluctuation of the constant voltage Vout to the transistor Q2 having a large emitter size.
The current flowing through the resistor R3 is always constant,
That is, the voltage drop of the resistor R3 is kept constant. Therefore, when the voltage Vout of the constant voltage source fluctuates, for example, rises, the voltage drop of the resistor R3 is constant regardless of the rise, so that the potential at the collector terminal of the transistor Q2 is raised.

The potential of the base terminal of the transistor Q1 in the feedback section rises by an amount corresponding to the rise of the potential. Lower by minutes. Therefore, a constant voltage Vout is always supplied to the transistor Q4. As a result, a constant current Iout is always supplied to the resistor R7.

Note that the voltage drop of the resistor R1 is small and the transistor Q4
If the voltage Vout applied to the base of the
As shown in the figure, between the resistors R1 and R3 and between the resistor R1 and the base terminal of the transistor Q4, an equal number (in this case, one each) of the voltage drop and the diode
D2 and D3 are connected respectively.

In recent years, in a semiconductor integrated circuit, a polysilicon element has been used instead of a diffusion resistance in which a junction capacitance acts as a parasitic capacitance in order to increase the speed of the integrated circuit. However, while the diffusion resistance has a positive temperature coefficient, the polysilicon resistance has a negative temperature coefficient.
The current Iout rises and does not become constant, causing a problem. Therefore, in the feedback section, a resistor R2 is connected between the base and the emitter of the transistor Q2, and the current Io flows to make the temperature dependency of the output voltage Vout of the constant voltage circuit negative.

Then, as a result of conducting a test on the temperature dependency of the constant voltage circuit, as shown in FIG. 24, the current (current source output) Iout flowing through the resistor R7 with respect to the temperature has a smaller variation as the current Io flowing through the resistor R2 increases. I understood. Therefore, the current Io
It can be seen that it is sufficient to increase.

[Problems to be Solved by the Invention] However, the current Io may be increased, but the current flowing through the constant voltage circuit itself increases and the power consumption increases. Was an obstacle.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has as its object to reduce the temperature dependency of the output voltage of the constant voltage circuit without increasing the power consumption of the constant voltage circuit itself. It is to provide a voltage circuit.

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of a constant voltage circuit according to the present invention.

The constant voltage circuit includes a current mirror section and a feedback section, and is connected to a pair of first and second transistors Q2 and Q3 having different emitter sizes and to a collector side of a second transistor Q3 having a small emitter size. A current mirror section is constituted by the first resistor R6 and the second and third resistors R3 and R4 connected to the collector and the emitter of the first transistor Q2 having the other large emitter size, respectively. A constant voltage Vout applied via a resistor R1 to a base terminal of a transistor Q4 for supplying a constant current Iout to a resistor R7 made of, for example, polysilicon having a negative temperature coefficient via a first resistor R6. The voltage is applied to the second transistor Q3.

An element D1 having a forward diode characteristic is connected to the second resistor R3 so that the temperature dependency of the constant voltage Vout tends to be negative.

On the other hand, a third transistor Q1 having a base terminal connected to the collector terminal of the first transistor Q2, a collector terminal connected to the resistor R1, and a fourth transistor Q1 connected between the base and the emitter of the third transistor Q1. The feedback unit is constituted by the resistor R2.

[Operation] When the temperature rises, the voltage drop in the element D1 having the forward diode characteristic becomes smaller, and the potential on the collector terminal side of the first transistor Q2 is raised accordingly, and Third based on the rise of
It is estimated that the current is controlled by the transistor Q1 and the constant voltage Vout is small, that is, the temperature dependency shows a negative tendency.

Accordingly, as a result, the current Iout fluctuates and tends to increase as the temperature rises and the resistance value of the resistor R7 decreases, but the constant voltage Vout supplied to the transistor Q4 decreases. The rise of the current Iout is suppressed, and the current Io is always kept at a constant value.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. For convenience of explanation, the same components as those in FIGS. 22 and 23 will be described with the same reference numerals.

FIG. 2 shows an embodiment, in which a resistor is provided on the collector side of the transistor Q3 having a small emitter size in the current mirror section.
R5, R6 and a voltage drop transistor Q7 (corresponding to the diode D3 in FIG. 23) are connected. The collector of the other transistor Q2 having a large emitter size is connected via a resistor R3 to a transistor Q5 as an element having a forward diode characteristic, and the transistor Q5 is connected to a voltage dropping transistor Q6 (see FIG. 23). (Corresponding to the diode D2).

Then, the constant voltage Vout applied to the base terminal of the transistor Q4 for supplying the constant current Iout to the resistor R7 made of, for example, polysilicon having a negative temperature coefficient is applied to the transistor Q3 via the resistor R5. ing.

As a result of conducting a test on the temperature dependency in the constant voltage circuit configured as described above, as shown in FIG. 3, the current (current source output) Iout flowing through the resistor R7 with respect to the temperature is equal to the
Compared to the temperature dependence of the conventional constant voltage circuit shown in FIG. 24, the negative tendency was larger. That is, for example, a resistor
When the current Io flowing through R2 is set to 0.2 mA, the temperature dependency shows a slightly positive tendency in FIG. 24, but in FIG.
It is 1 mA, which indicates that the constant voltage circuit in the present embodiment could have a negative tendency of temperature dependency.

This means that, when the temperature rises, the voltage drop in the transistor Q5, which has a forward diode characteristic, becomes smaller, and the potential on the collector terminal side of the transistor Q2 is raised by that much, and the potential rises. The current is controlled by the transistor Q1 based on the constant voltage Vo
It is estimated that ut is small, that is, the temperature dependency shows a negative tendency.

Therefore, according to the present embodiment, the current source output can be made constant without increasing the current Io flowing through the resistor R2.

4 to 21 show another embodiment of the present invention.
Each embodiment is configured by partially changing the example in FIG.

FIG. 4 omits transistors Q6 and Q7,
In FIG. 5, a resistor R8 for preventing noise is provided between the collector of the transistor Q1 in the feedback section and the resistor R1. FIG. 6 shows a resistor R9 for noise prevention provided on the collector side of the transistor Q6 for voltage drop, and FIG. 7 shows a resistor R10 provided for noise prevention on the collector side of the transistor Q7 for voltage drop.

FIG. 8 shows that a resistor R11 for preventing oscillation is provided between the base terminals of the transistors Q2 and Q3, and FIG. 9 shows that a resistor R14 for preventing noise is provided between the base terminal of the transistor Q6 and the resistor R1. FIG. 10 shows a configuration in which a resistor R15 for preventing noise is provided between the base terminals of the transistors Q6 and Q7.

11 to 14 show a case where a capacitor for preventing oscillation is provided.In FIG. 11, a capacitor C1 is provided between the base and collector terminals of the transistor Q1, and in FIG. 12, transistors Q2 and Q3 are provided.
13, a capacitor C3 between the resistor R1 and the ground in FIG. 13, and a capacitor C4 between the base terminal of the transistor Q4 and the ground in FIG.
Is provided.

In FIG. 15, a constant current source I1 is provided in place of the resistor R1, so that the current flowing through the transistor Q1 is reduced. FIG. 16 is provided with a diode D2 in place of the transistor Q6, and FIG. 17 is provided with a diode D3 in place of the transistor Q7 so as to achieve higher integration.
FIG. 18 shows a configuration in which a diode D1 is provided in place of the transistor Q5 so as to achieve higher integration.

In FIG. 19, a diode D4 is provided instead of the transistor Q3 to achieve integration. FIG. 20 aims at integration by omitting the resistor R6, and FIG. 21 uses a transistor Q8 in parallel with the transistor Q7 to change the outlet of the output voltage Vout and use the transistor Q4 as a diode. It is like that.

[Effects of the Invention] As described above in detail, according to the present invention, the temperature dependency of the output voltage tends to be negative and the current source output is made constant without increasing the power consumption of the constant voltage circuit itself. There is an excellent effect that can be.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is an electric circuit diagram showing one embodiment of the present invention, FIG. 3 is a graph showing the relationship between temperature and current source output in one embodiment. 4 to 21 are electric circuit diagrams showing different embodiments, FIGS. 22 and 23 are electric circuit diagrams showing a conventional constant voltage circuit, and FIG. 24 is a temperature and current source output in the conventional constant voltage circuit. 6 is a graph showing a relationship with the graph. In the figure, D1 is an element having forward diode characteristics, Q1, Q2, and Q3 are transistors, and R2, R3, R4, and R6 are resistors.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-116114 (JP, A) JP-B-3-14231 (JP, B2)

Claims (1)

(57) [Claims] 1. A pair of first and second transistors (Q2, Q3) having different emitter sizes and a first transistor connected to the collector of a second transistor (Q3) having a smaller emitter size. A resistor (R6) and second and third resistors (R3, R3) connected to the collector and emitter sides of the other first transistor (Q2) having a large emitter size, respectively.
4) a current mirror section in which the potential on the collector side of the first transistor (Q2) having a large emitter size relative to the voltage fluctuation of the constant voltage source fluctuates; and a third transistor (Q1) and the current mirror section. A fourth resistor (R2) connected between the base and the emitter, the third transistor (Q2) being based on a change in potential on the collector side of the first transistor (Q2) having a large emitter size;
And 1) a current feedback control section for controlling the voltage fluctuation of the constant voltage source. The emitter size is set so that the temperature dependency of the output voltage of the constant voltage circuit tends to be negative. A constant voltage circuit, wherein an element (D1) having a forward diode characteristic is connected to the collector terminal side of the large first transistor (Q2).