JP2001117654A - Reference voltage generating circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable reference voltage with respect to the fluctuation of operating temperature and circuit power supply voltage. SOLUTION: A leakage current removing circuit 21 is arranged, so that the leakage currents of a transistor Q3 and a transistor Q5 can be prevented from being included in currents so as to be supplied to the serially connected circuit of a resistance R2 and a diode Q6 in a band gap circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference voltage generation circuit used for a semiconductor integrated circuit (hereinafter, referred to as an IC), and more particularly to a reference voltage generation circuit in which a fluctuation in an output voltage caused by a leakage current is reduced.

[0002]

2. Description of the Related Art In recent years, low power consumption has been demanded for ICs, and a reference voltage generating circuit used for the IC has also been required to operate with a small current. Such a conventional example will be described with reference to the drawings. FIG. 3 is a circuit diagram thereof. This reference voltage generation circuit receives a bandgap circuit 1 that outputs a voltage Vb stabilized with respect to a voltage fluctuation of a circuit power supply Vcc and a fluctuation in an operating temperature, and the voltage is input to the bandgap circuit 1 between an output terminal Out and a ground line. Negative feedback is performed at a feedback ratio determined by the provided dividing resistors R3 and R4, and the amplifier 2 obtains an output voltage amplified at a predetermined amplification factor.

[0003] Reference numeral 3 denotes a start-up circuit for making the operation of the bandgap circuit 1 start up smoothly when the circuit power supply Vcc is turned on. The starting circuit 3 has a circuit power source V
cc, a drain is connected to a predetermined point (described later) of the bandgap circuit 1, and a gate is connected to a ground line via a parallel connection circuit of a resistor R10 and a capacitor C. When,
The constant current source 4 supplies a predetermined current from the circuit power supply Vcc to the capacitor C. Immediately after the circuit power supply Vcc is turned on, the starter circuit 3 activates the transistor Q10
Since the gate voltage is the voltage of the ground line, it is sufficiently lower than the source voltage (voltage of the circuit power supply Vcc). Therefore, the transistor Q10 is ON and connects the circuit power supply Vcc to a predetermined point of the bandgap circuit 1. Thereafter, when the charging of the capacitor C by the constant current source 4 progresses, the voltage gradually increases, and when approaching the voltage of the circuit power supply Vcc, the transistor Q10 is turned off, and becomes irrelevant to the operation of the bandgap circuit 1 thereafter.

Next, the band gap circuit 1 will be described. The band gap circuit 1 includes P-channel MOS type transistors Q1, Q2, Q5 and an N-channel M
A constant current circuit portion composed of each of the OS type transistors Q3 and Q4 and the resistor R1, and a load portion formed by a series connection circuit of a resistor R2 and a diode Q6 formed of a PN junction to which the output current is given. . The gates of the transistors Q1 and Q2 are connected to each other, and the respective sources are connected to the circuit power supply Vcc. The drain of the transistor Q1 is connected to its gate. That is, the transistors Q1 and Q2 constitute a first mirror circuit with the transistor Q1 as an input side. The drain of the transistor Q3 is connected to the drain of the transistor Q1, and the source is connected to the ground line via the resistor R1. The transistor Q4 has a drain connected to the drain of the transistor Q2, a source connected to the ground line, a gate connected to the drain, and a gate connected to the transistor Q3. Then, the drain of the transistor Q10 of the starting circuit 3 is connected to the drain of the transistor Q4.

In the part described above, the circuit power supply Vc
When c is turned on, since the transistor Q10 is in the ON state, the gate voltages of the transistors Q3 and Q4 are high, and they are in a state where current can flow. Then, a current flows from the transistor Q1 to the transistor Q3 to the resistor R1. Then, although the same gate voltage is applied to the transistor Q2 mirror-connected to the transistor Q1, almost no current flows because the voltage of the drain is still high, and almost all the current flowing to the transistor Q4 is initially supplied from the transistor Q10. . When the capacitor C is charged and the gate voltage of the transistor Q10 rises and the supplied current decreases, the transistor Q10
The current flowing through 2 increases, and transistor Q10 is turned off
In this state, all the current flowing through the transistor Q4 becomes the current flowing through the transistor Q2, and the current flowing through each current path is balanced at a predetermined current value, and becomes a stable state. Here, the current I flowing through the transistor Q1 (current flowing through the transistor Q3) in the stable period is the resistance R
1, but is set to a small current value such that the transistor Q3 performs an unsaturated operation.

The circuit described above is a constant current circuit in which the current I hardly changes even if the voltage of the circuit power supply Vcc is changed, although detailed description is omitted. The current I has a positive temperature coefficient with respect to a change in the operating temperature.

Therefore, as shown in FIG. 3, if a load composed of a series connection of a resistor R2 and a diode Q6 is connected between the transistor Q1 and the drain of the transistor Q5 constituting the second mirror circuit and the ground line, the mirror ratio (this 1 /
The current according to 1) flows, and the voltage Vb is output using the drain of the transistor Q5 as the output terminal of the bandgap circuit 1. That is, Vb = IR2 + Vf (1). (However, Vf is the voltage drop of the diode.) Therefore, Δ (Vb) / ΔT = R2 · ΔI / ΔT +
I · Δ (R2) / ΔT + Δ (Vf) / ΔT (2) where T is the operating temperature. By the way, Δ (Vf) / ΔT
Is a negative value, as is well known, and a rather wide T
Can be treated as a constant value in the range. Assuming that R2.ΔI / ΔT is positive as described above, and I.Δ (R2) / ΔT is negligible compared to both, by selecting R2, Δ2
(Vb) / ΔT = R2 · ΔI / ΔT + Δ (Vf) / ΔT
= 0. Since we choose R2 like this,
As a result, the output voltage Vb of the band gap circuit 1 is determined. In order to obtain a desired voltage, the amplifier 2 is required. The output terminal of the amplifier 2 is used as the output terminal Out of the reference voltage generation circuit, and the circuit power supply Vc
This is to generate a stable voltage with respect to the fluctuation of the voltage c and the operating temperature.

[0008]

However, in the above-mentioned circuit actually configured as an IC, the transistor Q3 is controlled by the voltage of its gate, and in addition to the original current flowing from the drain to the source, and from the drain to the ground. There is a leak current I1 flowing through the line. That is, the current I of the transistor Q1 is larger than the current that should flow by I1. Further, in the transistor Q5, there is a leak current I2 flowing from the source to the drain in addition to the current I controlled by the gate voltage.
Since the leak current I2 also flows through the resistor R2 and the diode Q6, the current flowing through the resistor R2 and the diode Q6 is obtained by adding I1 + I2 to the original current. It is good if the leakage currents I1 and I2 are small and can be ignored with respect to the original current. However, if the original current is set small, it cannot be ignored. These leak currents depend on the operating temperature in a positive relationship, and increase as the voltage applied to that portion increases. Therefore, the output of the reference voltage generation circuit includes an error that fluctuates due to a change in the operating temperature or the circuit power supply voltage. Therefore, the present invention provides a stabilized reference voltage generating circuit which eliminates the influence of such a leakage current.

[0009]

In order to solve the above-mentioned problems, the present invention is of one conductivity type, in which a source (emitter) is connected to one end of a circuit power supply and a gate (base) is connected to a drain (collector). The connected input side transistor common to the first and second mirror circuits, the output side transistor of the first mirror circuit, and the drain (collector) of the input side transistor common to the first and second mirror circuits. )
A drain (collector) is connected to the other end of the circuit power supply via a first resistor, and a transistor of another conductivity type; and an output transistor of the first mirror circuit. The drain (collector) is connected to the drain (collector), the source (emitter) is connected to the other end of the circuit power supply, the gate (base) is connected to the drain (collector), and the gate (base) of the constant current transistor is connected. ), A load transistor of another conductivity type, an output transistor of the second mirror circuit, a drain (collector) of the output transistor of the second mirror circuit, and the other end of the circuit power supply. In a reference voltage generating circuit comprising a series connection circuit of a diode and a second resistor connected therebetween, an output side transformer of the second mirror circuit is provided. The leakage current monitoring transistor, in which the source (emitter) is connected to one end of the circuit power supply and the gate (base) is connected to the source (emitter), and the constant current transistor, are designed in the same manner as the transistor. Similarly, the source (emitter) is connected to the other end of the circuit power supply, the drain (collector) is connected to the drain (collector) of the leak current monitoring transistor, and the gate (base) is connected to the drain (collector). A position where the drain is shunted to remove the current injected into the series connection circuit of the diode and the second resistor, having the same design as the input-side transistor of the third mirror circuit and the constant current transistor, which are connected. And an output transistor of a third mirror circuit connected to the reference voltage generating circuit. According to the above circuit configuration, the leakage current monitoring transistor in the OFF state in which the gate (base) is connected to the source (emitter) has a leakage current close to the leakage current generated in the output side transistor of the second mirror circuit. Occurs, and the current is transferred to the output transistor of the third mirror circuit. Furthermore, a leak current close to the leak current flowing from the drain (collector) of the constant current transistor to the other end of the circuit power supply is generated in the output side transistor of the third mirror circuit, and eventually the output of the third mirror circuit is output. The side transistor subtracts the current obtained by adding both the leak currents from the current to be supplied by the output side transistor of the second mirror circuit and injects the current into the series connection circuit of the diode and the second resistor.

[0010]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram thereof. This reference voltage generating circuit configured as an IC differs from the conventional circuit shown in FIG. 3 in the bandgap circuit 20. More specifically, a leakage current removing circuit 21 is added to the bandgap circuit 1 in FIG.

The parts of the amplifier 2 and the starting circuit 3 are the same as those shown in FIG.

Next, with respect to the bandgap circuit 20, the same parts as in FIG. 3 will be described again. In this band gap circuit 20, a P-channel MOS transistor Q1,
The gates of Q2 are connected to each other, and their sources are connected to a circuit power supply Vcc (one end of the circuit power supply) to which a positive voltage is applied. And the transistor Q1
Is connected to its gate. That is, the transistors Q1 and Q2 configure the first mirror circuit 11 with the transistor Q1 as an input side.

N-channel MOS transistor Q3
Is a constant current transistor whose drain is connected to the drain of the transistor Q1 and whose source is connected to the ground line (the other end of the circuit power supply) via the resistor R1.
The drain of the N-channel MOS transistor Q4 is connected to the drain of the transistor Q2,
The source is connected to the ground line, the gate is connected to the drain, and the transistor Q3 is connected to the gate to serve as a load transistor for the transistor Q2. Then, the drain of the transistor Q10 of the starting circuit 3 is connected to the drain of the transistor Q4.

A transistor Q1 and a P-channel MOS transistor Q5 forming the second mirror circuit 12 are provided as output transistors in the same design as the transistor Q1, and a resistor R2 is provided between the drain and the ground line. A load connected in series with the diode Q6 is connected.

The parts described above are the same as those of the conventional circuit shown in FIG. 3, and the operation is substantially the same. That is, the resistor R that determines the current I flowing through the transistor Q1
1 is that the transistor Q3 is set so as to have a small current value such that the transistor Q3 becomes non-saturated. The transistor Q3 flows from the drain to the source under the control of the gate voltage, and passes through the resistor R1. In the transistor Q5, there is a leak current I2 flowing from the source to the drain in addition to the current I controlled by the gate voltage, in addition to the fact that there is a leak current I1 flowing from the drain to the ground line in addition to the current. R1 and resistance R
2 is similar to the conventional circuit shown in FIG. 3 in that the relationship with 2 is selected so as to eliminate the temperature coefficient of the output voltage Vb of the bandgap circuit 20. However, the bandgap circuit 20 is provided with a leak current removing circuit 21 that extracts the leak currents I1 and I2 from the current supplied by the transistor Q5 so as not to flow to the series connection circuit of the resistor R2 and the diode Q6. different.

The leakage current elimination circuit 21 is composed of a leakage current monitoring transistor Q21, an input transistor Q22 and an output transistor Q23 constituting a third mirror circuit 23. The transistor Q21 has the same design as the transistor Q5, and the source is the circuit power supply Vc.
connected to the gate, the gate is connected to the source and always off
It is in a state. Transistor Q22 has the same design as transistor Q3, with the source connected to the ground line, the gate connected to the drain, and the drain connected to the drain of transistor Q21. Transistor Q23 has the same design as transistor Q3, with the source connected to the ground line, the gate connected to the gate of Q22, and the drain connected to the drain of transistor Q5.

Since the leak current monitoring transistor Q21 is OFF, only the leak current flows. The magnitude of the current is close to the leak current I2 flowing from the source to the drain of the transistor Q5. The current is mirrored on the transistor Q23 as the current controlled by the gate. In the transistor Q23, a leak current similar to the leak current I1 flowing from the drain of the transistor Q3 to the ground line is generated from the drain to the ground line. Therefore, the leak current removing circuit 21 extracts a current approximating the combined current of the leak current I1 and the leak current I2 from the drain of the transistor Q5.

According to the reference voltage generating circuit of this embodiment configured as described above, the current supplied to the series connection circuit of the resistor R2 and the diode Q6 is obtained by removing the leak current generated in the transistors Q3 and Q5. Therefore, the output voltage Vb of the bandgap circuit 20 becomes more stable with respect to the voltage fluctuation of the circuit power supply Vcc and the fluctuation of the operating temperature. Is also stable.

FIG. 2 is a circuit diagram showing another embodiment of the present invention. In this figure, the starting circuit and the amplifier are not shown, and only the bandgap circuit 30 is shown. In this circuit, each of the transistors Q1, Q2, Q3, Q4, Q5, Q21, Q in the first embodiment shown in FIG.
22 and Q23 are each configured by connecting two transistors in series. By doing this,
Variations in the output voltage Vb of the bandgap circuit with respect to variations in the circuit power supply Vcc can be further reduced. still,
In this circuit, the point at which the current corresponding to the leak current is extracted is not from the drain of the transistor Q5b but from the drain of the transistor Q5a, but the effect is not so different from either.

In the first and second embodiments, the circuit power supply is set to a positive voltage and a positive reference voltage is obtained. Each transistor uses a MOS type.
P-channel MOS type to PNP type, N-channel MOS type to NP with drain as collector and gate as base
If it is read as an N-type, the same can be applied to a device using a bipolar transistor.

Furthermore, if a negative voltage is applied to the circuit power supply Vcc and the conductivity type of each transistor is reversed (in this case, the direction of the diode Q6 is also reversed), the bandgap circuit outputs a negatively stabilized output. By outputting the voltage Vb, a stable reference voltage can be obtained. Further, the present invention can be similarly carried out whether the transistor used is a MOS type or a bipolar type.

[0022]

As described above, according to the reference voltage generating circuit of the present invention, it is possible to reduce the uncontrolled leakage current from being mixed with the current for generating the output voltage of the bandgap circuit included therein. Therefore, a more stable reference voltage can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a band gap circuit according to another embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional reference voltage generation circuit.

[Explanation of symbols]

11 First mirror circuit 12 Second mirror circuit 23 Third mirror circuit Q1, Q1a, Q1b P-channel MOS transistor (input side transistor common to first and second mirror circuits) Q2, Q2a, Q2b P Channel MOS transistor (output side transistor of first mirror circuit) Q3, Q3a, Q3b N-channel MOS transistor (constant current transistor) Q4, Q4a, Q4b N-channel MOS transistor (load transistor) Q5, Q5a, Q5b P-channel MOS transistor (output side transistor of second mirror circuit) Q6 Diode Q21, Q21a, Q21b P-channel MOS transistor (leakage current monitoring transistor) Q22, Q22a, Q22b N-channel MOS type Transistors (input transistors of the third mirror circuit) Q23, Q23a, Q23b N-channel MOS transistor (output-side transistor of the third mirror circuit) R1 first resistor R2 second resistor Vcc circuit power supply

Claims (9)

[Claims] An input transistor of one conductivity type, having a source connected to one end of a circuit power supply and a gate connected to a drain, common to the first and second mirror circuits, and the first mirror. An output transistor of the circuit, a drain connected to a drain of an input transistor common to the first and second mirror circuits, and a source connected to the other end of the circuit power supply via a first resistor. A constant-current transistor having a conductivity type; a drain connected to the drain of the output-side transistor of the first mirror circuit; a source connected to the other end of the circuit power supply; a gate connected to the drain; A load transistor of another conductivity type, connected to the gate of the current transistor, an output transistor of the second mirror circuit, and an output of the second mirror circuit. It is connected between the other end of the drain side transistor and a circuit power diode and a second
A reference voltage generating circuit having a series connection circuit with a resistor, wherein the source is connected to one end of the circuit power supply and the gate is connected to the source, similarly to the design of the output transistor of the second mirror circuit. Connected, the leak current monitoring transistor, the same design as the constant current transistor, the source is connected to the other end of the circuit power supply, the drain is connected to the drain of the leak current monitoring transistor, the gate Is connected to the drain, and has the same design as the input side transistor of the third mirror circuit and the constant current transistor, and shunts the current that the drain injects into the series connection circuit of the diode and the second resistor. A reference voltage generation circuit, comprising: a third mirror circuit output-side transistor connected to a position to be removed. 2. A P-channel type having a source connected to a positive voltage circuit power supply and a gate connected to a drain,
A drain connected to an input-side transistor common to the first and second mirror circuits, an output-side transistor of the first mirror circuit, and a drain of an input-side transistor common to the first and second mirror circuits; A source is connected to a ground line via a first resistor, and an N-channel type constant current transistor; a drain is connected to a drain of an output transistor of the first mirror circuit; and a source is a ground line. An N-channel load transistor, having a gate connected to the drain and a gate connected to the constant current transistor; an output transistor of the second mirror circuit; A series connection circuit of a diode and a second resistor connected between the drain of the output transistor of the mirror circuit and the ground line A reference voltage generation circuit comprising: a leakage current monitoring transistor having a source connected to the circuit power supply and a gate connected to the source, having the same design as the output-side transistor of the second mirror circuit; An input side of a third mirror circuit, having a source connected to a ground line, a drain connected to the drain of the leak current monitoring transistor, and a gate connected to the drain, having the same design as the constant current transistor. A third mirror circuit having the same design as the transistor and the constant current transistor, having a drain connected to a position for shunting and removing a current injected into the series connection circuit of the diode and the second resistor; A reference voltage generation circuit comprising: a side transistor. 3. An N-channel type having a source connected to a negative voltage circuit power supply and a gate connected to a drain,
A drain connected to an input-side transistor common to the first and second mirror circuits, an output-side transistor of the first mirror circuit, and a drain of an input-side transistor common to the first and second mirror circuits; A source connected to the ground line via the first resistor, a P-channel type constant current transistor; a drain connected to the drain of the output transistor of the first mirror circuit; and a source connected to the ground line. Connected, a gate connected to the drain, and connected to the gate of the constant current transistor, a P-channel type load transistor; an output transistor of a second mirror circuit; A series connection circuit of a diode and a second resistor connected between the drain of the output transistor and the ground line; In the negative reference voltage generating circuit, a leakage current monitoring transistor having a source connected to the circuit power supply and a gate connected to the source, having the same design as the output-side transistor of the second mirror circuit, An input side of a third mirror circuit, having a source connected to a ground line, a drain connected to the drain of the leak current monitoring transistor, and a gate connected to the drain, having the same design as the constant current transistor. In the same design as the transistor and the constant current transistor, the drain was connected to a position for shunting and removing the current injected into the series connection circuit of the diode and the second resistor.
A reference voltage generating circuit, comprising: a third mirror circuit output transistor. 4. The relationship between the first and second resistors is selected such that a drain of an output transistor of the second mirror circuit outputs a voltage stabilized with respect to an operating temperature. 4. The reference voltage generating circuit according to 2 or 3. 5. An input transistor common to the first and second mirror circuits, which is of one conductivity type, has an emitter connected to one end of the circuit power supply, and has a base connected to the collector, and a first mirror circuit. And a collector connected to a collector of an input transistor common to the first and second mirror circuits, and an emitter connected to the first transistor.
A constant current transistor of the other conductivity type, connected to the other end of the circuit power supply through the resistor of the first mirror circuit, a collector connected to the collector of the output side transistor of the first mirror circuit, and an emitter connected to the circuit power supply A load transistor connected to the other end, having a base connected to the collector and connected to the base of the transistor for constant current, of another conductivity type; an output transistor of the second mirror circuit; And a second diode connected between the collector of the output transistor of the second mirror circuit and the other end of the circuit power supply.
A reference voltage generating circuit having a series connection circuit with a resistor of the second type, wherein the emitter is connected to one end of the circuit power supply and the base is connected to the emitter in the same design as the output transistor of the second mirror circuit. Connected, the leak current monitoring transistor, the same design as the constant current transistor, the emitter is connected to the other end of the circuit power supply, the collector is connected to the collector of the leak current monitoring transistor, the base Is connected to the collector, and has the same design as the input-side transistor of the third mirror circuit and the transistor for constant current, and shunts the current that the collector injects into the series connection circuit of the diode and the second resistor. An output transistor of a third mirror circuit connected to a position to be removed. . 6. A first PNP-type power supply, wherein an emitter is connected to a positive voltage circuit power supply, and a base is connected to a collector.
An input-side transistor common to the second mirror circuit; an output-side transistor of the first mirror circuit; a collector connected to a collector of the input-side transistor common to the first and second mirror circuits; Is the first
An NPN-type constant current transistor connected to the ground line through the resistor of the first mirror circuit, a collector connected to the collector of the output side transistor of the first mirror circuit, an emitter connected to the ground line, and a base Is connected to the collector and is connected to the base of the constant current transistor, the load transistor being of NPN type, the output transistor of the second mirror circuit, and the output transistor of the second mirror circuit. A reference voltage generating circuit comprising a series connection circuit of a diode and a second resistor connected between a collector and a ground line, the output voltage of the second mirror circuit being the same as that of the output transistor, A transistor connected to a circuit power supply and a base connected to the emitter, a leakage current monitoring transistor; An input-side transistor of a third mirror circuit, the emitter being connected to the ground line, the collector being connected to the collector of the transistor for monitoring leakage current, and the base being connected to the collector, in the same design as the In the same manner as the constant current transistor, the output side transistor of the third mirror circuit connected at a position where the collector shunts and removes the current injected into the series connection circuit of the diode and the second resistor. A reference voltage generation circuit, comprising: 7. A first NPN-type power supply, wherein an emitter is connected to a negative voltage circuit power supply, and a base is connected to a collector.
And an input transistor common to the second mirror circuit; an output transistor of the first mirror circuit; a collector connected to a collector of the input transistor common to the first and second mirror circuits; First
A constant current transistor of a PNP type connected to a ground line via a resistor of the first type, a collector connected to a collector of an output side transistor of the first mirror circuit, an emitter connected to the ground line, and a base Is connected to the collector and is connected to the base of the constant current transistor, and is a PNP-type load transistor; an output transistor of the second mirror circuit; and a collector of the output transistor of the second mirror circuit. A negative reference voltage generation circuit comprising a series connection circuit of a diode and a second resistor connected between the diode and a ground line, the same design as the output side transistor of the second mirror circuit, A leakage current monitoring transistor having an emitter connected to a circuit power supply and a base connected to the emitter; In the same manner as the first transistor, the emitter is connected to the ground line, the collector is connected to the collector of the leak current monitoring transistor, and the base is connected to the collector. The output transistor of the third mirror circuit is connected to a position where the collector is shunted to the current injected into the series connection circuit of the diode and the second resistor, and has the same design as the current transistor. A reference voltage generation circuit, characterized in that: 8. The relationship between the first and second resistors so that the drain of the output transistor of the second mirror circuit outputs a voltage stabilized with respect to the operating temperature and the voltage of the circuit power supply. 8. The reference voltage generating circuit according to claim 5, 6 or 7, which is selected. 9. A method according to claim 1, wherein a plurality of transistors are connected in series for a part or all of said transistors.
9. The reference voltage generation circuit according to 6, 7, or 8.