JPH09331214A - Current supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current supplying circuit which can operate normally even under a low voltage and can reduce the capacitance of an oscillation preventing capacitor, chip area, and chip cost. SOLUTION: A reference voltage Vrefa is applied across the base of an npn transistor NT1 and a voltage Vrefb , a partial voltage obtained from the reference voltage Vrefa , is applied across the base of an npn transistor NT2 and a resistance element R1 is connected between the emitters of the transistors NT1 and NT2 . Then the emitter of the transistor NT2 is grounded through a resistance element R1 and the collectors of the transistors NT2 and NT1 are respectively connected to a power supply voltage VCC feed line 1 and a current mirror circuit. Therefore, the operation of a current supplying circuit is guaranteed even under a low voltage, because a current I0 which is inversely proportional to the resistance value of the resistance element R1 is outputted from the current mirror circuit and, at the same time, the oscillation preventing capacitance and chip area of the circuit can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current supply circuit that supplies a predetermined current, and more particularly to a current supply circuit that operates at a low voltage.

[0002]

2. Description of the Related Art A resistance element in an IC and an electric current flowing through the resistance element.
There is a current source that keeps the product of the flow constant regardless of temperature changes.
It is widely used. Figure 2 shows the commonly used gain system.
It is a circuit diagram showing an example of a control circuit. As shown, this example
The gain control circuit consists of a Gilbert amplifier circuit.
ing. In FIG. 2, D₀₁, D₀₂Is a diode, Q₀₁
~ Q₀₆Is an npn-type transistor, R₀₁~ R₀₄Is a resistance element
Child, I₀₁~ I₀₄Is the current source, V₀₁, V₀₂, V₀₃Is a constant voltage
Source, V _R1Is a variable voltage source, V_INIndicates the input signal source
doing. The constant voltage source V₀₂Voltage value is V, variable voltage
Source V_R1Voltage value is ΔV, input signal source V_INThe signal voltage value of
v_IN, Current source I₀₁, I₀₂Current value of I₀/ 2. Ma
Resistance element R₀₁Has a resistance of r and a resistance element R₀₃Resistance value
Is r_L, Resistance element R₀₄Has a resistance of r_INIt is.

As shown in FIG. 2, the base of a transistor Q ₀₁ is connected to a variable voltage source V _R1 and the emitter is a current source I R.
₀₁ and the collector is connected to the cathode of the diode D ₀₁ . The base of the transistor Q ₀₂ is connected to the connection point between the variable voltage source V _R1 and the constant voltage source V ₀₁ , the emitter is connected to the current source I ₀₂ , and the collector is connected to the cathode of the diode D ₀₂ . A resistance element R ₀₁ is connected between the emitters of the transistors Q ₀₁ and Q ₀₂ . Further, the anodes of the diodes D ₀₁ and D ₀₂ are connected to the constant voltage source V ₀₁ .

The base of the transistor Q ₀₃ is connected to the connection point between the collector of the transistor Q ₀₁ and the cathode of the diode D ₀₁ , the emitter is connected to the emitter of the transistor Q ₀₄ , and the collector is connected to the power supply voltage via the resistance element R _02. V
Connected to _CC supply line 1. The base of the transistor Q ₀₄ is connected to the connection point between the collector of the transistor Q ₀₂ and the cathode of the diode D ₀₂ , and the collector is the resistive element R.
It is connected to the supply line 1 of the power supply voltage V _CC via ₀₃ .

Transistor Q₀₃And transistor Q₀₄D
The connection point of the mitter is the transistor Q₀₅Connected to the collector
And the transistor Q₀₅The base is a constant voltage source V₀₃And input message
Source V_INIt is connected to the connection point with₀₃
It is connected to the. Transistor Q₀₆The base is the input signal
Source V_INConnected to the current source I ₀₄Connected to
The collector is the power supply voltage V_CCConnected to supply line 1 of
You. Also, the transistor Q₀₅Emitter and transistor
Q₀₆Resistor R between the emitter of₀₄Is connected
You.

In such a configuration, the variable voltage source V _R1
And the constant voltage source V ₀₂ , control voltage (ΔV +
V) is supplied to the base of the transistor Q ₀₁ , and the constant voltage source V ₀₁ supplies the control voltage V to the base of the transistor Q ₀₂ . Therefore, the current kI ₀ appears on the collector side of the transistor Q ₀₁ and the current (1-k) I ₀ appears on the transistor Q ₀₂ side. Here, k is (0 <k <
1) is satisfied, the variable gain of the gain control circuit is shown, and it is set by the voltage value ΔV of the variable voltage source V _R1 .

Transistor Q₀₁And transistor Q₀₂
The signal corresponding to the current difference appearing on the collector side of the
Q₀₃, Q₀₄Supplied to the base of the
If transistor Q₀₅Current I on the collector side of_CIs flowing
If so, the transistor Q ₀₃On the collector side of (1-
k) I_C/ 2, transistor Q₀₄On the collector side of_C
/ 2 currents appear respectively.

Transistor Q₀₅Appearing on the collector side of
Flow I_CIs the input signal source V_INVoltage value v _INSet by
The change is v_IN/ R_INIt is. Therefore, the output terminal T
_OUTThen, the output signal v shown in the following equation_OUTIs obtained.

[0009]

## EQU1 ## v _OUT = k (r _L / r _IN ) v _IN (1) As shown in Expression (1), the gain control circuit shown in FIG. 2 multiplies the input signal v _IN by k and outputs it. It is output as the signal v _OUT .

As described above, in the gain control circuit shown in FIG. 2, the gain k of the circuit is adjusted by controlling the control voltage ΔV, and the signal amplified by the gain k with respect to the input signal v _IN is adjusted. v _OUT is obtained.

[0011]

By the way, the above-mentioned conventional gain control circuit has a problem that the gain k of the circuit changes with temperature change.

In order to solve this, the internal resistance element R ₀₁
It is necessary to supply a current I ₀ inversely proportional to the resistance value of
As shown in FIG. 2, the gain control voltage ΔV is calculated by the following equation.

[0013]

[Number 2] ΔV = r · ΔI ... (2 ) where, r is the resistance value of the resistance element R _01, [Delta] I is the current flowing through the resistor R _01. ΔI is calculated by the following equation.

## EQU3 ## ΔI = (k-1 / 2) I ₀ (3)

Therefore, the gain control circuit has an internal resistance element.
R₀₁Current I inversely proportional to the temperature characteristics of ₀To supply
Therefore, the resistance element R₀₁The temperature characteristics of the
The gain k of the control circuit does not depend on temperature changes and is kept constant.
Be held.

FIGS. 3 to 6 show circuit diagrams of a current supply circuit which is generally used conventionally. The current supply circuit shown in FIG. 3 has a constant voltage source V _ref , diodes D _{01 to} D ₀₄ , resistance elements R ₀₁ , R ₀₂ and R ₀₃ , and npn type transistors Q _{01 to} Q.
It is composed of ₀₄ . If the resistance value of the resistance element R ₀₂ is R, the resistance value of the resistance element R ₀₁ is set to 3R. Further, the voltage of the constant voltage source V _ref is V _r, and the conduction voltages of the diodes D _{01 to} D ₀₄ are both V _B.

The base of the transistor Q ₀₁ is the resistive element R _01.
And it is connected to the connection point node ND ₀₁ with R _02, an emitter via a resistor R _03, is connected to the node ND _02, and the collector is connected to the supply line 1 of the power supply voltage V _CC. The node ND ₀₁ is connected to the constant voltage source V _ref through the resistance element R ₀₁ , and further, the diode D is connected through the resistance element R _02.
It is connected to the cathode of ₀₁ . In addition, diode D ₀₁
~ D ₀₄ are connected in series, and the anode of the diode D ₀₄ is connected to the ground line 2.

The base of the transistor Q ₀₂ is the node ND _02.
, The emitter is connected to the common connection point of the bases of the transistors Q ₀₃ and Q ₀₄ , and the collector is the power supply voltage V _CC.
Is connected to the supply line 1. Transistors Q ₀₃ , Q ₀₄
Are connected to each other, the emitters of these transistors are grounded together, the collector of the transistor Q ₀₃ is connected to the node ND _02, and the collector of the transistor Q ₀₄ is connected to the supply line 1 of the power supply voltage V _CC . .

In such a configuration, the node ND₀₁of
Constant potential source V_refVoltage value, diode D₀₁~ D₀₄
Conduction voltage and resistance element R₀₁, R₀₂Depending on the ratio of the resistance value of
Is set. For example, diode D₀₁~ D₀₄Continuity of
Both pressures are V_B, Constant voltage source V_refVoltage is V_r, Resistive element
Child R₀₁, R₀₂When the resistance values of 3R and R are
Do ND ₀₁Potential is (V_r/ 4 + 3V_B) And always one
It will be fixed.

Then, in accordance with the potential of the node ND ₀₁ , the current value I ₀ of the current flowing to the emitter side of the transistor Q _01.
Is determined. Since the current mirror circuit is composed of the transistors Q ₀₂ , Q ₀₃ and Q ₀₄ , the transistor Q
_The current I ₀ flowing on the emitter side of ₀₁ is returned to the collector side of the transistor Q ₀₄ by the current mirror circuit. That is, a predetermined current I ₀ is obtained on the collector side of the transistor Q ₀₄ .

[0020] Since the potential of the node ND ₀₁ is constant, the temperature characteristic of the resistance element R _03, if the resistance value increases, the current flowing through the resistor R _03, i.e., the transistor Q ₀₁
The current I ₀ flowing to the emitter side of is decreased, and in the opposite case, the current I ₀ is increased. Therefore, a current I ₀ inversely proportional to the temperature characteristic of the resistance element R ₀₃ can be obtained.

The current supply circuit shown in FIG. 4 comprises a constant voltage source V _ref , pnp type transistors P _{01 to} P ₀₅ , npn type transistors Q _{01 to} Q ₀₃ , resistance elements R ₀₁ and R _02, and a capacitor C _01. There is.

The base of the transistor Q ₀₁ is a constant voltage source V
_It is connected to _ref , the emitter is connected to the emitter of the transistor Q ₀₂ and the collector is connected to the common connection point of the collector and the base of the transistor P ₀₁ .
The base of the transistor Q ₀₂ is connected to a connection point between the emitter and the resistance element R ₀₂ of the transistor Q _03, the emitter is commonly connected to the emitter of the transistor Q _01, the collector is connected to the collector of the transistor P _02.

The common connection point of the emitters of the transistors Q ₀₁ and Q ₀₂ is grounded via the resistance element R ₀₁ . The bases of the transistors P ₀₁ and P ₀₂ are connected to each other, and the collector of the transistor P ₀₁ is connected to these connection points. The emitters of these transistors are connected to the supply line 1 of the power supply voltage V _CC .

The base of the transistor Q ₀₃ is connected to a common connection point between the collector of the transistor P _{02 and} the collector of the transistor Q ₀₂ , the emitter is grounded through the resistance element R ₀₂ , and the collector is connected to the node ND _03. ing.

The bases of the transistors P ₀₃ and P ₀₄ are connected to each other, their connection point is connected to the emitter of the transistor P ₀₅ , and the emitters of the transistors P ₀₃ and P ₀₄ are connected to the supply line 1 of the power supply voltage V _CC. Has been done. The base of the transistor P ₀₅ is connected to the node ND ₀₃ , and the collector is grounded. The collector of the transistor P ₀₄ is connected to the output terminal T _OUT .

A capacitor C ₀₁ is connected between the emitter and collector of the transistor P ₀₃ . In the current circuit shown in FIG. 4, the output current I ₀ is the transistor Q _03.
Since it is taken out from the collector side of the transistor, there is a problem that the loop gain is large and oscillation is likely to occur in the structure of the circuit. Therefore, in order to prevent oscillation, a capacitor C ₀₁ is connected between the emitter and collector of the transistor P _03. .

In the current supply circuit shown in FIG. 4, if the current I ₀ flows to the collector side of the transistor Q ₀₃ ,
By the current mirror circuit formed by the transistors P ₀₃ and P ₀₄ , the current I ₀ is returned to the output terminal T _OUT , that is, the predetermined current I ₀ is obtained at the output terminal T _OUT .

Resistance element R₀₂Depending on the temperature characteristics of
Resistance element R₀₂If the resistance value of the
R₀₂The voltage drop that occurs in the₀₂The
The voltage applied to the base rises. Because of this,
Star Q₀₃Base of the transistor Q₀₂Collector of
Potential drops, and the transistor Q₀₃Flow to the collector side of
Current I₀Current value becomes smaller. On the contrary, the resistance element R₀₂
When the resistance value decreases due to the temperature characteristics of
Star Q₀₃Current I flowing to the collector side of₀Has a large current value
It becomes. In this way, the output terminal T_OUTThen the resistance element R₀₂
Current I which is inversely proportional to the temperature characteristic of ₀Is obtained.

The current supply circuit shown in FIG. 5 comprises a constant voltage source V _ref , pnp type transistors P _{01 to} P ₀₄ , npn type transistors Q _{01 to} Q ₀₃ , and resistance elements R ₀₁ and R ₀₂ .

The base of the transistor Q ₀₁ is a constant voltage source V
_It is connected to _ref , the emitter is connected to the emitter of the transistor Q ₀₂ and the collector is connected to the common connection point of the collector and the base of the transistor P ₀₁ .
The base of the transistor Q ₀₂ is connected to a connection point between the emitter and the resistance element R ₀₂ of the transistor Q _03, the emitter is commonly connected to the emitter of the transistor Q _01, the collector is connected to the collector of the transistor P _02.

The common connection point of the emitters of the transistors Q ₀₁ and Q ₀₂ is grounded via the resistance element R ₀₁ . The bases of the transistors P ₀₁ and P ₀₂ are connected to each other, and the collector of the transistor P ₀₁ is connected to these connection points. The emitters of these transistors are connected to the supply line 1 of the power supply voltage V _CC .

The base of the transistor Q ₀₃ is connected to a common connection point between the collector of the transistor P _{02 and} the collector of the transistor Q ₀₂ , the emitter is grounded through the resistance element R ₀₂ , and the collector is connected to the node ND _04. ing.

The base of the transistor P _03, P ₀₄ are connected to each other, and the connection point is connected to the collector of the transistor P _03, further connected to the transistor P _03, supply line 1 of emitter supply voltage V _CC of the P ₀₄ Has been done. The collector of the transistor P ₀₄ is connected to the output terminal T _OUT .

Similar to the current supply circuit shown in FIG. 4, the current I ₀ flowing in the collector side of the transistor Q ₀₃ is returned to the output terminal T _OUT side by the current mirror circuit composed of the transistors P ₀₃ and P ₀₄ , and the current I ₀ It is output as I ₀ '.

Resistance element R₀₂Depending on the temperature characteristics of
Resistance element R₀₂If the resistance value of the
R₀₂The voltage drop that occurs in the₀₂The
The voltage applied to the base rises. Because of this,
Star Q₀₃Base of the transistor Q₀₂Collector of
Potential drops, and the transistor Q₀₃Flow to the collector side of
Current I₀Current value becomes smaller. On the contrary, the resistance element R₀₂
When the resistance value decreases due to the temperature characteristics of
Star Q₀₃Current I flowing to the collector side of₀Has a large current value
It becomes. In this way, the output terminal T_OUTThen the resistance element R₀₂
Current I which is inversely proportional to the temperature characteristic of ₀'Is obtained.

The current supply circuit shown in FIG. 6 comprises a constant voltage source V _ref , pnp type transistors P _{01 to} P ₀₄ , npn type transistors Q ₀₁ and Q ₀₂ , resistance elements R ₀₁ and R _02, and a capacitor C _01. There is.

The base of the transistor Q ₀₁ is a constant voltage source V
_It is connected to _ref , the emitter is connected to the emitter of the transistor Q ₀₂ , the collector is connected to the collector of the transistor P ₀₁ , and the connection point forms the node ND ₀₁ . The base of the transistor Q ₀₂ is connected to the connection point between the collector of the transistor P ₀₃ and the resistance element R ₀₂ , the emitter is commonly connected to the emitter of the transistor Q ₀₁ , and the collector is commonly connected to the collector and the emitter of the transistor P _02. Has been done.

The common connection point of the emitters of the transistors Q ₀₁ and Q ₀₂ is grounded via the resistance element R ₀₁ . The bases of the transistors P ₀₁ and P ₀₂ are connected to each other, and the collector of the transistor P ₀₂ is connected to these connection points. The emitters of these transistors are connected to the supply line 1 of the power supply voltage V _CC . A capacitor C is provided between the emitter and collector of the transistor P _01.
01 is connected.

Transistor P₀₃Base is node ND₀₁
And the emitter is connected to the power supply voltage V _CCConnect to supply line 1 of
And the collector is a resistive element R₀₂Is grounded through
You. Transistor P₀₄Base is node ND₀₁Connected to
And the emitter is the power supply voltage V _CCConnected to the supply line 1 of
Lector is output terminal T_OUTIt is connected to the.

In the current supply circuit shown in FIG. 6, assuming that the current I ₀ is flowing to the collector side of the transistor P ₀₃ , if the resistance value of the resistance element R ₀₂ becomes large due to the temperature characteristics, the resistance element R ₀₂ becomes large. _The voltage drop generated at ₀₂ increases, and the voltage of the node ND ₀₁ also increases accordingly. The voltage of the node ND ₀₁ is the transistor P ₀₃ ,
Since it is applied to the base of P ₀₄ , when the voltage of the node ND ₀₁ rises, the current value of the current I ₀ flowing through the collector side of the transistors P ₀₃ and P ₀₄ becomes smaller. On the contrary, when the resistance value of the resistance element R ₀₂ becomes small due to the temperature characteristic,
Current I ₀ flowing on the collector side of the transistors P ₀₃ , P ₀₄
Current value becomes large. That is, at the output terminal T _OUT , a current I ₀ inversely proportional to the temperature characteristic of the resistance element R ₀₂ is obtained.

In the current supply circuit shown in FIG. 6, current is taken out from the collectors of the transistors P ₀₁ and P ₀₃ , and there is a problem that the circuit has a high gain and is apt to oscillate. In order to prevent oscillation, it is necessary to set the capacitance value of the capacitor C ₀₁ connected between the emitter and collector of the transistor P _{01 to} a large value, for example, several tens of pF or more.
A capacitance of 100 pF is needed.

These current supply circuits generate a current I ₀ inversely proportional to the temperature characteristic of the internal resistance element, and by supplying it to the above-described gain control circuit, the temperature characteristic of the internal resistance element is canceled and the temperature It is possible to obtain a gain that is held constant regardless of changes.

However, these current supply circuits have their respective drawbacks, and in the present situation, none of them can be applied satisfactorily, especially in the case of low voltage. For example, there is a problem that the current supply circuits shown in FIGS. 3 and 4 do not operate when the power supply voltage V _CC is a low voltage of 3 V or less.

The current supply circuit shown in FIG. 5 can operate even when the power supply voltage V _CC is a low voltage of 3 V or less. But,
In this circuit, the current I ₀ flowing through the emitter of the transistor Q ₀₁ is determined by I ₀ = V _r / R. Here, R
Is the resistance value of the resistance element R ₀₂ . That is, a current I ₀ inversely proportional to the resistance value R of the internal resistance element is obtained. However, when the current I ₀ is output by the current mirror circuit composed of the pnp transistors P ₀₃ and P ₀₄ , the current I ₀ ′ obtained from the collector of the transistor P ₀₄ is usually low in h _{FE of the} pnp type transistor. , The current I ₀ '= I ₀ output from the collector of the transistor P ₀₄ does not hold, and due to variations in the pnp transistor,
The current I ₀ 'changes.

The current supply circuit shown in FIG. 6 can operate even when the power supply voltage V _CC is a low voltage of 3 V or less. But,
In this circuit, the loop gain is high because of the structure in which the current I ₀ is taken out by the collectors of the transistors P ₀₁ and P ₀₃ .
There is a problem that it easily oscillates.

As described above, in order to prevent oscillation, the capacitance of the capacitor C ₁ connected between the emitter and collector of the transistor P ₀₁ is required to be as large as several tens of pF to 100 pF, and in order to realize this, the chip area is reduced. The size of the IC chip must be increased, which causes an increase in the cost of the IC chip.

The present invention has been made in view of such circumstances, and an object thereof is to operate normally even at a low voltage, to supply a predetermined current, and to reduce the capacitance of an oscillation preventing capacitor, and An object of the present invention is to provide a current supply circuit that can reduce the area and chip cost.

[0048]

In order to achieve the above object, according to the present invention, bases are connected to a first reference power source and a second reference power source, respectively, and emitters are mutually connected via a first resistance element. First and second transistors connected to each other, a second resistance element connected between the emitter of the second transistor and a reference potential, and the first resistor
A current output circuit that is connected to the collector of the transistor and outputs a current according to the collector current to the outside.

Further, in the present invention, preferably, the second reference power supply voltage is a voltage obtained by dividing the voltage with a resistance element based on the first reference power supply, and the first reference power supply changes in temperature. It is composed of a power supply that does not depend on. further,
The resistance value of the second resistance element is set to half the resistance value of the first resistance element.

According to the present invention, a first reference voltage, for example, a constant voltage which does not depend on temperature change is applied to the base of the first transistor, and a first reference voltage, for example, is applied to the base of the second transistor. The second reference voltage obtained by voltage division by the resistance element is applied based on As a result, the first and second
If the base / emitter voltages of the transistors are equal,
The voltage difference between the emitters of these transistors becomes equal to the voltage difference between the first and second reference voltages, and a current that is inversely proportional to the resistance value of the first resistance element connected between the emitters can be obtained. It is output to the outside by the output circuit.

[0051]

1 is a circuit diagram showing an embodiment of a current supply circuit according to the present invention. As shown in the figure, the current supply circuit according to the present embodiment has resistance elements R ₁ , R ₂ , R ₃ and R.
₄ , pnp transistors PT ₁ , PT ₂ , PT ₃ , np
It is composed of n transistors NT ₁ and NT ₂ .

The emitters of the pnp transistors PT ₁ and PT ₂ are connected to the supply line 1 of the power supply voltage V _CC , the bases are connected in common, and the connection point is connected to the emitter of the pnp transistor PT ₃ . base of the pnp transistor PT ₃ is connected in common with the collector of the pnp transistor PT ₁ to node ND _3, and the collector is grounded.
The collector of the pnp transistor PT ₂ is connected to the output terminal T _O.

The collector of the npn transistor NT ₁ is connected to the node ND ₃ , and the base is connected to the input terminal T _ref of the reference voltage V _refa . Further, the resistance elements R ₃ and R ₄ are connected in series between the input terminal T _ref and the ground line 2, and the connection point of the resistance elements R ₃ and R ₄ forms a node ND ₁ .

The emitter of the npn transistor NT ₁ is connected to the node ND ₂ via the resistance element R ₁ . n
The collector of the pn transistor NT ₂ is connected to the supply line 1 of the power supply voltage V _CC , the base is connected to the node ND ₁ ,
The emitter is connected to the node ND ₂ . Further, the node ND ₂ is grounded via the resistance element R ₂ . The resistance value of the resistance element R ₁ is set to r, and the resistance value of the resistance element R ₂ is set to r / 2.

The operation of the current supply circuit will be described below with reference to FIG. During circuit operation, the reference voltage V _refa is input to the input terminal T _ref , and the npn transistor NT ₁
Applied to the base. The voltage value of the reference voltage V _refa is, for example, 1.3 to _1.5 V and is kept constant regardless of temperature change.

The reference voltage V _refa is _divided by the resistance elements R ₃ and R ₄ connected in series, and the _divided voltage V _refb is generated at the node ND ₁ . The _divided voltage V _refb is applied to the base of the npn transistor NT ₂ as the second reference voltage. The voltage value of the _divided voltage V _refb is set higher than the base / emitter voltage V _BE2 of the npn transistor NT ₂ .

Therefore, the reference voltage V _refa and the _divided voltage V
voltage difference _refb (V _refa -V _refb) has no temperature dependency,
If the currents flowing through the npn transistors NT ₁ and NT ₂ are equalized, the base / emitter voltages of these npn transistors are also equalized. That is, (V _BE1 = V _BE2 )
It is. Here, V _BE1 is the base / emitter voltage of the npn transistor NT ₁ .

Further, the npn transistors NT ₁ and NT
_Second emitter voltages, respectively V _a, when the V _b, voltage difference (V _a -V _b) also does not depend on the temperature change is held constant. The current flowing through the npn transistor NT ₁ is I
_{When the value} is ₀ , the current value i ₀ of the current I ₀ is given by the following equation.

[0059]

I ₀ = (V _a −V _b ) / r (4)

That is, the current value of the current I ₀ flowing through the npn transistor NT ₁ is inversely proportional to the internal resistance element R.
In addition, the current I ₀ is output to the output terminal T _O by the current mirror circuit configured by the pnp transistors PT ₁ , PT ₂ , and PT ₃ .

In the present circuit example, the resistance values of the resistance elements R ₁ and R ₂ are set to r and r / 2 because the current I flowing through the npn transistors NT ₁ and NT ₂ is almost the same. This is for holding at ₀ , and it is not necessary to limit to this.

In the present circuit example, the larger the value of the voltage difference (V _refa -V _refb ) between the reference voltage V _refa and the _divided voltage V _refb , the higher the accuracy, but the voltage difference is limited. Hereinafter, how to determine the voltage difference (V _refa −V _refb ) between the reference voltage V _refa and the _divided voltage V _refb and the error thereof will be described.

[0063] In order to obtain a large voltage difference (V refa -V _refb), the reference voltage V _REFA and divided voltage V _refb at normal temperature
Is set to satisfy the following equation.

[0064]

## _EQU5 ## 2 (V _refa −V _refb ) + V _BE = V _refa (5) Here, the base of the npn transistors NT ₁ and NT ₂ /
Let both emitter voltages be V _BE .

For example, the reference voltage V _refa = 1.3 at room temperature
V, V _BE = 0.7V, and the temperature characteristic of the base / emitter voltage is 2 mV / ° C. Further, the current value of the current I ₀ i ₀ =
Assuming 100 μA, the resistance value r of the resistance element R ₁ is r = 3
kΩ. Further, the _divided voltage V _refb = 1.0V, (V
_refa −V _refb ) = 0.3V.

Further, calculation results are shown for the current flowing through the npn transistor NT ₂ under two different conditions of high temperature (50 ° C.) and low temperature (-50 ° C.), ignoring the temperature characteristic of the internal resistance element. Np at normal temperature (25 ℃)
Assuming that the current value flowing through the n-transistor NT ₂ is 100 μA, the current I _2HT flowing through the npn transistor NT ₂ is about 33 μA at a high temperature of 50 ° C., and the low temperature is −50 °.
The current I _2LT flowing through the npn transistor NT ₂ is about 16
It is as large as 7 μA. In this way, the npn transistor NT
_In No. ₂ , at high temperature, about twice the current at normal temperature flows,
At low temperature, less than half the current flows at room temperature. Base / emitter voltage V _{BE of} npn transistors NT ₁ and NT ₂
Difference is about ± 18 mV.

In this circuit example, the resistance element R₁Occur in
The voltage drop is (V_a-V_b) = (V _refa-V_refb) =
Since it is 0.3V, the output current I is accurate to about ± 6%.₀
It is possible to obtain In addition, the temperature characteristics of the resistance element
Considering, the resistance element is composed of polysilicon,
Unlike ordinary resistance elements, the resistance value is small at high temperatures.
It has a so-called negative temperature characteristic. However, the resistance element
The temperature characteristics of the child are npn transistor NT₁, NT₂The
Source / emitter voltage V_BEIs smaller than the temperature characteristics of
You.

In consideration of the above, at high temperature, the voltage drop generated in the resistance element R ₁ becomes small, but the resistance value r of the resistance element R ₁ also becomes small. Therefore, the current flowing in the npn transistor NT ₁ , that is, , The current value of the current I ₀ output to the output terminal T _O does not fluctuate greatly depending on the temperature change, and the current flowing through the collector of the npn transistor NT ₂ is 33 μA to 1 of the calculation result described above.
The change amount is smaller than 67 μA.

In this example, the accuracy of the output current I ₀ is high when the power supply voltage V _CC is high, but when the voltage is low,
For example, it can operate even when the power supply voltage V _CC is 3 V or less,
Due to the above, even if the temperature changes significantly,
The accuracy of the output current I ₀ is sufficiently kept within the range of ± 6%. Further, in the circuit shown in FIG. 1, the current I ₀ is output from the collector of the pnp transistor PT ₂ forming the current mirror circuit, the loop gain of the circuit is low, and the capacitance of the oscillation preventing capacitor is small.
It may be 1 to 2 pF or less, and the area of the IC chip may be small.

As described above, according to this embodiment,
Reference voltage V_refaNpn transistor NT₁Bee
Applied to the reference voltage V_refaObtained by partial pressure by
Pressure voltage V_refbNpn transistor NT₂Mark on base
In addition, npn transistor NT ₁, NT₂Between the emitters of
Resistance element R₁To connect the npn transistor NT₂of
The emitter is a resistance element R₂Grounded through the npn tran
Vista NT₂Power supply voltage V_CCConnect to supply line 1
Continue, npn transistor NT₁Current collector
Since it is connected to the mirror circuit, the resistance element R₁Against the resistance value of
Proportional current I₀Is output by the current mirror circuit.
Operation is guaranteed even at low voltage, and a capacitor for oscillation prevention is used.
Small amount, small chip area
You.

[0071]

As described above, according to the current supply circuit of the present invention, the operation is guaranteed even in the low voltage circuit, especially when the power supply voltage V _CC is 3 V or less, and the power supply voltage V _CC used in a wide range is obtained. It can respond and generate a stable current. Further, according to the present invention, there is an advantage that the capacity for preventing oscillation is small, the pattern area can be reduced, and the cost of the IC chip can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a current supply circuit according to the present invention.

FIG. 2 is a circuit diagram of a Gilbert type gain control circuit.

FIG. 3 is a circuit diagram showing an example of a conventional current supply circuit.

FIG. 4 is a circuit diagram showing an example of a conventional current supply circuit.

FIG. 5 is a circuit diagram showing an example of a conventional current supply circuit.

FIG. 6 is a circuit diagram showing an example of a conventional current supply circuit.

[Explanation of symbols]

 R₁, R₂, R_Three, R_Four... Resistance element, PT₁, PT₂,
PT_Three... pnp transistor, NT₁, NT₂... npn
Transistor, T_ref... Reference voltage input terminal, V _CC…Power supply
Voltage, GND ... Ground potential, 1 ... Power supply voltage V_CCSupply line,
2 ... Ground wire.

Claims (6)

[Claims] 1. A first transistor and a second transistor whose bases are connected to a first reference power source and a second reference power source, respectively, and whose emitters are connected to each other via a first resistance element, and the above-mentioned first and second transistors. A second resistance element connected between the emitter of the second transistor and the reference potential; and a current output circuit connected to the collector of the first transistor and outputting a current according to the collector current to the outside. Current supply circuit having a. 2. The current supply circuit according to claim 1, wherein the second reference power supply voltage is a voltage obtained by dividing the voltage with a resistance element based on the first reference power supply. 3. The current supply circuit according to claim 1, wherein the first reference power supply is composed of a power supply independent of temperature change. 4. The resistance value of the second resistance element is the first resistance value.
The current supply circuit according to claim 1, wherein the resistance value is set to half of the resistance value of the resistance element. 5. The current supply circuit according to claim 1, wherein the current output circuit comprises a current mirror circuit. 6. The current supply circuit according to claim 5, wherein the current mirror circuit is a Wilson current mirror circuit.