JPH05251954A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To generate a reference voltage whose voltage is less than 1.2V independently of a temperature change through the use of a power supply voltage of 1.2V or below by using an output voltage with the sum of a specific voltage and another specific voltage. CONSTITUTION:Bipolar transistors(TRs) TR11, TR12 are operated at a different current density. An operational amplifier A11 controls a current of MOS TRs M11, M12 so that a potential of a node N11 is equal to that of a node N12. A current flowing to a TR M12 is expressed as betaVBE/R11, where betaVBE is a difference between base-emitter voltages of the TRs TR11, TR12. An operational amplifier A12, a resistor R12 and a MOS TR M13 control that a base-emitter voltage VBE1 of the TR11 is fed across the resistor R12. A current flowing to a resistor R13 is expressed as alphaVBE, betaVBE1. A reference voltage Vref generated across the resistor R13 is a reference voltage of 1.2V or below independently of temperature by selecting properly constants alpha, beta.

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, and more particularly to a reference voltage generation circuit for generating a low voltage of 1.2 V or less with a power supply voltage of 1.2 V or less.

[0002]

2. Description of the Related Art Conventionally, a reference voltage generating circuit used in an LSI uses, for example, a bipolar transistor manufactured of silicon, and has a band gap voltage of about 1.
The reference voltage of 2V was generated. FIG. 4 shows such a reference voltage generating circuit. The voltage V _G is applied to the bases of the bipolar transistors Tr ₁ and Tr _{2 having} different current densities, and the resistors R ₁ and R ₂ are connected in series to the emitter of the bipolar transistor Tr ₁ . A resistor R ₂ 'is connected to the emitter of the bipolar transistor Tr ₂ . Further, at the other end of the resistors R ₂ and R ₂ ', a MOS transistor M _{1 that} operates as a current source
Are connected.

Operational amplifier A₁Inverting input and non-inverting input
Since the potentials at the ends are equal, the bipolar transistor T
r₁, Tr₂Base-emitter voltage V_BE1, V_BE2
Difference voltage ΔV_BEIs resistance R₁Have joined. Therefore,
Anti-R₁Current flowing through is ΔV_BE/ R ₁And this current becomes
Resistance R₂Resistance R₂The voltage across both ends is ΔV_BE
× R₂/ R₁Becomes Where node N₁And voltage V_GAmong
If the voltage is the reference voltage Vref,

[0004]

[Equation 1] Becomes That is, the reference voltage Vref is equal to the voltage V _BE1 and ΔV.
_The voltage is the sum of the _BE amplified voltage.

The base-emitter voltage V _BE of a bipolar transistor decreases as the temperature rises, but the difference voltage ΔV _BE rises because the rate of decrease of bipolar transistors having different current densities is different. Become. Therefore, by appropriately selecting (R ₁ + R ₂ ) / R ₁ , it is possible to cancel each other by the amount of decrease in the voltage V _{BE and} the amount of increase in the voltage ΔV _BE , and obtain a reference voltage that is invariant to temperature changes. ..

FIG. 3 is a diagram showing another reference voltage generating circuit using the above principle. When the voltage applied to the resistor R ₃ is ΔV _BE , which is the difference voltage between the base-emitter voltages V _BE3 and V _BE4 of the bipolar transistors Tr ₃ and Tr ₄ , the current flowing through the resistor R ₃ is ΔV _BE / R ₃ , and MO
Assuming that the W / L ratio of the S transistors M ₃ and M ₄ is N: 1, the current flowing through the resistor R ₄ is (N + 1) times the current flowing through the resistor R ₃ , so the voltage applied to the resistor R ₄ is Δ
V _BE × (N + 1) R ₄ / R ₃ . Therefore, the reference voltage Vref is

[0007]

[Equation 2] And

[0008]

[Equation 3] By properly selecting, it is possible to obtain a reference voltage that is invariant to temperature changes.

[0009]

The circuits shown in FIGS. 4 and 5 can generate a silicon bandgap voltage of about 1.2 V, but cannot be used at a power supply voltage lower than that. .. Therefore, it is an object of the present invention to provide a reference voltage generation circuit that generates a reference voltage of 1.2 V or less using a power supply voltage of 1.2 V or less without depending on a temperature change.

[0010]

According to the present invention, there is provided a voltage ΔV _{BE which} is a difference between base-emitter voltages of first and second bipolar transistors which operate at different current densities, and
Base-emitter voltage V of the bipolar transistor of
_In a reference voltage generating circuit that obtains a reference voltage by using _BE , the output voltage is the sum of a voltage that is α times the voltage ΔV _BE and a voltage that is 1 / β of the voltage V _BE (where β> 1). Is a reference voltage generating circuit.

In order to generate a voltage which is the sum of the voltage α times the voltage ΔV _BE and the voltage β 1 of the voltage V _BE ,
A voltage that is α times the voltage ΔV _BE and a voltage that is 1 / β of the voltage V _BE are added, and this added voltage can be used as the reference voltage. Alternatively, the voltage ΔV _BE and the voltage V _BE may be converted into currents, currents that are α times and β times smaller are generated, and these currents may be added to perform current-voltage conversion. The multiplication / division of current is achieved by using a current mirror circuit. Further, a charge amount corresponding to a voltage that is α times the voltage ΔV _BE and a charge amount corresponding to a voltage that is 1 / β of the voltage V _BE are added to generate a reference voltage that corresponds to the added charge amount. May be. Multiplication and addition of charges is achieved by a switched capacitor circuit.

[0012]

According to the present invention, the amplification factor of voltage ΔV _BE and voltage V _BE
By selecting the division ratio of _BE , it is possible to generate a reference voltage of 1.2 V or less, which hardly changes with a temperature change, at a power supply voltage of 1.2 V or less.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. 1, 2 and 3 show a reference voltage generating circuit according to the present invention. FIG. 1 shows an example of current multiplication, FIG. 2 voltage, and FIG. In addition, the same reference numerals are given to the same elements, and repeated description is omitted.

[0014] In FIG. 1, Tr ₁₁ and Tr ₁₂ are bipolar transistors, R _11, resistor R ₁₂ and R ₁₃ each resistance value R _{11 is, R 12, R 13, M} 11 ~M 15 are MOS transistors, A ₁₁ And A ₁₂ are operational amplifiers. The bipolar transistors Tr ₁₁ and Tr ₁₂ operate at different current densities. To do this, for example, the size of the emitters should be different, or the MOS
This is achieved by making the W / L ratios of the transistors M ₁₁ and M ₁₂ different.

Further, the operational amplifier A ₁₁ has MOS transistors M ₁₁ and M ₁₂ so that the potentials of the nodes N ₁₁ and N ₁₂ become equal.
Control the current of. Therefore, the difference voltage ΔV _BE between the base-emitter voltages V _BE1 and V _BE2 of the bipolar transistors Tr ₁ and Tr ₂ is applied to both ends of the resistor R ₁₁ . Therefore, the current flowing through the resistor R ₁₁ becomes ΔV _BE / R ₁₁ , and this current also flows through the MOS transistor M ₁₂ . The output of the operational amplifier A ₁₁ is also applied to the MOS transistor M ₁₅ to form a current mirror circuit. Therefore,
W of MOS transistor M ₁₂ and MOS transistor M ₁₅
If the ratio of / L is 1: M, the current flowing through the MOS transistor M ₁₅ is ΔV _BE × M / R ₁₁ .

Further, the operational amplifier A ₁₂ , the resistor R _12, and the MO
The S transistor M ₁₃ constitutes a voltage-current conversion circuit, and the base-emitter voltage V of the bipolar transistor Tr ₁₁ is
The _BE1 and converts it into a current of V _BE1 / R _12. That is, the emitter of the bipolar transistor Tr ₁₁ is connected to the inverting input terminal of the operational amplifier A ₁₂ , and therefore V _DD -V
_BE1 voltage is input, and MOS transistor M ₁₃
In order to make the drain of the same have the same potential, the voltage V _BE1 is controlled to be applied across the resistor R ₁₂ . Therefore, M
A current of V _BE1 / R ₁₂ flows through the OS transistor M ₁₃ .

The output of the operational amplifier A ₁₂ is also applied to the gate of the MOS transistor M ₁₄ to form a current mirror circuit. When the ratio of W / L of the MOS transistor M ₁₃ and the MOS transistor M ₁₄ is N: 1, a current of V _BE1 / (R ₁₂ × N) flows through the MOS transistor M ₁₄ . Since the current flowing through the resistor R ₁₃ is the sum of the current flowing through the MOS transistor M ₁₄ and the current flowing through the MOS transistor M ₁₅ , both ends of the resistor R ₁₃ are

[0018]

[Equation 4] Voltage is generated. That is, the first term on the right side is the voltage ΔV _BE
Is α times (α = M · R ₁₃ / R ₁₁ ), which is the second side on the right side.
The term is a voltage that is 1 / β of the voltage V _BE1 (β = N · R ₁₂ / R ₁₃ ). here,

[0019]

[Equation 5] _Is selected appropriately, and the change amount of V _BE1 with respect to temperature change,

[0020]

[Equation 6] If the change in temperature is equal to the change in

[0021]

[Equation 7] However, the voltage is almost invariable with temperature. further,

[0022]

[Equation 8] Is selected to be smaller than 1, the reference voltage Vre
f is a temperature-invariant reference voltage of 1.2V or less, 1.2V
The following voltages can be generated accurately.

FIG. 2 shows the voltage ΔV_BEAnd voltage V_BE1Power of
This is an example in which division and addition are performed by voltage. In FIG.
A₁₃~ A₁₇Is an operational amplifier, R₁₄~ R_{twenty four}Is the resistance value
R₁₄~ R_{twenty four}Resistance. Also, the operational amplifier A₁₃and
A₁₄Acts as a buffer. Furthermore, the operational amplifier A
₁₅And resistance R₁₄~ R₁₇Is the voltage V_BE1Resistance R₁₄~ R₁₇Ratio of
According to the voltage A_GIt is an amplifier that is multiplied by -α with respect to
Operational amplifier A₁₆And resistance R ₁₈~ R_{twenty one}Is the voltage ΔV_BEResistance R₁₈
~ R_{twenty one}Voltage A according to the ratio of_GTo -β / 1 /
It is an amplifier. These voltages are the operational amplifier A₁₇And resistance R
_{twenty two}~ R_{twenty four}Is added by the voltage A_GAnd operational amplifier A₁₇
The reference voltage Vref is generated between the output terminal and the output terminal. Obey
And the reference voltage is

[0024]

[Equation 9] Therefore, by determining α and β in the same manner as the ratio of the resistor and the current mirror circuit of FIG. 1, it is possible to obtain a reference voltage that is invariant with temperature.

FIG. 3 shows an example in which the voltage ΔV _BE and the voltage V _BE1 are multiplied / divided by electric charges, which is constituted by a known switched capacitor circuit. In FIG. 3, A ₁₈ is an operational amplifier, and C _{1 to} C ₃ are capacitance values C ₁ to C.
₃ , capacitors S _{1 to} S ₆ are switches which are turned on by the clock φ ₁ , and S _{7 to} S ₁₂ are switches which are turned on by the clock φ ₂ . Further, C ₄ is an integrating capacitor for stabilizing the output of the reference voltage Vref and removing high frequency noise.
The clocks φ ₁ and φ ₂ are non-overlap clocks that do not overlap each other.

Clock φ₁Switch S₁~ S₆
Is turned on, the voltage V_BE1Is equivalent to the capacitance
C₁Stored in the_BEIs equivalent to the capacitance C₂
Stored in. Clock φ₂Switch S₇~ S₁₂
Is turned on, the capacity C ₁Charge and capacity stored in
C₂The charge stored in the capacitor C₃Move to the operational amplifier
A₁₈Voltage A at the output of_GAgainst the reference voltage

[0027]

[Equation 10] Is output. Therefore, by determining C ₁ : C ₃ and C ₂ : C ₃ as described above, it is possible to obtain a reference voltage that is invariant with temperature.

[0028]

According to the present invention, a power supply voltage of 1.2 V or less can be used to generate a reference voltage of 1.2 V or less, which is almost invariable with temperature.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing a reference voltage generating circuit of the present invention.

FIG. 4 is a diagram showing a conventional reference voltage generating circuit.

FIG. 5 is a diagram showing another example of a conventional reference voltage generating circuit.

[Explanation of symbols]

Tr ₁₁ , Tr ₁₂ Bipolar transistor R _{11 to} R ₂₄ Resistance M _{11 to} M ₁₅ MOS transistor A _{11 to} A ₁₈ Operational amplifier C _{1 to} C ₃ Capacitance element S _{1 to} S ₁₂ switch

Claims (1)

[Claims] 1. A first and second bipolar galvanized register-based operating at different current densities - and the voltage [Delta] V _BE of the difference emitter voltage, the first bipolar galvanized register-based - and emitter voltage V _BE In the reference voltage generating circuit for obtaining the reference voltage according to the above, the output voltage is α times the voltage ΔV _BE and 1 / β of the voltage V _BE.
A reference voltage generating circuit characterized by being a sum of voltages (where β> 1).