Reference voltage circuit

Abstract

This invention provides a reference voltage circuit that reduces the dependence of the reference voltage on manufacturing variations and temperature fluctuations. [Solution] The reference voltage generation unit 2B generates the thermal voltage V of the semiconductor. T A reference voltage V1B proportional to the current amplification factor is generated. The reference voltage generation unit 3B has a transistor M1 and a current source 31B that supplies current to transistor M1, and generates a reference voltage V2B generated by the base-emitter voltage of transistor M1. The reference voltage circuit 1B outputs a voltage obtained by adding the reference voltage V1B and the reference voltage V2B as the reference voltage VREF2. The current source 31B supplies a current to transistor M1 that is proportional to the current amplification factor of transistor M1.

Description

[Technical Field]

[0001] This invention relates to a reference voltage circuit. [Background technology]

[0002] With the rapid advancement of the information and communications society, improving the precision and stability of electronic devices has become a major challenge. To ensure stable operation of the circuits and systems that make up electronic devices, a stable reference voltage circuit is necessary to provide a constant voltage in all environments. Many semiconductor integrated circuits are used in electronic devices. This invention aims to reduce the dependence of the reference voltage on manufacturing variations and temperature fluctuations in reference voltage circuits, which are widely used to constitute a constant voltage source for semiconductor integrated circuits, and to contribute to improving the precision and stability of electronic devices.

[0003] Conventionally, a bandgap type reference voltage circuit, as shown in Figure 5, is known as a reference voltage circuit used in semiconductor integrated circuits (see, for example, Patent Documents 1 and 2). The reference voltage circuit 100 shown in Figure 5 consists of transistors M2 and M3 whose bases are commonly connected to the output terminal T3, transistors M4 and M5 which are current mirrored as active loads to the collectors of transistors M2 and M3, transistor M8 whose base is connected to the connection point between transistors M3 and M5, whose collector is connected to the bases of transistors M2 and M3, and whose emitter is connected to the positive power supply voltage VCC, and resistors R1 and R2 connected in series. Resistor R1 is connected between the emitter of transistor M2 and the emitter of transistor M3. Resistor R2 is connected between the emitter of transistor M2 and the negative power supply voltage GND.

[0004] Furthermore, as shown in Equation 1, the base-emitter voltage V of transistors M2 and M3 BE2 ,V BE3 The difference between the resistance value R1 of resistor R1 and the collector current I of transistor M3 is C3 It is equal to the product of the base-emitter voltages V of transistors M2 and M3. BE2 ,VBE3 is represented by Formula 2 and Formula 3.

[0005] [Math.]]

[0006] [Math.]]

[0007] [Math.]]

[0008] Here, V T is thermal voltage (kT / q), k is Boltzmann constant, T is absolute temperature, q is elementary charge of an electron, I C2 is the collector current of transistor M2, I S is the reverse saturation current of transistor M2, I S ·A M3 / A M2 is the reverse saturation current of transistor M3, A M2 is the emitter-base junction area of transistor M2, A M3 is the emitter-base junction area of transistor M3.

[0009] The reference voltage VREF output to output terminal T3 is obtained by setting the emitter-base junction area ratio of transistors M2 and M3 to A M2 :A M3 =1:N, and setting the emitter-base junction area ratio of transistors M4 and M5 to A M4 :A M5 =1:1, and is represented by Formula 4.

[0010] [Math.]]

[0011] Here, R2 is the resistance value of resistor R2.

[0012] According to equations 1 to 4 above, the reference voltage VREF is expressed by equation 5 below. Note that the emitter-base junction area ratio of transistors M2 and M3 is A. M2 :A M3 The ratio is set to 1:N. Also, the emitter-base junction area ratio of transistors M4 and M5 is A. M4 :A M5 Assuming a ratio of 1:1, the collector current I C2 =Collector current I C3 That is what they say.

[0013]

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[0014] Thermal voltage V T It has a positive temperature coefficient of approximately +0.086 mV / °C. The base-emitter voltage V of transistor M2 BE2 It has a negative temperature coefficient of approximately -2mV / °C. The values ​​of N, R1, and R2 are set so that the temperature characteristics of the first and second terms of Equation 5 cancel each other out. This makes it possible to obtain a reference voltage VREF with reduced temperature dependence. The reference voltage VREF is approximately equal to the bandgap voltage and is called a bandgap type reference voltage circuit.

[0015] However, even if the values ​​of N, R1, and R2 are set so that the temperature characteristics of the first and second terms of Equation 5 cancel each other out, the base-emitter voltage V of transistor M2 remains unchanged. BE2 Due to manufacturing variations, the reference voltage VREF will fluctuate. The base-emitter voltage V BE2 The current amplification factor h FE It fluctuates depending on [something].

[0016] Also, the collector current I of transistor M2 C2 and the base-emitter voltage V BE2 The relationship is as shown in Equation 2. Here, the reverse saturation current I S It is known that this can be expressed by Equation 6 (see, for example, Non-Patent Document 1). The collector current I of transistor M2 C2Since it is expressed in Equation 7, substituting Equations 6 and 7 into Equation 2, the base-emitter voltage V BE2 This is expressed by Equation 8.

[0017]

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[0018]

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[0019]

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[0020] Here, B and C are proportionality constants, m is the temperature dependence coefficient, and E G V is the energy bandwidth. G0 This is a linear approximation of the bandgap voltage at absolute zero.

[0021] The reference voltage VREF is the base-emitter voltage V in the second term of Equation 5. BE2 The temperature characteristics are offset in the first term. However, as shown in Equation 8, the base-emitter voltage V BE2 The temperature dependence of includes a nonlinear third term. The nonlinear component cannot be canceled out by the linear first term of equation 5 alone. Therefore, the temperature characteristics of the reference voltage VREF exhibit an upward-convex curve, with decreases in the high-temperature and low-temperature regions compared to the room-temperature region.

[0022] The reference voltage VREF of the conventional reference voltage circuit 100 described above is the current amplification factor h of the transistor. FE It fluctuates depending on the voltage and exhibits a curvature characteristic that is dependent on temperature changes. Therefore, for reference voltages in applications requiring stable operation and high precision over a wide temperature range, the transistor's current amplification factor h FE There were challenges such as variations due to manufacturing variability and bending characteristics due to temperature changes. [Prior art documents] [Patent Documents]

[0023] [Patent Document 1] Patent No. 6873827 [Patent Document 2] Japanese Patent Publication No. 2017-191557 [Non-patent literature]

[0024] [Non-Patent Document 1] Behzad Razavi, *Design of Analog CMOS Integrated Circuits (Applied Edition)*, Maruzen Publishing, 2003 (see p. 465, Equation 11.8). [Overview of the project] [Problems that the invention aims to solve]

[0025] This invention has been made in view of the circumstances described above, and its objective is to provide a reference voltage circuit that reduces the dependence of the reference voltage on manufacturing variations and temperature fluctuations. [Means for solving the problem]

[0026] To achieve the aforementioned objectives, the reference voltage circuit according to the present invention is characterized by the following [1] to [8]. [1] A first reference voltage generating unit that generates a first reference voltage proportional to the thermal voltage of the semiconductor, The device comprises a first bipolar transistor and a first current source that supplies current to the first bipolar transistor, and a second reference voltage generation unit that generates a second reference voltage generated by the base-emitter voltage of the first bipolar transistor, A reference voltage circuit that outputs a reference voltage obtained by adding the first reference voltage and the second reference voltage, The first current source supplies a current to the first bipolar transistor that is proportional to the current amplification factor of the first bipolar transistor. It is a reference voltage circuit. [2] In the reference voltage circuit described in [1], The first reference voltage generation unit is, A second and third transistor having different emitter-base junction area ratios or aspect ratios, A second current source that supplies current to the second transistor and the third transistor, respectively, A first resistor connected between the emitter or source of the second transistor and the emitter or source of the third transistor, The second transistor, the third transistor, and the second resistor connected in series with the first resistor, It is a reference voltage circuit. [3] In the reference voltage circuit described in [2], The second current source is, A fourth transistor connected in series with the second transistor, The fourth transistor is currently mirrored to a fifth transistor, and the third transistor is connected in series with the third transistor. It is a reference voltage circuit. [4] In the reference voltage circuit described in [1], The first current source is, A sixth bipolar transistor connected in series with the first bipolar transistor, The device includes a constant current circuit that supplies a constant current to the base of the sixth bipolar transistor. It is a reference voltage circuit. [5] In the reference voltage circuit described in [2], The first current source is, A sixth bipolar transistor connected in series with the first bipolar transistor, A seventh transistor whose base or gate is connected to the base or gate of the second and third transistors, and whose collector or drain is connected to the base of the sixth bipolar transistor, The seventh transistor is connected in series with a third resistor, It is a reference voltage circuit. [6] In the reference voltage circuit described in [3], The first current source is, A sixth bipolar transistor connected in series with the first bipolar transistor, The device includes a current mirror circuit that folds back the current flowing through the fourth transistor and supplies it to the base of the sixth bipolar transistor. It is a reference voltage circuit. [7] In the reference voltage circuit described in any one of items [1] to [6], At least one of the aforementioned transistors is composed of a bipolar transistor. It is a reference voltage circuit. [8] In the reference voltage circuit described in any one of items [1] to [6], At least one of the aforementioned transistors is composed of an electrolytic effect transistor. It is a reference voltage circuit. [Effects of the Invention]

[0027] The reference voltage circuit according to the present invention provides a reference voltage circuit that reduces the dependence of the reference voltage on manufacturing variations and temperature fluctuations.

[0028] The present invention has been briefly described above. Furthermore, the details of the present invention will be further clarified by referring to the attached drawings and reading through the embodiments for carrying out the invention described below (hereinafter referred to as "embodiments"). [Brief explanation of the drawing]

[0029] [Figure 1] Figure 1 is a circuit diagram showing a reference voltage circuit in the first embodiment. [Figure 2] Figure 2 is a circuit diagram showing the reference voltage circuit in the second embodiment. [Figure 3] Figure 3 is a circuit diagram showing the reference voltage circuit in the third embodiment. [Figure 4] Figure 4 is a circuit diagram showing the reference voltage circuit in the fourth embodiment. [Figure 5] Figure 5 is a circuit diagram showing an example of a conventional reference voltage circuit. [Modes for carrying out the invention]

[0030] Specific embodiments of the present invention will be described below with reference to the figures.

[0031] (First Embodiment) First, the reference voltage circuit 1 of the first embodiment will be described with reference to Figure 1. As shown in the figure, the reference voltage circuit 1 includes a reference voltage generation unit 2 (= first reference voltage generation unit) that generates a reference voltage V1 (= first reference voltage) and a reference voltage generation unit 3 (= second reference voltage generation unit) that generates a reference voltage V2 (= second reference voltage), and a reference voltage VREF1, which is the sum of the reference voltages V1 and V2, is output from the output terminal T3.

[0032] The reference voltage generation unit 2 comprises a current source 21 and a resistor R10. The current source 21 and resistor R10, connected in series, are connected between the positive power supply terminal T21 and the negative power supply terminal T22. The positive power supply terminal T21 is supplied with a positive power supply voltage VCC, and the negative power supply terminal T22 is supplied with a negative power supply voltage GND.

[0033] The reference voltage generation unit 2 generates a reference voltage V1 generated by the voltage drop across resistor R10. The current I generated by current source 21 21 A thermal voltage V expressed by the following equation 9 T The current is proportional to the thermal voltage V. The reference voltage V1 is given by the thermal voltage V as expressed in equation 10. T The voltage will be proportional to the voltage.

[0034]

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[0035]

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[0036] Here, R 10 V is the resistance value of resistor R10. T is the thermal voltage (kT / q), where k is the Boltzmann constant, T is the absolute temperature, q is the unit charge of an electron, and K G1 V is the thermal voltage T This is a constant that represents the amplification factor.

[0037] The reference voltage generation unit 3 comprises a current source 31 (= first current source) and a transistor M1 (= first bipolar transistor). Transistor M1 is composed of a PNP type bipolar transistor. The current source 31 and transistor M1, connected in series, are connected between the positive power supply terminal T21 and the negative power supply terminal T22. The base of transistor M1 is connected to the connection point between the current source 21 and the resistor R10, and the collector is connected to the negative power supply terminal T22. The output terminal T3 is connected to the connection point between the current source 31 and transistor M1.

[0038] The reference voltage generation unit 3 generates the base-emitter voltage V of transistor M1. BE1 The reference voltage V2 is generated by the current source 31. 31 The current amplification factor h of a transistor is expressed by Equation 11. FE Assuming the current is proportional to the voltage, the reference voltage V2 will be the voltage shown in Equation 12.

[0039]

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[0040]

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[0041] Here, I SThis is the reverse saturation current of transistor M1.

[0042] Reference voltage circuit 1 outputs a voltage from output terminal T3 as reference voltage VREF1, which is the sum of reference voltage V1 and reference voltage V2. Reference voltage VREF1 is expressed by equation 13.

[0043]

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[0044] The reference voltage V1 is generated by the voltage drop across resistor R10, and the thermal voltage V T It is proportional to (+0.086mV / ℃×K) G1 The positive temperature characteristic is approximately ). The reference voltage V2 is the base-emitter voltage V of transistor M1. BE1 Therefore, it exhibits a negative temperature characteristic of approximately -2mV / °C.

[0045] Therefore, as shown in Equation 14, the reference voltage V1 (=K G1 ×V T The ratio of the temperature characteristic of () to the absolute value of the temperature characteristic of the reference voltage V2 is made equal. This makes the base-emitter voltage V of transistor M1, which is the second term of equation 13, equal. BE1 The temperature characteristics of the first term can be offset, thereby reducing the temperature dependence of the reference voltage VREF1.

[0046]

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[0047] However, the base-emitter voltage V of transistor M1 BE1 This includes a nonlinear component, and the first term of Equation 13 alone cannot completely cancel out the temperature characteristics. Therefore, the temperature characteristics of the reference voltage VREF1 are convex upward curved, with the temperature range decreasing more in the high-temperature and low-temperature regions than in the room-temperature region.

[0048] Furthermore, the current I generated by the current source 31 31 However, if the current amplification factor of the transistor is hFE Let's consider the case where the current is constant rather than proportional to it. As shown in Equation 12, the base-emitter voltage V of transistor M1 BE1 This is the reverse saturation current I S It fluctuates due to manufacturing variations. Reverse saturation current I S The current amplification factor h FE It fluctuates depending on the current amplification factor h. Therefore, the reference voltage VREF1 is equal to the current amplification factor h. FE It fluctuates depending on manufacturing variations.

[0049] Next, in the reference voltage VREF1 generated by the reference voltage circuit 1 described above, the current amplification factor h of the transistor FE This section describes how the dependency due to manufacturing variations is reduced.

[0050] Current I generated by current source 31 31 If the current is constant, then the base-emitter voltage V of transistor M1 BE1 The reference voltage V2 is the reverse saturation current I S It fluctuates due to variations in manufacturing.

[0051] Reverse saturation current I S This is expressed in equation 15, and the base width W B It is inversely proportional to the current amplification factor h of a transistor. FE Also, base width W B Because it is inversely proportional, the reverse saturation current I S The current amplification factor h FE It is proportional to.

[0052]

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[0053] Here, A is the emitter-base junction area, D p p is the hole diffusion coefficient. N0 W is the thermal equilibrium concentration of holes in the base. B This is the base width.

[0054] Furthermore, the factors influencing the variation of the reference voltage VREF1 are, for the first term of Equation 13, predominantly the relative variation of each element, which can be suppressed by layout design. However, for the second term of Equation 13, the base-emitter voltage V of transistor M1... BE1 Manufacturing variability is the dominant factor.

[0055] That is, as shown in equations 11 and 12, the current I generated by the current source 31 31 The current amplification factor h of the transistor FE The current is assumed to be proportional to this. This results in the base-emitter voltage V of transistor M1. BE1 The reference voltage V2 is given by the current amplification factor h FE The dependence on manufacturing variations is reduced. Therefore, the dependence on manufacturing variations of the reference voltage VREF1 is also reduced.

[0056] Next, we will explain the operation in which the curvature due to temperature changes is reduced in the reference voltage VREF1 generated by the reference voltage circuit 1 described above.

[0057] Reverse saturation current I of transistor M1 S This is expressed in Equation 16, where the collector current I of transistor M1 C1 This is expressed in Equation 17. Substituting Equations 16 and 17 into Equation 12, we get the base-emitter voltage V of transistor M1. BE1 The temperature dependence of is expressed by equation 18. Current I generated by current source 31 31 If the current is constant, the inclusion of a nonlinear third term results in a curved characteristic where the change increases as the temperature rises, rather than a straight line.

[0058]

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[0059]

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[0060]

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[0061] where B and F are proportional constants, m and n are temperature dependence coefficients, E G is the energy bandwidth, V G0 is the linear approximation value of the band gap voltage at absolute zero.

[0062] The current amplification factor h of a transistor FE is known to be expressed by the relational formula of Equation 19 if the recombination current is sufficiently small. Further, when the current I generated by the current source 31 31 is a current proportional to the current amplification factor h FE , the collector current I of the transistor M1 C1 is expressed by Equation 20.

[0063]

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[0064]

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[0065] where ΔE G is the reduction width resulting from the band gap narrowing effect at the emitter.

[0066] In Equation 20, since the reduction width ΔE resulting from the band gap narrowing effect G and the Boltzmann constant k are constants that do not depend on temperature change, the collector current I of the transistor M1 C1 exhibits an upwardly convex curvature characteristic. The reverse saturation current I S also exhibits an upwardly convex curvature characteristic similarly from Equation 16. Further, the difference between the temperature dependence coefficient n of the collector current I of the transistor M1 in Equation 18 C1 and the temperature dependence coefficient m of the reverse saturation current I S becomes smaller, and the value of the third term also becomes smaller, so the curvature due to temperature change is also reduced.

[0067] That is, as shown in Equation 17, the collector current I of transistor M1 C1 Current amplification factor h FE The current is assumed to be proportional to this. This means that the base-emitter voltage V of transistor M1 is BE1 This also reduces the curvature caused by temperature changes in the reference voltage V2. Consequently, the curvature caused by temperature changes in the reference voltage VREF1 is also reduced.

[0068] In other words, in this first embodiment, the reference voltage circuit 1 adjusts the current source 21 and resistor R10 to a value that makes the ratio of the absolute value of the temperature characteristic of reference voltage V2 to the temperature characteristic of reference voltage V1 equal, thereby obtaining a reference voltage VREF1 with reduced temperature dependence. Also, the current I generated by the current source 31 31 The current amplification factor h of the transistor FE By using a current proportional to the voltage, a reference voltage VREF1 independent of manufacturing variations can be obtained, and curvature due to temperature changes is also reduced.

[0069] Therefore, this method has the effect of reducing the dependence of the reference voltage on manufacturing variations and temperature fluctuations.

[0070] (Second Embodiment) Next, the reference voltage circuit 1B of the second embodiment will be described with reference to Figure 2. As shown in the figure, the reference voltage circuit 1B includes a reference voltage generation unit 2B that generates a reference voltage V1B and a reference voltage generation unit 3B that generates a reference voltage V2B, and a reference voltage VREF2, which is the sum of the reference voltages V1B and V2B, is output from the output terminal T3.

[0071] The reference voltage generation unit 2B comprises transistors M2 (=second transistor), M3 (=third transistor), current source 21B (=second current source), resistor R1 (=first resistor), resistor R2 (=second resistor), and transistor M8. Transistors M2 and M3 are composed of NPN bipolar transistors.

[0072] Transistors M2 and M3 have different emitter-base junction area ratios. Current source 21B supplies current to transistors M2 and M3, respectively. Current source 21B has transistors M4 (=4th transistor) and M5 (=5th transistor). Transistors M4 and M5 are made up of PNP type bipolar transistors.

[0073] Transistor M4 is connected in series with transistor M2. Specifically, the collector and base of transistor M4 are connected to the collector of transistor M2, and the emitter is connected to the positive power supply terminal T21. Transistor M5 is current mirrored to transistor M4 and connected in series with transistor M3. Specifically, the collector of transistor M5 is connected to the collector of transistor M3, the emitter is connected to the positive power supply terminal T21, and the base is connected to the base and collector of transistor M4.

[0074] Resistor R1 is connected between the emitter of transistor M2 and the emitter of transistor M3. Resistor R2 is connected between the emitter of transistor M2 and the connection point of resistor R1 and the negative power supply terminal T22. Resistor R2 is connected in series with resistor R1. Transistor M8 has its emitter connected to the positive power supply terminal T21, its base connected to the connection point of transistors M3 and M5, and its collector connected to the bases of transistors M2 and M3.

[0075] The reference voltage V1B is expressed by the following equation 21.

[0076]

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[0077] Here, R1 is the resistance value of resistor R1, R2 is the resistance value of resistor R2, I C2 The collector current of transistor M2 is I. C3 This is the collector current of transistor M3.

[0078] According to equations 1 to 3 and 21 above, the reference voltage V1B is expressed by equations 22 and 23 below. Note that the emitter-base junction area ratio of transistors M2 and M3 is A. M2 :A M3 The ratio is set to 1:N. Also, the emitter-base junction area ratio of transistors M4 and M5 is A. M4 :A M5 Assuming a ratio of 1:1, the collector current I C2 =Collector current I C3 That is what they say.

[0079]

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[0080]

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[0081] Here, K G2 V is the thermal voltage T This is a constant that represents the amplification factor.

[0082] The reference voltage generation unit 3B includes a transistor M1 and a current source 31B (= first current source).

[0083] Transistor M1 has its collector connected to the negative power supply terminal T22 and its base connected to the connection point between the emitter of transistor M3 and resistor R1. Current source 31B has transistor M6 (=6th bipolar transistor) and constant current circuit 311. Transistor M6 has its emitter connected to the positive power supply terminal T21 and its collector connected to the emitter of transistor M1. Output terminal T3 is connected to the connection point between the collector of transistor M6 and the emitter of transistor M1.

[0084] Base current I of transistor M6 B6 This is driven by a constant current circuit 311 connected between the base of transistor M6 and the negative power supply terminal T22, and the collector current I of transistor M1 C1 This is expressed by Equation 24.

[0085] The reference voltage generation unit 3B uses the current amplification factor h of the transistor. FE The collector current I of transistor M6 is proportional to the collector current I C6 (See Equation 24) and the base-emitter voltage V of transistor M1. BE1 This generates a reference voltage V2B. The reference voltage V2B is expressed by Equation 25.

[0086]

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[0087]

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[0088] Here, I 31 This is the current generated by the constant current circuit 311.

[0089] Reference voltage circuit 1B outputs a reference voltage VREF2 from output terminal T3, which is the sum of reference voltages V1B and V2B. Reference voltage VREF2 is expressed by equation 26.

[0090]

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[0091] The reference voltage V1B is set by the emitter-base junction area ratio of transistors M2 and M3 and the resistance ratio of resistors R1 and R2, and the thermal voltage V T It is proportional to (+0.086mV / ℃×K) G2 The positive temperature characteristic is approximately ). The reference voltage V2B is the base-emitter voltage V of transistor M1. BE1 Therefore, it exhibits a negative temperature characteristic of approximately -2mV / °C.

[0092] Therefore, as shown in Equation 27, the reference voltage V1B(=K G2 ×V TThe ratio of the temperature characteristic of () to the absolute value of the temperature characteristic of the reference voltage V2B is made equal. This makes the base-emitter voltage V of transistor M1, which is the second term of equation 26, equal. BE1 The temperature characteristics of the first term can be offset, thereby reducing the temperature dependence of the reference voltage VREF2.

[0093]

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[0094] However, the base-emitter voltage V of transistor M1 BE1 Since it includes a nonlinear component, and the first term of Equation 26 alone cannot completely cancel out the temperature characteristics, the temperature characteristics of the reference voltage VREF2 have an upward-convex curved shape, with the high-temperature and low-temperature regions being lower than the room-temperature region.

[0095] Also, the collector current I of transistor M1 C1 However, if the current amplification factor h FE Let's consider the case where the current is constant rather than proportional to it. As shown in Equation 25, the base-emitter voltage V of transistor M1 BE1 This is the reverse saturation current I S It fluctuates due to manufacturing variations. Reverse saturation current I S The current amplification factor h FE Because it fluctuates depending on the current amplification factor h, the reference voltage VREF2 is FE It fluctuates depending on manufacturing variations.

[0096] Next, in the reference voltage VREF2 generated by the reference voltage circuit 1B described above, the current amplification factor h of the transistor FE This section describes how the dependency due to manufacturing variations is reduced.

[0097] The collector current I of transistor M1 C1 If the current is constant, then the base-emitter voltage V of transistor M1 BE1 The reference voltage V2B is the reverse saturation current I S It fluctuates due to variations in manufacturing.

[0098] Reverse saturation current I S This is expressed in equation 15, and the base width W B It is inversely proportional to the current amplification factor h of a transistor. FE Also, base width W B Because it is inversely proportional, the reverse saturation current I S The current amplification factor h FE It is proportional to.

[0099] Furthermore, the factors influencing the fluctuation of the reference voltage VREF2 are, for the first term of Equation 26, predominantly the relative variation of each element, which can be suppressed by layout design, but for the second term of Equation 26, the base-emitter voltage V of transistor M1... BE1 Manufacturing variability is the dominant factor.

[0100] That is, as shown in equations 24 and 25, the collector current I of transistor M1 C1 Current amplification factor h FE The current is assumed to be proportional to this. This results in the base-emitter voltage V of transistor M1. BE1 The reference voltage V2B is given by the current amplification factor h FE The dependence on manufacturing variations is reduced. Therefore, the dependence on manufacturing variations of the reference voltage VREF2 is also reduced.

[0101] Next, we will explain the operation in which the curvature due to temperature changes is reduced in the reference voltage VREF2 generated by the reference voltage circuit 1B described above.

[0102] Reverse saturation current I of transistor M1 S This is expressed by Equation 16. The collector current I of transistor M1 C1 This is expressed in equation 28. Substituting equations 16 and 28 into equation 25, we get the base-emitter voltage V of transistor M1. BE1 The temperature dependence is given by equation 29. The collector current I of transistor M1 C1 If the current is constant, the inclusion of a nonlinear third term results in a curved characteristic where the change increases as the temperature rises, rather than a straight line.

[0103]

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[0104]

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[0105] Transistor current amplification factor h FE It is known that if the recombination current is sufficiently small, it can be expressed by the relationship in Equation 19. Also, the base current I of transistor M6 B6 If we assume that is a constant current independent of temperature changes, then the collector current I of transistor M1 C1 This is expressed by equation 20.

[0106] In Equation 20, the reduction in band gap due to the band gap reduction effect ΔE G And since the Boltzmann constant k is a constant that does not depend on temperature changes, the collector current I of transistor M1 C1 The curve has an upward convex curvature characteristic. Reverse saturation current I S Similarly, from equation 16, the curved characteristic is convex upwards. Also, the collector current I of transistor M1 in equation 29 C1 The temperature-dependent coefficient n and the reverse saturation current I S As the difference between the temperature dependence coefficient m and the third term decreases, the curvature due to temperature changes is also reduced.

[0107] That is, as shown in Equation 28, the collector current I of transistor M1 C1 Current amplification factor h FE By making the current proportional to the base-emitter voltage V of transistor M1, BE1 This also reduces the curvature of the reference voltage V2B due to temperature changes. Consequently, the curvature of the reference voltage VREF2 due to temperature changes is also reduced.

[0108] In other words, in this second embodiment, the reference voltage circuit 1B adjusts the emitter-base junction area ratio of transistors M2 and M3 and the resistance ratio of resistors R1 and R2 to a value that makes the ratio of the absolute value of the temperature characteristic of reference voltage V2B to the temperature characteristic of reference voltage V1B equal, thereby obtaining a reference voltage VREF2 with reduced temperature dependence. Also, the collector current I of transistor M1 C1 Current amplification factor h FE By using a current proportional to the voltage, a reference voltage VREF2 independent of manufacturing variations can be obtained, and the curvature due to temperature changes is also reduced.

[0109] Therefore, this method has the effect of reducing the dependence of the reference voltage on manufacturing variations and temperature fluctuations.

[0110] (Third embodiment) Next, the reference voltage circuit 1C of the third embodiment will be described with reference to Figure 3. In Figure 3, components that are the same as those in the circuit shown in Figure 2 are given the same reference numerals, and their detailed descriptions are omitted.

[0111] As shown in the figure, the reference voltage circuit 1C, similar to the second embodiment, includes a reference voltage generation unit 2B that generates a reference voltage V1B and a reference voltage generation unit 3C that generates a reference voltage V2C, and a reference voltage VREF3, which is the sum of the reference voltages V1B and V2C, is output from the output terminal T3. The reference voltage generation unit 2B is the same as in the second embodiment described above, so a detailed explanation is omitted here.

[0112] The difference between the second and third embodiments lies in the configuration of the reference voltage generation unit 3C. The reference voltage generation unit 3C comprises a transistor M1 and a current source 31C (= first current source).

[0113] Transistor M1 has its collector connected to the negative power supply terminal T22, and its base connected to the connection point between the emitter of transistor M3 and resistor R1. The current source 31C has transistors M6 and M7, and resistor R3. Transistor M6 is a PNP type bipolar transistor, and transistor M7 is an NPN type bipolar transistor.

[0114] Transistor M6 has its emitter connected to the positive power supply terminal T21 and its collector connected to the emitter of transistor M1. Output terminal T3 is connected to the connection point between the collector of transistor M7 and the emitter of transistor M1.

[0115] Transistor M7 has its collector connected to the base of transistor M6, its base connected to the connection point (junction node A) between the bases of transistors M2 and M3 and the collector of transistor M8, and its emitter connected to the negative power supply terminal T22 via resistor R3. The voltage at junction node A is V A This is expressed by equation 30.

[0116] Base current I of transistor M6 B6 This is driven by a constant current circuit consisting of transistor M7 and resistor R3, and is represented by equation 31. Furthermore, by using a resistor R3 with a temperature coefficient of approximately +2000 to 3000 ppm / °C, a constant current with suppressed temperature dependence is generated.

[0117]

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[0118]

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[0119] Here, R3 is the resistance value of resistor R3.

[0120] The reference voltage generation unit 3C has a transistor current amplification factor h FEThe collector current I of transistor M6 is proportional to the collector current I C6 (See Equation 32) and the base-emitter voltage V of transistor M1 BE1 This generates a reference voltage V2C. The reference voltage V2C is expressed by Equation 33.

[0121]

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[0122]

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[0123] The reference voltage circuit 1C outputs a reference voltage VREF3 from output terminal T3, which is the sum of reference voltages V1B and V2C. The reference voltage VREF3 is expressed by equation 34.

[0124]

number

[0125] The reference voltage V1B is set by the emitter-base junction area ratio of transistors M2 and M3 and the resistance ratio of resistors R1 and R2, and the thermal voltage V T It is proportional to (+0.086mV / ℃×K) G2 The temperature characteristics will be approximately ). The reference voltage V2C is the base-emitter voltage V of transistor M1. BE1 Therefore, it exhibits a negative temperature characteristic of approximately -2mV / °C.

[0126] Therefore, as shown in Equation 27, the reference voltage V1B(=K G2 ×V T By making the ratio of the temperature characteristics of () and the absolute value of the temperature characteristics of the reference voltage V2C equal, the base-emitter voltage V of transistor M1, which is the second term of equation 34, becomes BE1 The temperature characteristics of the first term can be offset, thereby reducing the temperature dependence of the reference voltage VREF3.

[0127] However, the base-emitter voltage V of transistor M1 BE1 Since it includes a nonlinear component, and the first term of Equation 34 alone cannot completely cancel out the temperature characteristics, the temperature characteristics of the reference voltage VREF3 are convex upward curved, with the high-temperature and low-temperature regions being lower than the room-temperature region.

[0128] Also, the collector current I of transistor M1 C1 However, if the current amplification factor h FE Let's consider the case where the current is constant rather than proportional to it. As shown in Equation 33, the base-emitter voltage V of transistor M1 BE1 This is the reverse saturation current I S It fluctuates due to manufacturing variations. Reverse saturation current I S The current amplification factor h FE Because it fluctuates depending on the current amplification factor h, the reference voltage VREF3 is FE It fluctuates depending on manufacturing variations.

[0129] Next, in the reference voltage VREF3 generated by the reference voltage circuit 1C described above, the current amplification factor h of the transistor FE This section describes how the dependency due to manufacturing variations is reduced.

[0130] The collector current I of transistor M1 C1 If the current is constant, then the base-emitter voltage V of transistor M1 BE1 The reference voltage V2C is the reverse saturation current I S It fluctuates due to variations in manufacturing.

[0131] Reverse saturation current I S This is expressed in equation 15, and the base width W B It is inversely proportional to the current amplification factor h of a transistor. FE Also, base width W B Because it is inversely proportional, the reverse saturation current I S The current amplification factor h FE It is proportional to.

[0132] Further, regarding the factors causing variation in the reference voltage VREF3, for the first term of Equation 34, relative variation between elements is dominant and can be suppressed by means such as layout design, but for the second term of Equation 34, the base-emitter voltage V of the transistor M1 BE1 manufacturing variation is dominant.

[0133] That is, as shown in Equations 32 and 33, by setting the collector current I of the transistor M1 C1 to be a current proportional to the current amplification factor h FE , the dependence of the reference voltage V2C, which is the base-emitter voltage V of the transistor M1 BE1 , on manufacturing variation of the current amplification factor h FE is reduced. Accordingly, the dependence of the reference voltage VREF3 on manufacturing variation is also reduced.

[0134] Next, the operation for reducing curvature due to temperature change in the reference voltage VREF3 generated by the above-described reference voltage circuit 1C will be described.

[0135] The reverse saturation current I of the transistor M1 S is expressed by Equation 16, and the collector current I of the transistor M1 C1 is expressed by Equation 35. Therefore, when Equations 16 and 35 are substituted into Equation 33, the temperature dependence of the base-emitter voltage V of the transistor M1 BE1 is expressed by Equation 36. If the collector current I of the transistor M1 C1 is a constant current, the inclusion of the non-linear third term results in a curved characteristic that is not linear, where the change becomes larger as temperature increases.

[0136] ##

[0137] ##

[0138] The current amplification factor h of the transistor FEIt is known that if the recombination current is sufficiently small, it can be expressed by the relationship in Equation 19. Also, the base current I of transistor M6 B6 If we assume that is a constant current independent of temperature changes, then the collector current I of transistor M1 C1 This is expressed by equation 20.

[0139] In Equation 20, the reduction in band gap due to the band gap reduction effect ΔE G And since the Boltzmann constant k is a constant that does not depend on temperature changes, the collector current I of transistor M1 C1 The curve has an upward convex curvature characteristic. Reverse saturation current I S Similarly, from equation 16, the curved characteristic is convex upwards. Also, the collector current I of transistor M1 in equation 36 C1 The temperature-dependent coefficient n and the reverse saturation current I S As the difference between the temperature dependence coefficient m and the third term decreases, the curvature due to temperature changes is also reduced.

[0140] That is, as shown in Equation 35, the collector current I of transistor M1 C1 Current amplification factor h FE By making the current proportional to the base-emitter voltage V of transistor M1, BE1 This also reduces the curvature caused by temperature changes in the reference voltage V2C. Consequently, the curvature caused by temperature changes in the reference voltage VREF3 is also reduced.

[0141] In other words, in this third embodiment, the reference voltage circuit 1C adjusts the emitter-base junction area ratio of transistors M2 and M3 and the resistance ratio of resistors R1 and R2 to a value that makes the ratio of the absolute value of the temperature characteristic of reference voltage V2C to the temperature characteristic of reference voltage V1B equal, thereby obtaining a reference voltage VREF3 with reduced temperature dependence. Also, the collector current I of transistor M1 C1 Current amplification factor h FE By using a current proportional to the voltage, a reference voltage VREF3 independent of manufacturing variations can be obtained, and the curvature due to temperature changes is also reduced.

[0142] Therefore, this method has the effect of reducing the dependence of the reference voltage on manufacturing variations and temperature fluctuations.

[0143] (Fourth Embodiment) Next, the reference voltage circuit 1D of the fourth embodiment will be described with reference to Figure 4. In Figure 4, components identical to those in the circuit shown in Figure 2 are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0144] As shown in the figure, the reference voltage circuit 1D, similar to the second embodiment, includes a reference voltage generation unit 2B that generates a reference voltage V1B and a reference voltage generation unit 3D that generates a reference voltage V2D, and the voltage VREF4, which is the sum of the reference voltages V1B and V2D, is output from the output terminal T3. The reference voltage generation unit 2B is the same as in the second embodiment described above, so a detailed explanation is omitted here.

[0145] The difference between the second and fourth embodiments lies in the configuration of the reference voltage generation unit 3D. The reference voltage generation unit 3D comprises a transistor M6 and a current mirror circuit 312. The emitter of transistor M6 is connected to the positive power supply terminal T21, and the collector is connected to the emitter of transistor M1. Transistor M6 is connected in series with transistor M1. The current mirror circuit 312 folds back the current flowing through transistor M4 and supplies it to the base of transistor M6.

[0146] The current mirror circuit 312 includes transistors M9, M10, and M11. Transistors M10 and M11 are NPN bipolar transistors. Transistor M9 is a PNP bipolar transistor.

[0147] Transistor M9 has its emitter connected to the positive power supply terminal T21, and its base connected to the base and collector of transistor M4. In other words, transistor M9 is current-mirror connected to transistor M4, copying and folding back the current flowing through transistor M4. Transistor M10 has its base and collector connected to the collector of transistor M9, and its emitter connected to the negative power supply terminal T22. Transistors M9 and M10 are connected in series. Transistor M11 has its base connected to the base and collector of transistor M10, its emitter connected to the negative power supply terminal T22, and its collector connected to the base of transistor M6. In other words, transistor M11 is current-mirror connected to transistor M10, copying and folding back the current flowing through transistor M10 and supplying it to the base of transistor M6.

[0148] Base current I of transistor M6 B6 This is the collector current I of transistor M4. C4 A current proportional to this flows, and the emitter-base junction area ratio of transistors M4 and M9 is A M4 :A M9 =1:1, the emitter-base junction area ratio of transistors M10 and M11 is A M10 :A M11 If we set =M:1, it is expressed in equation 37. Also, the base current I of transistor M6 B6 The resistor R1 is connected to the thermal voltage V of the semiconductor. T By using a resistor with a temperature coefficient of approximately +3300 ppm / °C, which is equal to the temperature coefficient of [the specified value], a constant current with suppressed temperature dependence can be generated.

[0149]

number

[0150] Here, M is the emitter-base junction area ratio of transistors M10 and M11 (A M10 / A M11 ), A M10 This is the emitter-base junction area of ​​transistor M10, A M11is the emitter-base junction area of transistor M11.

[0151] The reference voltage generating unit 3D has a current amplification factor h of the transistor FE the collector current I of transistor M6 proportional to C6 (see formula 38) and the base-emitter voltage V of transistor M1 BE1 generates the reference voltage V2D generated thereby. The reference voltage V2D is represented by formula 39.

[0152] [Mathematical Expression]

[0153] [Mathematical Expression]

[0154] In the reference voltage circuit 1D, a voltage obtained by adding the reference voltage V1B and the reference voltage V2D is output from the output terminal T3 as the reference voltage VREF4. The reference voltage VREF4 is represented by formula 40.

[0155] [Mathematical Expression]

[0156] The reference voltage V1B is set by the emitter-base junction area ratio of transistors M2 and M3 and the resistance ratio of resistors R1 and R2, and the thermal voltage V T is proportional to G2 ), and has a positive temperature characteristic of approximately this level. Since the reference voltage V2D corresponds to the base-emitter voltage V of the transistor M1 BE1 , it has a negative temperature characteristic of approximately -2mV / °C.

[0157] Therefore, as shown in formula 27, the reference voltage V1B (=K G2 ×V TBy making the ratio of the temperature characteristics of () and the absolute value of the temperature characteristics of the reference voltage V2D equal, the base-emitter voltage V of transistor M1, which is the second term of equation 40, becomes BE1 The temperature characteristics of the first term can be offset, thereby reducing the temperature dependence of the reference voltage VREF4.

[0158] However, the base-emitter voltage V of transistor M1 BE1 Since it includes a nonlinear component, and the first term of Equation 40 alone cannot completely cancel out the temperature characteristics, the temperature characteristics of the reference voltage VREF4 will have an upward-convex curved shape, with the temperature decreasing in the high-temperature and low-temperature regions compared to the room-temperature region.

[0159] Also, the collector current I of transistor M1 C1 However, if the current amplification factor h FE Let's consider the case where the current is constant rather than proportional to it. As shown in Equation 39, the base-emitter voltage V of transistor M1 BE1 This is the reverse saturation current I S It fluctuates due to manufacturing variations. Reverse saturation current I S The current amplification factor h FE Because it fluctuates depending on the current amplification factor h, the reference voltage VREF4 is FE It fluctuates depending on manufacturing variations.

[0160] Next, in the reference voltage VREF4 generated by the reference voltage circuit 1D described above, the current amplification factor h of the transistor FE This section describes how the dependency due to manufacturing variations is reduced.

[0161] The collector current I of transistor M1 C1 If the current is constant, then the base-emitter voltage V of transistor M1 BE1 The reference voltage V2D is the reverse saturation current I S It fluctuates due to variations in manufacturing.

[0162] Reverse saturation current I S This is expressed in equation 15, and the base width W B It is inversely proportional to the current amplification factor h of a transistor.FE Also, base width W B Because it is inversely proportional, the reverse saturation current I S The current amplification factor h FE It is proportional to.

[0163] Furthermore, the factors causing fluctuations in the reference voltage VREF4 are, for the first term of Equation 40, predominantly the relative variation of each element, which can be suppressed by layout design, but for the second term of Equation 40, the base-emitter voltage V of transistor M1... BE1 Manufacturing variability is the dominant factor.

[0164] That is, as shown in equations 38 and 39, the collector current I of transistor M1 C1 Current amplification factor h FE By making the current proportional to the base-emitter voltage V of transistor M1, BE1 The reference voltage V2D is given by the current amplification factor h FE The dependence due to manufacturing variations is reduced. Therefore, the dependence of the reference voltage VREF4 due to manufacturing variations is also reduced.

[0165] Next, we will explain the operation in which the curvature due to temperature changes is reduced in the reference voltage VREF4 generated by the reference voltage circuit 1D described above.

[0166] Reverse saturation current I of transistor M1 S This is expressed in Equation 16, where the collector current I of transistor M1 C1 Since this is expressed in equation 41, substituting equations 16 and 41 into equation 39, the base-emitter voltage V of transistor M1 is obtained. BE1 The temperature dependence is given by equation 42. The collector current I of transistor M1 C1 If the current is constant, the inclusion of a nonlinear third term results in a curved characteristic where the change increases as the temperature rises, rather than a straight line.

[0167]

number

[0168]

number

[0169] Transistor current amplification factor h FE It is known that if the recombination current is sufficiently small, it can be expressed by the relationship in Equation 19. Also, the base current I of transistor M6 B6 If we assume that is a constant current independent of temperature changes, then the collector current I of transistor M1 C1 This is expressed by equation 20.

[0170] In Equation 20, the reduction in band gap due to the band gap reduction effect ΔE G And since the Boltzmann constant k is a constant that does not depend on temperature changes, the collector current I of transistor M1 C1 The curve has an upward convex curvature characteristic. Reverse saturation current I S Similarly, from equation 16, the curved characteristic is convex upwards. Also, the collector current I of transistor M1 in equation 42 C1 The temperature-dependent coefficient n and the reverse saturation current I S As the difference between the temperature dependence coefficient m and the third term decreases, the curvature due to temperature changes is also reduced.

[0171] That is, as shown in Equation 41, the collector current I of transistor M1 C1 Current amplification factor h FE By making the current proportional to the base-emitter voltage V of transistor M1, BE1 This also reduces the curvature of the reference voltage V2D due to temperature changes. Consequently, the curvature of the reference voltage VREF4 due to temperature changes is also reduced.

[0172] In other words, in this fourth embodiment, the reference voltage circuit 1D adjusts the emitter-base junction area ratio of transistors M2 and M3 and the resistance ratio of resistors R1 and R2 to a value that makes the ratio of the absolute value of the temperature characteristic of reference voltage V2D to the temperature characteristic of reference voltage V1B equal, thereby obtaining a reference voltage VREF4 with reduced temperature dependence. Also, the collector current I of transistor M1 C1 Current amplification factor h FEBy using a current proportional to the voltage, a reference voltage VREF4 independent of manufacturing variations can be obtained, and the curvature due to temperature changes is also reduced.

[0173] Therefore, this method has the effect of reducing the dependence of the reference voltage on manufacturing variations and temperature fluctuations.

[0174] (Other embodiments) The present invention is not limited to the embodiments described above, and can be modified, improved, etc., as appropriate. Furthermore, the material, shape, dimensions, number, placement, etc., of each component in the embodiments described above are arbitrary and not limited, as long as they can achieve the present invention.

[0175] For example, in the second to fourth embodiments described above, the transistors were composed of bipolar transistors, but the invention is not limited to this. At least one of the transistors, excluding transistors M1 and M6, may be replaced with field-effect transistors. In this case, "PNP type" can be read as "P channel," "NPN type" as "N channel," "base" as "gate," "emitter" as "source," "collector" as "drain," and "emitter-base junction area ratio" as "aspect ratio."

[0176] In the second to fourth embodiments described above, the base of transistor M1 was connected to the connection point between the emitter of transistor M3 and resistor R1, but this is not the only option. It may also be connected to the connection point between resistor R1 and resistor R2.

[0177] Furthermore, while the second to fourth embodiments described above used a reference voltage generation unit 2B as shown in Figures 2 to 4, the invention is not limited to this. Thermal voltage V T Other embodiments are possible as long as the circuit generates a voltage proportional to the given value.

[0178] Furthermore, while the third and fourth embodiments described above used reference voltage generators 3C and 3D as shown in Figures 3 and 4, the invention is not limited to these. Transistor current amplification factor h FE Other embodiments are possible as long as the circuit generates a current proportional to the given value. [Explanation of symbols]

[0179] 1,1B~1D Reference Voltage Circuit 2.2B Reference voltage generation unit (first reference voltage generation unit) 3,3B~3D Reference voltage generation unit (second reference voltage generation unit) 21B Current source (second current source) 31, 31B~31D Current source (first current source) 311 Constant current circuit 312 Current Mirror Circuit M1 transistor (first bipolar transistor) M2 transistor (second transistor) M3 transistor (third transistor) M4 transistor (fourth transistor) M5 transistor (the fifth transistor) M6 transistor (6th bipolar transistor) M7 transistor (the seventh transistor) R1 Resistor (First resistor) R2 Resistor (Second resistor) R3 Resistor (Third resistor) V1, V1B Reference voltage (first reference voltage) V2, V2B~V2D Reference voltage (second reference voltage) VREF1~VREF4 Reference Voltage

Claims

1. A first reference voltage generating unit that generates a first reference voltage proportional to the thermal voltage of the semiconductor, The device comprises a first bipolar transistor and a first current source that supplies current to the first bipolar transistor, and a second reference voltage generation unit that generates a second reference voltage generated by the base-emitter voltage of the first bipolar transistor, A reference voltage circuit that outputs a reference voltage obtained by adding the first reference voltage and the second reference voltage, The first current source supplies the first bipolar transistor with a current proportional to the current amplification factor of the first bipolar transistor. Reference voltage circuit.

2. In the reference voltage circuit described in claim 1, The first reference voltage generating unit is: A second transistor and a third transistor having different emitter-base junction area ratios or aspect ratios, A second current source that supplies current to the second transistor and the third transistor, respectively, A first resistor connected between the emitter or source of the second transistor and the emitter or source of the third transistor, The second transistor, the third transistor, and the second resistor connected in series with the first resistor, Reference voltage circuit.

3. In the reference voltage circuit described in claim 2, The second current source is, A fourth transistor connected in series with the second transistor, The fourth transistor is connected to the third transistor via a current mirror, and the fifth transistor is connected to the third transistor via a series, Reference voltage circuit.

4. In the reference voltage circuit described in claim 1, The first current source is, A sixth bipolar transistor connected in series with the first bipolar transistor, The device includes a constant current circuit that supplies a constant current to the base of the sixth bipolar transistor. Reference voltage circuit.

5. In the reference voltage circuit described in claim 2, The first current source is, A sixth bipolar transistor connected in series with the first bipolar transistor, A seventh transistor whose base or gate is connected to the base or gate of the second and third transistors, and whose collector or drain is connected to the base of the sixth bipolar transistor, The seventh transistor is connected in series with a third resistor, Reference voltage circuit.

6. In the reference voltage circuit described in claim 3, The first current source is, A sixth bipolar transistor connected in series with the first bipolar transistor, The device includes a current mirror circuit that folds back the current flowing through the fourth transistor and supplies it to the base of the sixth bipolar transistor. Reference voltage circuit.

7. In the reference voltage circuit according to any one of claims 1 to 6, At least one of the aforementioned transistors is composed of a bipolar transistor. Reference voltage circuit.

8. In the reference voltage circuit according to any one of claims 1 to 6, At least one of the aforementioned transistors is composed of an electrolytic effect transistor. Reference voltage circuit.

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