A bandgap reference source circuit

Abstract

The application discloses a band gap reference source circuit. The band gap reference source circuit generates a current irrelevant to a power supply voltage by utilizing a cross-coupled four-tube unit without using an integrated operational amplifier, introduces the current into a reference voltage generating unit through a current mirror, and makes the reference voltage generating unit generate a reference voltage irrelevant to the power supply voltage and low temperature drift. Meanwhile, a feedback mechanism and a compensation mechanism are introduced by using transistors Q10 and Q5 respectively, and an extra degenerate bias point is eliminated by a bias circuit, so that the output reference voltage is ensured to be in a constant state. The band gap reference source circuit provided by the application has a wide input voltage range, good adaptability to a power supply, constant output voltage, little influence of temperature and input power supply voltage fluctuation, no temperature failure problem of the integrated operational amplifier, simple structure, high reliability and low cost.

Description

Technical Field

[0001] This invention relates to the field of power management for electronic information equipment, and more specifically to a low-temperature drift bandgap reference source circuit without integrated operational amplifiers. Background Technology

[0002] The development of information technology and the Internet of Things (IoT) has not only facilitated people's lives but also driven continuous innovation and progress in integrated circuits, promoting the rapid development of the semiconductor industry. Today, people's lives are inseparable from various electronic products, such as smartwatches, mobile phones, and smart home devices. The performance demands of these electronic products directly lead to increasingly higher performance requirements for the modules of related integrated circuits. Bandgap reference sources, used to provide reference voltages for other modules, are particularly important and are widely used in basic analog circuits such as linear regulators, switching power supplies, high-precision comparators, ADCs, and DACs. The function of a reference voltage source is to output a stable, accurate power supply with a low temperature drift coefficient and strong load resistance, providing a stable and accurate reference voltage for other circuits or systems. Therefore, the performance of the bandgap reference source, to a certain extent, determines the performance of the entire system.

[0003] Existing technologies mainly achieve a low-temperature drift bandgap reference source through the following three methods:

[0004] (1) A reference source with a low temperature drift coefficient is obtained by mutual compensation between diffusion resistor and Zener diode.

[0005] (2) By superimposing a voltage with a positive temperature coefficient onto the base-emitter voltage V of the transistor in an appropriate ratio BE Above, V BE It is a voltage with a negative temperature coefficient (the forward voltage of a PN junction diode has a negative temperature coefficient), which is then canceled out by an integrated operational amplifier with a positive temperature coefficient, thus obtaining a temperature-independent voltage, which is used as a reference voltage.

[0006] (3) Utilize the good characteristics of sub-threshold devices to obtain a reference source with better performance.

[0007] The above three main bandgap reference source circuits have the following drawbacks:

[0008] The reference voltage output of the bandgap reference source obtained by the first implementation method described above has limited accuracy and stability, making it difficult to meet the requirements of modern high-tech electronic products for bandgap reference sources.

[0009] The bandgap reference circuit obtained by the second implementation method described above suffers from an operational amplifier offset voltage, making it difficult to linearly superimpose the positive and negative temperature coefficient voltages. This leads to a deviation between the output voltage of the bandgap reference and the design value. Since the operational amplifier offset voltage is also affected by external temperature changes, this may further increase the temperature drift of the bandgap reference output voltage and reduce its accuracy. To reduce the error caused by operational amplifier offset, the main measures currently adopted can be divided into the following two categories:

[0010] (1) By using large-size input transistors, selecting appropriate overdrive voltages for the input transistors, and designing the layout reasonably, the offset can be controlled to a minimum.

[0011] (2) By changing the transistors in each branch of the circuit to two transistors connected in series, it is possible to... Increasing, and thus reducing, the offset factor of the integrated operational amplifier (op-amp) is beneficial. However, because integrated op-amps contain many transistors, these measures further increase the number of components and the layout area, leading to a more complex circuit structure, increased component losses, unstable output voltage, increased noise, and a larger temperature drift coefficient. Furthermore, the minimum operating voltage of the integrated operational amplifier also limits the minimum input voltage of the bandgap reference circuit.

[0012] The implementation of the third type of bandgap reference source has high requirements for device parameters, manufacturing process, and packaging method, which greatly increases the production cost. Summary of the Invention

[0013] To address the aforementioned shortcomings of existing bandgap reference source circuits, this invention provides a bandgap reference voltage source circuit without operational amplifiers. This bandgap reference voltage source circuit is insensitive to input voltage (the cross-coupled four-transistor circuit connection ensures that the output voltage does not fluctuate with voltage source fluctuations), has stable output voltage, low temperature drift (the negative feedback design ensures that the output reference voltage does not change with temperature), and features a simple structure and high reliability.

[0014] This invention provides a bandgap reference source circuit. The circuit includes: a cross-coupled four-transistor unit, a negative feedback unit, and a reference voltage generation unit. The cross-coupled four-transistor unit generates a current I independent of the supply voltage; the reference voltage generation unit generates a constant reference voltage independent of the supply voltage and temperature, based on the current I, the compensation current generated by the compensation unit, and the negative feedback voltage introduced by the negative feedback unit.

[0015] Furthermore, the bandgap reference source circuit also includes a current mirror. This current mirror is used to replicate the generated current I to the reference voltage generation unit. The current mirror consists of PMOS transistors PM1 and PM2, wherein the sources of PMOS transistors PM1 and PM2 are connected to the power supply VDD, the drain of PMOS transistor PM1 is connected to the input terminal of the reference voltage generation unit, and the drain of PMOS transistor PM2 is connected to the current output terminal of the cross-coupled four-transistor unit.

[0016] Furthermore, the cross-coupled four-transistor unit consists of NPN transistors Q6, Q7, Q8, and Q9, and resistor R3. The emitter of transistor Q8 is grounded, the collector of transistor Q8 is connected to the emitter of transistor Q6, and the base of transistor Q8 is connected to the collector of transistor Q9. The emitter of transistor Q9 is grounded through resistor R3, the collector of transistor Q9 is connected to the emitter of transistor Q7, and the base of transistor Q9 is connected to the collector of transistor Q8. The bases of transistors Q6 and Q7 are both connected to the collector of transistor Q6 and are biased by a current.

[0017] Further, the reference voltage generation unit consists of PNP transistors Q1 and Q2, NPN transistors Q3 and Q4, and resistors R1 and R2. Transistors Q1 and Q2 are identical transistors, forming a current mirror. The base of transistor Q1 is connected to its own collector, and the emitter of transistor Q1 is connected to the emitter of transistor Q2, serving as the input terminal of the reference voltage generation unit, which is connected to the drain of PMOS transistor PM1. The collector of transistor Q3 is connected to the collector of transistor Q1, and the emitter of transistor Q3 is grounded through a voltage divider network formed by resistors R1 and R2 connected in series. The emitter of transistor Q4 is grounded through resistor R2, and the collector of transistor Q4 is connected to the collector of transistor Q2. The base of transistor Q3 is connected to the base of transistor Q4, serving as the reference voltage output terminal.

[0018] Furthermore, the negative feedback unit includes an NPN transistor Q10, with its base connected to the drain of a PMOS transistor PM1, its emitter connected to the base of transistor Q3, and its collector connected to the power supply VDD. The current compensation unit is composed of a PNP transistor Q5, with its base connected to the collector of transistor Q2, its emitter connected to the emitter of transistor Q1, and its collector connected to both the base and collector of transistor Q6. Transistor Q5 acts as a current compensation transistor, compensating for the current flowing into Q3 from the bases of transistors Q1 and Q2, ensuring that the currents flowing through the emitters of Q4 and Q3 are precisely equal.

[0019] The bandgap reference source circuit provided by this invention uses a cross-coupled four-transistor unit to generate a current I independent of the power supply voltage VDD. A reference voltage generation circuit is designed to generate a reference voltage based on this current I, which is independent of the power supply voltage and minimally affected by temperature changes. Corresponding negative feedback units and current compensation branches are designed to ensure the accurate and constant output reference voltage. The bandgap reference source circuit provided by this invention does not have strict requirements on the input power supply voltage, can adapt to different power supplies, and its output voltage remains constant under different input voltages, with almost no change due to temperature fluctuations. The circuit structure is simple, highly reliable, and low in implementation cost. Attached Figure Description

[0020] Figure 1 A circuit diagram of a first embodiment of the bandgap reference source circuit provided by the present invention;

[0021] Figure 2 This is a circuit diagram of a second embodiment of the bias circuit unit of the cross-coupled four-transistor unit in this invention;

[0022] Figure 3 The simulation waveform diagram of the output voltage of the bandgap reference source circuit provided by the present invention as a function of the input power supply voltage in one embodiment is shown. Detailed Implementation

[0023] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0024] like Figure 1 As shown, the bandgap reference circuit provided by the present invention includes: a bias circuit unit, a current mirror, a reference voltage generation unit, a cross-coupled four-transistor unit, and a negative feedback unit.

[0025] The cross-coupled four-transistor unit is composed of NPN transistors Q6, Q7, Q8, and Q9, and resistor R3. The emitter of transistor Q8 is grounded, the collector of transistor Q8 is connected to the emitter of transistor Q6, and the base of transistor Q8 is connected to the collector of transistor Q9. The emitter of transistor Q9 is grounded through resistor R3, the collector of transistor Q9 is connected to the emitter of transistor Q7, and the base of transistor Q9 is connected to the collector of transistor Q8. The bases of transistors Q6 and Q7 are both connected to the collector of transistor Q6 and receive a bias current. The collector of transistor Q7 serves as the current output terminal of the cross-coupled four-transistor unit. The bias current is provided by the leakage current of PMOS transistor PM3.

[0026] The aforementioned cross-coupled four-transistor unit utilizes the absolute temperature obtained from the diode voltage difference of the four cross-coupled BJTs, while transistors Q6, Q7, Q8, and Q9 utilize their own emitter-junction voltage difference. and the current generated by the third resistor R3 :

[0027] (1)

[0028] In equation (1), the emitter area A6 of transistor Q6 is D6 times that of transistor Q8, and the emitter area A9 of transistor Q9 is C9 times that of transistor Q7. The connection relationship of the four transistors ensures that the current flowing through Q6 and Q8 is the same, and the current flowing through transistors Q7 and Q9 is also the same. Therefore, the current and area in the logarithmic relationship become constant values ​​C9D6. It is a positive temperature coefficient current. The emitter-junction voltages of transistors Q6 and Q8 are matched and subtracted in the diode loop. When the power supply voltage changes, the current changes of transistors Q6 and Q8 cancel each other out through the bias bipolar transistor Q5 branch, meaning the circuit is insensitive to the supply voltage. Furthermore, transistors Q6 and Q7 force the collector voltages of transistors Q8 and Q9 to be equal. Therefore, this cross-coupled four-transistor unit is almost unaffected by base width modulation.

[0029] The reference voltage generation unit consists of PNP transistors Q1 and Q2, NPN transistors Q3 and Q4, and resistors R1 and R2. Transistors Q1 and Q2 are identical and form a current mirror. The base of transistor Q1 is connected to its own collector, and the emitter of transistor Q1 is connected to the emitter of transistor Q2, serving as the input terminal of the reference voltage generation unit, which is connected to the drain of PMOS transistor PM1. The collector of transistor Q3 is connected to the collector of transistor Q1, and the emitter of transistor Q3 is grounded through a voltage divider network formed by resistors R1 and R2. The emitter of transistor Q4 is grounded through resistor R2, and the collector of transistor Q4 is connected to the collector of transistor Q2. The base of transistor Q3 is connected to the base of transistor Q4, serving as the reference voltage output terminal. The collectors of transistors Q5 and Q6 are connected.

[0030] The current compensation unit is composed of a PNP transistor Q5. The base of transistor Q5 is connected to the collector of transistor Q2, the emitter of transistor Q5 is connected to the emitter of transistor Q1, and the collector of transistor Q5 is connected to the base and collector of transistor Q6. Transistor Q5 is used to compensate for the current flowing into transistor Q3 from the bases of transistors Q1 and Q2, so that the current flowing through the emitter of transistor Q4 is exactly equal to the current flowing through the emitter of transistor Q3.

[0031] From the circuit connection relationship of the reference voltage generating unit, we can see that:

[0032] Reference voltage Vref: Vref=VBEQ3+((R1+2R2) / R1)VTIn n ;

[0033] The voltage VR1 across resistor R1: VR1 = VBEQ4 - VBEQ3 = VTIn n ;

[0034] Where VBEQ3 is the voltage between the base and emitter of transistor Q3, and VBEQ4 is the voltage between the base and emitter of transistor Q4; both are negative temperature coefficient voltages. VTIn n Vref is the difference between the base-emitter voltages of two bipolar transistors operating at different current densities, and n is the ratio of the current densities flowing through the emitters of transistors Q4 and Q3. VR1 is directly proportional to temperature, and Vref is kept constant by adjusting the resistances of R1 and R2.

[0035] The negative feedback unit (transistor Q10) provides precise and stable bias current for transistors Q3 and Q4, while simultaneously forming negative feedback to maintain a stable output of Vref. The bandgap reference source circuit provided by this invention rationally utilizes feedback and compensation mechanisms, improving output voltage stability and adaptability to input power supplies without requiring integrated operational amplifiers.

[0036] Considering Figure 1 The current method requires the leakage current of PMOS transistor PM3 to provide bias, which is only suitable for special processes and has a narrow range of applications. If the process is changed, the circuit will fail to start. Therefore, the bias circuit can be replaced with... Figure 2 The microcurrent source shown is composed of PMOS transistors PM3 and PM4 and resistor R4.

[0037] Figure 3 The simulation waveform of the output voltage Vref as a function of the input power supply voltage VDD in one embodiment of the bandgap reference source voltage provided by this invention is shown. The horizontal axis represents the input power supply voltage VDD (in volts), and the vertical axis represents the output voltage Vref (in volts) of the bandgap base source circuit. Figure 3 It can be seen that the bandgap reference source circuit begins to operate stably after the input power supply voltage VDD reaches 2V, and the output voltage Vref remains at 1.224V. Thereafter, as long as the MOSFET and resistors in the bandgap reference source circuit do not break down, the output voltage Vref will remain at 1.224V. Therefore, it can be concluded that the bandgap reference source circuit provided by this invention has good power supply adaptability and does not have stringent requirements on the input voltage.

[0038] The embodiments described above are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions cannot cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions provided in this application.

Claims

1. A bandgap reference source circuit, characterized by, The bandgap reference source circuit includes: a cross-coupled four-transistor unit, a current mirror, a current compensation unit, a negative feedback unit, and a reference voltage generation unit. The cross-coupled four-transistor unit consists of NPN transistors Q6, Q7, Q8, Q9 and resistor R3, and is used to generate a current I independent of the power supply voltage. Among them, transistors Q6 and Q7 are two non-cross-connected transistors, the base of transistor Q6 is connected to the base of transistor Q7, and the collector of transistor Q7 serves as the current output terminal of the cross-coupled four-transistor unit. The current mirror is composed of PMOS transistors PM1 and PM2; wherein, the source of PMOS transistors PM1 and PM2 is connected to the power supply VDD, the drain of PMOS transistor PM1 is connected to the input terminal of the reference voltage generation unit, and the drain of PMOS transistor PM2 is connected to the current output terminal of the cross-coupled four-transistor unit. The reference voltage generating unit generates a constant reference voltage independent of the power supply voltage and temperature based on the current I, the compensation current generated by the compensation unit, and the negative feedback voltage introduced by the negative feedback unit. The reference voltage generating unit consists of PNP transistors Q1 and Q2, NPN transistors Q3 and Q4, and resistors R1 and R2. Transistors Q1 and Q2 are identical and form a current mirror. The base of transistor Q1 is connected to its collector. The emitter of transistor Q1 is connected to the emitter of transistor Q2 as the input terminal of the reference voltage generation unit and connected to the drain of PMOS transistor PM1; the collector of transistor Q3 is connected to the collector of transistor Q1, and the emitter of transistor Q3 is grounded through a voltage divider network composed of resistors R1 and R2 connected in series; the emitter of transistor Q4 is grounded through resistor R2, and the collector of transistor Q4 is connected to the collector of transistor Q2; the base of transistor Q3 is connected to the base of transistor Q4 as the reference voltage output terminal. The negative feedback unit includes an NPN transistor Q10, the base of which is connected to the drain of a PMOS transistor PM1, the emitter of which is connected to the base of a transistor Q3, and the collector of which is connected to the power supply VDD. The current compensation unit is composed of a PNP transistor Q5. The base of transistor Q5 is connected to the collector of transistor Q2, the emitter of transistor Q5 is connected to the emitter of transistor Q1, and the collector of transistor Q5 is connected to the base and collector of transistor Q6.

2. The bandgap reference source circuit of claim 1, wherein, In the cross-coupled four-transistor unit, the emitter of transistor Q8 is grounded, the collector of transistor Q8 is connected to the emitter of transistor Q6, and the base of transistor Q8 is connected to the collector of transistor Q9; the emitter of transistor Q9 is grounded through resistor R3, the collector of transistor Q9 is connected to the emitter of transistor Q7, and the base of transistor Q9 is connected to the collector of transistor Q8; the base of transistor Q6 is connected to the base of transistor Q7 and a bias current is applied.

3. The bandgap reference source circuit of claim 2, wherein, The bias current is provided by the leakage current of PMOS transistor PM3.

4. The bandgap reference source circuit of claim 2, wherein, The bias current is provided by a micro-current source consisting of PMOS transistors PM3 and PM4 and resistor R4.

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