Low voltage integrated circuit operational amplifier

Abstract

The utility model relates to an analog integrated circuit. The utility model discloses a low-voltage integrated circuit operational amplifier, and aims to solve the problem of higher working voltage of an operational amplifier in the prior art by improving a circuit structure and reducing the number of inter-electrode voltage drops of transistors of a direct current channel of the amplifier. The low-voltage integrated circuit operational amplifier comprises a multi-stage amplifier formed by transistors, and is characterized in that a direct current channel of the amplifier only comprises a transistor base-emitter voltage drop. According to the integrated circuit operational amplifier, the number of inter-electrode voltage drops of transistors of a direct-current channel of the amplifier is reduced by improving the circuit structure, and the integrated circuit operational amplifier has the characteristics of low power consumption and high gain while meeting low-voltage work and can be applied to systems such as power management, portable equipment, sensors and communication equipment.

Description

Technical Field

[0001] The present application relates to the field of integrated circuit technology, in particular to analog integrated circuits, and more specifically to low-voltage integrated circuit operational amplifiers. Background Art

[0002] While maintaining the high bandwidth, high speed, low distortion and other performance requirements of electronic systems, improving energy efficiency has always been one of the hot research directions of integrated circuits.

[0003] However, in the field of integrated circuit design, high bandwidth and high speed characteristics are positively correlated with the operating current of its transistors, which is also directly related to higher energy consumption. Therefore, reducing the system operating voltage is an important way to reduce system power consumption and improve energy efficiency.

[0004] Operational amplifiers (OPA) are the cornerstone of analog integrated circuits and are used in a variety of electronic systems. To reduce system energy consumption, the operating voltage of electronic systems is gradually decreasing, and the operating voltage of IC operational amplifiers is also decreasing accordingly. To ensure proper system operation, research on how to operate operational amplifiers under ultra-low voltage conditions is a key topic in this field.

[0005] The operating voltage of an op amp is affected by its circuit structure and process. For the same circuit structure, the smaller the diode forward voltage drop or the lower the MOS transistor threshold voltage, the lower the op amp's minimum operating voltage. For example, the forward voltage drop of a diode designed using a germanium process can be as low as 0.3V, making the operating voltage of an op amp designed using a germanium process much lower than that of an op amp designed using a silicon process. However, the germanium process is expensive, making it suitable for circuit design in only a few applications. Once the process is determined, improving the circuit structure becomes the only way to reduce the op amp's operating voltage.

[0006] The circuit structure of the prior art integrated circuit operational amplifier has some areas that need to be improved. The main problem is that the multi-stage amplifier in the integrated circuit operational amplifier usually contains multiple transistor inter-electrode voltage drops in its DC channel, especially the transistor base-emitter / collector voltage drop, which leads to a high operating voltage of the entire operational amplifier. Summary of the Invention

[0007] The main purpose of this application is to provide a low-voltage integrated circuit operational amplifier, which reduces the number of transistor inter-electrode voltage drops in the amplifier's DC channel by improving the circuit structure, so as to solve the problem of high operating voltage of the operational amplifier in the prior art.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of a specific embodiment of the present application, a low-voltage integrated circuit operational amplifier is provided, comprising a multi-stage amplifier composed of transistors, characterized in that the DC channel of the amplifier only includes one transistor base-emitter voltage drop.

[0009] In some embodiments, the transistor is a bipolar transistor.

[0010] In some embodiments, the bipolar transistor is a germanium transistor.

[0011] In some embodiments, the DC path includes two resistor voltage drops, a transistor collector-emitter saturation voltage drop, and a transistor base-emitter voltage drop.

[0012] In some embodiments, the DC channel includes a level shifter.

[0013] In some embodiments, the level shifter includes an NPN / PNP transistor.

[0014] In some embodiments, the low voltage integrated circuit operational amplifier operates at a voltage of 1V.

[0015] In some embodiments, the low voltage integrated circuit operational amplifier operates at a voltage of ±0.5V.

[0016] According to the technical solution of the present application and the further improved technical solution in certain exemplary embodiments thereof, the present application has the following beneficial effects:

[0017] The integrated circuit operational amplifier of the present application reduces the number of transistor inter-electrode voltage drops in the amplifier's DC channel by improving the circuit structure. While meeting low-voltage operation requirements, it has low power consumption and high gain characteristics and can be applied to power management, portable devices, sensors, communication equipment and other systems.

[0018] The present application will be further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present application will be partially given in the following description, partially become apparent from the following description, or be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings that constitute part of this application are used to provide a further understanding of this application. The specific implementation methods, illustrative examples, and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0020] Figure 1 This is a schematic diagram of a typical integrated circuit operational amplifier preamplifier circuit structure;

[0021] Figure 2 for Figure 1 A schematic diagram of the circuit structure of a post-amplifier of the operational amplifier shown;

[0022] Figure 3This is a schematic diagram of the circuit structure of an integrated circuit operational amplifier pre-amplifier according to a specific embodiment of the present application;

[0023] Figure 4 for Figure 3 Schematic diagram of the post-amplifier circuit structure of the operational amplifier shown.

[0024] in, Figure 1 and Figure 2 It represents a complete schematic diagram of the integrated operational amplifier circuit structure. Figure 3 and Figure 4 This is a schematic diagram of the improved integrated circuit operational amplifier structure. For ease of layout, the integrated operational amplifier is divided into two figures. The terminals with the same name in the figure are connected to each other. The solid terminals are internal connection terminals, and the hollow terminals are integrated circuit leads. VDD is the power connection terminal; OUT is the output terminal; VBN is the bias voltage terminal of the NPN transistor, VBP is the bias voltage terminal of the PNP transistor; V IN- is the negative input terminal; V IN+ It is the positive input terminal. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the specific implementations, exemplary embodiments, and features thereof in this application may be combined with each other. This application will now be described in detail with reference to the accompanying drawings and in conjunction with the following content.

[0026] In order to enable those skilled in the art to better understand the solution of this application, the following will be combined with the drawings in the specific implementation methods and exemplary embodiments of this application to clearly and completely describe the technical solutions in the specific implementation methods and exemplary embodiments of this application. Obviously, the exemplary embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the specific implementation methods and exemplary embodiments in this application, all other implementation methods and embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of this application.

[0027] Example

[0028] like Figure 1 Figure 1 shows a typical low-voltage integrated circuit operational amplifier structure in the prior art. Transistors Q101-Q110 form the first-stage amplifier, while transistors Q201-Q211 form the second-stage amplifier. Together, they form the preamplifier stage of the integrated circuit operational amplifier. Transistors Q301-Q320 form the third-stage amplifier, also serving as the postamplifier (output stage) of the operational amplifier.

[0029] Figure 2Transistors Q301-Q311 form a rail-to-rail output control circuit, balancing the quiescent operating points of transistors Q319 and Q320. This integrated circuit operational amplifier does not use a cascode structure to increase gain, but instead employs a three-stage transistor amplifier structure to improve the open-loop gain of the low-voltage operational amplifier. The output stage employs a Darlington structure to enhance the current drive capability of the low-voltage operational amplifier.

[0030] In this integrated circuit operational amplifier, the DC channel voltage drop of the transistor amplifier determines the minimum operating voltage of the operational amplifier. Figure 1 and Figure 2 There are five DC channels in total, and they are numbered as channel ①, channel ②, channel ③, channel ④ and channel ⑤. Taking DC channel ① in the figure as an example, assuming that the voltage drops of resistors R21 and R16 are 50mV respectively, the VEC saturation voltage drop of transistor Q203 is 200mV, and the base-emitter voltages of the two transistors Q207 and Q110 are 0.7V respectively, then the total voltage drop of channel ① is 1.7V. It can also be seen that the total voltage drop of the remaining DC channel paths is 1.65V. The above five DC channels all contain two base-emitter voltage drops (depending on the polarity of the transistor, the current direction can be from emitter to base or base to emitter, which are called base-emitter voltage drops here). The voltage drop reaches 1.4V, which is the main part of the DC channel voltage drop and the main factor affecting the DC operating voltage of the transistor amplifier. Therefore, the minimum operating voltage of the operational amplifier is about 1.7V. In order to achieve normal operation at a lower operating voltage, Figure 1 、 Figure 2 The circuit structure needs to be further improved.

[0031] In the above-mentioned integrated circuit operational amplifier, the DC channel of the transistor amplifier contains two base-emitter voltage drops, which severely limits the minimum operating voltage of the operational amplifier. This application improves the circuit structure so that the DC channel voltage drop of the amplifier only contains one base-emitter voltage, allowing the multi-stage amplifier to operate at a 1V power supply voltage. The improved integrated circuit operational amplifier structure is shown in FIG. Figure 3 and Figure 4 shown.

[0032] analyze Figure 1 As can be seen from channel ①, the emitter voltage of transistors Q207-Q210 is directly fed back to the base of transistors Q109 and Q110. In order to ensure the normal operation of transistors Q109 and Q110, the emitter voltage of transistors Q207-Q210 must be greater than the base-emitter voltage of 0.7V plus the resistor voltage drop of 0.05V. To solve this problem, a level shifter is inserted between the emitters of transistors Q207-Q210 and the bases of transistors Q109 and Q110. The level shifter consists of Figure 3The PNP transistor Q211 and the resistor R25 form the circuit. In addition, the current source bias of the differential pair transistors Q207 to Q210 is changed to a resistor bias, reducing a saturation voltage drop in the path. Figure 3 In the figure, the total voltage drop of channel ① includes the voltage drop of resistor R21 (0.05V), the saturation voltage drop of transistor Q203 (0.2V), the base-emitter voltage of transistor Q207 (0.7V), and the voltage drop of resistor R25 (0.05V). The total voltage drop of this path is 1V.

[0033] In the improved circuit, the Darlington output structures in channels ② and ⑤ are changed to folded Darlington structures, reducing the saturation voltage drop in the path to 1 V. The folded Darlington structures form the third and fourth amplifier stages of the circuit.

[0034] delete Figure 2 The base voltages of the transistors Q307 and Q321, and the output tubes Q401 and Q402 are fed back to the rail-to-rail output control circuit through resistors R306 and R309 respectively. Figure 4 As shown, in static operation, if the base voltage of Q402 increases, the base voltage of Q311 increases, the base voltage of Q305 increases, the base voltage of Q312 decreases, the base voltages of Q313 and Q314 increase, and finally the base voltage of Q402 decreases. This loop forms negative feedback, which can keep Q402 working in a stable bias current condition. Figure 4 In the rail-to-rail output control circuit, the total voltage drop of channels ③ and ④ includes the voltage drop of two resistors totaling 0.1V, a saturation voltage drop of 0.2V, and a base-emitter voltage of 0.7V, for a total voltage drop of 1V.

[0035] In summary, each amplifier DC channel of the improved low-voltage operational amplifier only includes one transistor base-emitter voltage drop, and both can reach a 1V voltage drop, that is, the operational amplifier can operate under a 1V power supply voltage condition.

[0036] The utility model uses resistors as the tail current of the differential input pair of the operational amplifier and inserts a level shift circuit in the critical path, so that the minimum operating voltage of the operational amplifier is the sum of two resistor voltage drops, a transistor saturation voltage drop (collector-emitter saturation voltage drop) and a transistor base-emitter voltage drop. The operating voltage of 1V can be achieved, that is, when VDD is connected to a 1V voltage, the operational amplifier can work normally.

[0037] The above embodiment is a description of a single power supply structure. Those skilled in the art should know that the circuit described in the embodiment of the present application can also be directly applied to an operational amplifier with a dual power supply structure. The circuit can operate under a power supply voltage of ±0.5V, where the VDD terminal is connected to a +0.5V voltage and the GND terminal is connected to a -0.5V voltage. The specific circuit working principle will not be repeated here.

[0038] The circuit structure described in the embodiments of this application is well-suited for bipolar transistor operational amplifiers. Under conventional silicon integrated circuit process conditions, the operational amplifier can operate with a 1V DC power supply voltage. For amplifiers using germanium transistors, the transistor voltage drop can be further reduced, facilitating lower integrated circuit operating voltages and improving low-voltage operation stability.

Claims

1. A low voltage integrated circuit operational amplifier comprising a multi-stage amplifier composed of transistors, characterized in that: The DC channel of the amplifier comprises only a transistor base-emitter voltage drop, and the transistor base-emitter is connected in the DC channel.

2. The low voltage integrated circuit operational amplifier according to claim 1, wherein: The transistor is a bipolar transistor.

3. The low voltage integrated circuit operational amplifier according to claim 2, wherein: The bipolar transistor is a germanium transistor.

4. The low voltage integrated circuit operational amplifier according to claim 1, wherein: The DC channel includes two resistor voltage drops, a transistor collector-emitter saturation voltage drop, and a transistor base-emitter voltage drop.

5. The low voltage integrated circuit operational amplifier according to claim 1, wherein: The DC channel includes a level shifter.

6. The low voltage integrated circuit operational amplifier according to claim 5, wherein: The level shifter includes an NPN / PNP transistor.

7. The low voltage integrated circuit operational amplifier according to claim 1, wherein: The operating voltage of the low voltage integrated circuit operational amplifier is 1V.

8. The low voltage integrated circuit operational amplifier according to claim 1, wherein: The operating voltage of the low-voltage integrated circuit operational amplifier is ±0.5V.

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