A method for improving the core stability and gain of a millimeter-wave differential amplifier

Abstract

This invention discloses a method for improving the stability and gain of a millimeter-wave differential amplifier core. The stability and gain improvement comprises common-mode rejection enhancement and differential-mode gain enhancement. The millimeter-wave differential amplifier core includes a common-emitter amplifier circuit composed of a first transistor and a second transistor, and a common-base amplifier circuit composed of a third transistor and a fourth transistor. A first bias resistor and a second bias resistor are connected in series between the two bases of the first and second transistors. A third bias resistor and a fourth bias resistor are connected in series between the two bases of the third and fourth transistors. The emitter of the third transistor is connected to the collector of the first transistor, and the emitter of the fourth transistor is connected to the collector of the second transistor. A bridging capacitor is also connected between the two bases of the third and fourth transistors. This invention significantly improves the differential-mode gain characteristics of the millimeter-wave band amplifier core while simultaneously enhancing common-mode rejection by combining series capacitors with common-mode gain reduction.

Description

Technical Field

[0001] This invention belongs to the field of microwave integrated circuit technology, specifically relating to a technique for improving the core stability and gain of a millimeter-wave differential amplifier. Specifically, it employs a 130nm SiGe process and utilizes a combination of series capacitors and common-mode gain reduction to significantly improve the differential gain performance of the millimeter-wave amplifier core while simultaneously enhancing common-mode rejection. Background Technology

[0002] Transistor amplifiers are core components in the construction of radio frequency (RF) active circuits. Their gain and stability are crucial for the design of amplification units in RF transceiver links, such as low-noise amplifiers, power amplifiers, and driver amplifiers, directly determining whether the transceiver can function properly. The broadband characteristics of the millimeter-wave band enable ultra-high-speed wireless communication and high-precision radar technology; however, the increased frequency limits transistor performance. Therefore, gain enhancement techniques, namely positive feedback techniques, are necessary.

[0003] Traditional gain enhancement techniques primarily focus on increasing transconductance or amplifying voltage, such as neutralization capacitor technology, three-conductor feedback technology, common-base capacitor feedback technology in common-emitter common-base amplifiers, and G... max These technologies can significantly improve the maximum usable gain of transistors. However, the neutralizing capacitor technology introduces a cross-capacitor structure, which reduces the common-mode stability of the transistor and introduces the risk of common-mode oscillation. Although the other technologies mentioned above do not introduce an additional common-mode loop, they increase the common-mode gain while increasing the differential-mode gain. They lack common-mode rejection characteristics, so even with a highly symmetrical structure in millimeter-wave circuit design, high-gain amplifiers often introduce the risk of common-mode oscillation.

[0004] Therefore, although millimeter-wave frequency ranges offer a wide bandwidth for gain, the gain is significantly reduced due to the degradation of transistor core performance. Currently, positive feedback technology is widely used to improve gain; however, positive feedback technology requires high accuracy in transistor modeling and carries a high risk of common-mode oscillation. Therefore, there is a need to invent a millimeter-wave differential amplifier core that can improve common-mode stability without sacrificing differential-mode gain characteristics. Summary of the Invention

[0005] Technical Problem: To solve the above problems, this invention provides a method for improving the stability and gain of a millimeter-wave differential amplifier core. Specifically, a bridging capacitor is introduced between the bases of the common-base transistors in a differential common-emitter common-base amplifier, or a feedback resistor and a feedback capacitor are connected in series between the base of the common-emitter amplifier and the collector of the common-base amplifier. This achieves improvement in differential-mode gain and common-mode rejection of the amplifier core, significantly improving the gain and stability of the amplifier core.

[0006] Technical Solution: To solve the above-mentioned technical problems, this invention proposes a method for improving the core stability and gain of a millimeter-wave differential amplifier. The technical solution adopted is as follows:

[0007] The stability and gain enhancement consist of common-mode rejection enhancement and differential-mode gain enhancement; the millimeter-wave differential amplifier core includes a common-emitter amplifier circuit composed of a first transistor and a second transistor, and a common-base amplifier circuit composed of a third transistor and a fourth transistor; a first bias resistor and a second bias resistor are connected in series between the two bases of the first transistor and the second transistor; a third bias resistor and a fourth bias resistor are connected in series between the two bases of the third transistor and the fourth transistor; the emitter of the third transistor is connected to the collector of the first transistor, and the emitter of the fourth transistor is connected to the collector of the second transistor; a bridging capacitor is also connected between the two bases of the third transistor and the fourth transistor.

[0008] A feedback resistor and a feedback capacitor are connected in series between the collector of the third transistor and the base of the first transistor, and a feedback resistor and a feedback capacitor are connected in series between the collector of the fourth transistor and the base of the second transistor.

[0009] The differential-mode gain enhancement is achieved by inputting signals of equal amplitude and 180-degree phase difference, and the gain is increased by transistors; the common-mode rejection enhancement is achieved by inputting signals of equal amplitude and same phase, and the difference between the common-mode gain and differential-mode gain of the amplifier core is increased.

[0010] The bridging capacitor and the feedback capacitor are composed of a metal-dielectric-metal structure, which consists of a top layer of thick metal, a second-to-top layer of thick metal, and a dielectric between the two metal layers. The metal layers are connected by metal vias that penetrate the dielectric layer.

[0011] The first, second, third, and fourth transistors form a differential common-emitter common-base structure through stacking technology. The first, second, third, and fourth bias resistors are respectively connected to the base of the transistors to achieve radio frequency suppression and DC power supply.

[0012] The bridging capacitor, feedback resistor, and feedback capacitor may be used individually or in combination depending on process characteristics, transistor size, frequency band selection, gain requirements, etc.

[0013] The first transistor, second transistor, third transistor, fourth transistor, first bias resistor, second bias resistor, third bias resistor, fourth bias resistor, bridging capacitor, feedback resistor, and feedback capacitor are all manufactured using silicon-based semiconductor integrated circuit technology.

[0014] The first differential input signal is connected to the base of the first transistor, and the second differential input signal is connected to the base of the second transistor; the first differential output signal is connected to the collector of the third transistor, and the second differential output signal is connected to the collector of the fourth transistor.

[0015] Beneficial effects:

[0016] 1) By connecting the base of the common-base transistor in the differential common-emitter common-base amplifier core with a series capacitor, the differential-mode gain and common-mode rejection characteristics of the amplifier core are effectively improved, and the stability of the amplifier core is greatly enhanced.

[0017] 2) The structure is simple, the capacitor size is reduced, and the requirements for capacitor quality factor are lowered.

[0018] 3) Feedback resistors and feedback capacitors can be used to further improve common-mode rejection characteristics according to design requirements.

[0019] 4) It is suitable for amplifier core design in microwave communication systems that require high stability, and has the characteristics of high gain and good stability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the core stability and gain enhancement of the millimeter-wave differential amplifier of the present invention.

[0021] Figure 2 These are the common-mode equivalent circuit and differential-mode equivalent circuit of the present invention; Figure 2 (a) in the diagram is the common-mode equivalent circuit. Figure 2 (b) in the diagram is the differential-mode equivalent circuit;

[0022] Figure 3 This invention adapts to changes in the bridging capacitance. Figure 3 In the diagram, (a) represents the maximum gain change in the differential mode. Figure 3 (b) in the diagram represents the change in common-mode suppression characteristics;

[0023] Figure 4 This is the resonant characteristic curve of the capacitor layout and size variation used in this invention;

[0024] Figure 5 This is a schematic diagram of the enhanced amplification core of the present invention, which uses feedback resistors and feedback capacitors to further improve the differential-mode gain and common-mode rejection characteristics of the amplifier core;

[0025] Figure 6 This relates to the differential-mode maximum gain and common-mode rejection characteristics of the enhanced core of this invention.

[0026] The diagram shows: first transistor Q1, second transistor Q2, third transistor Q3, fourth transistor Q4, first bias resistor R1, second bias resistor R2, third bias resistor R3, fourth bias resistor R4, bridging capacitor CS, feedback resistor Rf, and feedback capacitor Cf. Detailed Implementation

[0027] This invention designs a method for improving the core stability and gain of a millimeter-wave differential amplifier. The core circuit of the millimeter-wave differential amplifier consists of a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth transistor Q4, a first bias resistor R1, a second bias resistor R2, a third bias resistor R3, a fourth bias resistor R4, a bridging capacitor CS, a feedback resistor Rf, and a feedback capacitor Cf.

[0028] Specifically, the first and third transistors form a common-emitter, common-base amplification core structure, as do the second and fourth transistors. A bridging capacitor CS is placed in series with the bases of the third and fourth transistors. In differential-mode equivalent circuits, the bridging capacitor CS achieves double-capacitor positive feedback, significantly improving common-mode amplification gain, reducing the Q-value requirement for capacitors, and decreasing the overall core size. In common-mode equivalent circuits, the bridging capacitor does not improve common-mode gain, thus reducing the risk of common-mode oscillation. Furthermore, in RF links with high common-mode rejection requirements, the bridging capacitor CS can be further increased by connecting feedback resistors and capacitors between the first and third transistors, and between the second and fourth transistors; this is called an enhanced core.

[0029] The circuit adopts a symmetrical mirror layout, which effectively reduces the risk of common-mode oscillation in the RF link.

[0030] This invention improves the differential-mode gain and common-mode rejection characteristics of an amplifier core through a circuit topology using a bridging capacitor and RC feedback, thereby enhancing the stability of the amplifier core. This circuit is suitable for drive amplifiers, low-noise amplifiers, power amplifiers, and other devices in the transceiver link of high-performance millimeter-wave communication radar systems, offering advantages such as high gain and high stability.

[0031] The invention will now be further described with reference to the accompanying drawings.

[0032] like Figure 1 and Figure 5 As shown:

[0033] The stability and gain enhancement consist of common-mode rejection enhancement and differential-mode gain enhancement; the millimeter-wave differential amplifier core includes a common-emitter amplifier circuit composed of a first transistor Q1 and a second transistor Q2, and a common-base amplifier circuit composed of a third transistor Q3 and a fourth transistor Q4; a first bias resistor R1 and a second bias resistor R2 are connected in series between the two bases of the first transistor Q1 and the second transistor Q2; a third bias resistor R3 and a fourth bias resistor R4 are connected in series between the two bases of the third transistor Q3 and the fourth transistor (Q4); the emitter of the third transistor Q3 is connected to the collector of the first transistor Q1, and the emitter of the fourth transistor Q4 is connected to the collector of the second transistor Q2; a bridging capacitor CS is also connected between the two bases of the third transistor Q3 and the fourth transistor Q4.

[0034] A feedback resistor Rf and a feedback capacitor Cf are connected in series between the collector of the third transistor Q3 and the base of the first transistor Q1. A feedback resistor Rf and a feedback capacitor Cf are also connected in series between the collector of the fourth transistor Q4 and the base of the second transistor Q2.

[0035] The differential-mode gain enhancement is achieved by inputting signals of equal amplitude and 180-degree phase difference, and the gain is increased by transistors; the common-mode rejection enhancement is achieved by inputting signals of equal amplitude and same phase, and the difference between the common-mode gain and differential-mode gain of the amplifier core is increased.

[0036] The bridging capacitor CS and the feedback capacitor Cf are composed of a metal-dielectric-metal structure, which consists of a top layer of thick metal, a second-to-top layer of thick metal, and a dielectric between the two metal layers. The metal layers are connected by metal vias that penetrate the dielectric layer.

[0037] The first transistor Q1, the second transistor Q2, the third transistor Q3, and the fourth transistor Q4 form a differential common-emitter common-base structure through stacking technology. The first bias resistor R1, the second bias resistor R2, the third bias resistor R3, and the fourth bias resistor R4 are respectively connected to the base of the transistor to realize radio frequency suppression and DC power supply.

[0038] The bridging capacitor CS, feedback resistor Rf, and feedback capacitor Cf are used individually or in combination depending on process characteristics, transistor size, frequency band selection, gain requirements, etc.

[0039] The first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, the first bias resistor R1, the second bias resistor R2, the third bias resistor R3, the fourth bias resistor R4, the bridging capacitor CS, the feedback resistor Rf, and the feedback capacitor Cf are all fabricated using silicon-based semiconductor integrated circuit technology.

[0040] The first differential input signal Vin is connected to the base of the first transistor Q1, and the second differential input signal Vip is connected to the base of the second transistor Q2; the first differential output signal Von is connected to the collector of the third transistor Q3, and the second differential output signal Vop is connected to the collector of the fourth transistor Q4.

[0041] Figure 2 This is the common-mode and differential-mode equivalent circuit of the present invention. As shown in the common-mode and differential-mode equivalent circuit, in the differential-mode equivalent, the bridging capacitor Cs achieves the characteristic of double capacitance positive feedback, which greatly improves the common-mode amplification gain, reduces the requirement for capacitor Q value, and reduces the overall core size; in the common-mode equivalent, the bridging capacitor does not improve the common-mode gain, thus reducing the risk of common-mode oscillation.

[0042] Figure 3 This presents the simulation results of the differential-mode maximum gain and common-mode rejection ratio as the bridging capacitance changes. This invention achieves a reduction of half the capacitance value in the differential-mode case compared to the traditional parallel capacitor method, while maintaining a common-mode rejection ratio greater than 10dB.

[0043] Figure 4 This is the resonant characteristic curve of the capacitor layout and size variations used in this invention. As the capacitor size increases, the resonant frequency decreases under this process, and the capacitance value fluctuates significantly. By employing this invention, the required capacitance value is significantly reduced, thereby achieving a wider differential-mode gain over a broader frequency range.

[0044] Figure 6 This invention relates to the enhanced core's differential-mode maximum gain and common-mode rejection characteristics. By further improving Cs and adding Rf and Cf feedback, the common-mode rejection is further enhanced.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the core stability and gain of a millimeter-wave differential amplifier, characterized in that, The stability and gain enhancement consist of common-mode rejection enhancement and differential-mode gain enhancement. The millimeter-wave differential amplifier core includes a common-emitter amplifier circuit composed of a first transistor (Q1) and a second transistor (Q2), and a common-base amplifier circuit composed of a third transistor (Q3) and a fourth transistor (Q4). A first bias resistor (R1) and a second bias resistor (R2) are connected in series between the two bases of the first transistor (Q1) and the second transistor (Q2). A third bias resistor (R3) and a fourth bias resistor (R4) are connected in series between the two bases of the third transistor (Q3) and the fourth transistor (Q4). The emitter of the third transistor (Q3) is connected to the collector of the first transistor (Q1), and the emitter of the fourth transistor (Q4) is connected to the collector of the second transistor (Q2). A bridging capacitor (CS) is also connected between the two bases of the third transistor (Q3) and the fourth transistor (Q4).

2. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 1, characterized in that, A feedback resistor (Rf) and a feedback capacitor (Cf) are connected in series between the collector of the third transistor (Q3) and the base of the first transistor (Q1). A feedback resistor (Rf) and a feedback capacitor (Cf) are also connected in series between the collector of the fourth transistor (Q4) and the base of the second transistor (Q2).

3. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 2, characterized in that, The differential-mode gain enhancement is achieved by inputting signals of equal amplitude and 180-degree phase difference, and the gain is increased by transistors; the common-mode rejection enhancement is achieved by inputting signals of equal amplitude and same phase, and the difference between the common-mode gain and differential-mode gain of the amplifier core is increased.

4. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 3, characterized in that, The bridging capacitor (CS) and feedback capacitor (Cf) are composed of a metal-dielectric-metal structure, including a top layer of thick metal, a second-to-top layer of thick metal, and a dielectric between the two metal layers. The metal layers are connected by metal vias that penetrate the dielectric layer.

5. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 4, characterized in that, The first transistor (Q1), the second transistor (Q2), the third transistor (Q3), and the fourth transistor (Q4) form a differential common-emitter common-base structure through stacking technology. The first bias resistor (R1), the second bias resistor (R2), the third bias resistor (R3), and the fourth bias resistor (R4) are respectively connected to the base of the transistor to realize radio frequency suppression and DC power supply.

6. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 5, characterized in that, The bridging capacitor (CS), feedback resistor (Rf), and feedback capacitor (Cf) may be used individually or in combination depending on process characteristics, transistor size, frequency band selection, gain requirements, etc.

7. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 6, characterized in that, The first transistor (Q1), the second transistor (Q2), the third transistor (Q3), the fourth transistor (Q4), the first bias resistor (R1), the second bias resistor (R2), the third bias resistor (R3), the fourth bias resistor (R4), the bridging capacitor (CS), the feedback resistor (Rf), and the feedback capacitor (Cf) are all fabricated using silicon-based semiconductor integrated circuit technology.

8. The method for improving the core stability and gain of a millimeter-wave differential amplifier according to claim 7, characterized in that, The first differential input signal (Vin) is connected to the base of the first transistor (Q1), and the second differential input signal (Vip) is connected to the base of the second transistor (Q2); the first differential output signal (Von) is connected to the collector of the third transistor (Q3), and the second differential output signal (Vop) is connected to the collector of the fourth transistor (Q4).

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