CN113206647A

CN113206647A - Circuit feedback structure

Info

Publication number: CN113206647A
Application number: CN202110475945.9A
Authority: CN
Inventors: 吴奕蓬
Original assignee: Xi'an Borui Jixin Electronic Technology Co ltd
Current assignee: Xi'an Borui Jixin Electronic Technology Co ltd
Priority date: 2021-04-29
Filing date: 2021-04-29
Publication date: 2021-08-03

Abstract

The invention is suitable for the field of microelectronics, and discloses a circuit feedback structure arranged between a radio-frequency signal input end and a radio-frequency signal output end, which comprises a radio-frequency main circuit, a bias circuit, a feedback resistor and a capacitor connected with the feedback resistor in parallel; the radio frequency signal input from the radio frequency signal input end is divided into two paths, one path of signal reaches the radio frequency signal output end through the feedback resistor, and the other path of signal reaches the radio frequency signal output end through the capacitor and the radio frequency main circuit; one end of the bias circuit is connected with a power supply end, and the other end of the bias circuit is connected with the input end of the radio frequency main circuit; the circuit feedback structure can solve the problem of low-frequency stability in a chip under the condition of keeping the advantages of the traditional resistor-capacitor circuit feedback structure, and the design reliability of the radio frequency amplifier is improved.

Description

Circuit feedback structure

Technical Field

The invention relates to the technical field of microelectronics, in particular to a circuit feedback structure.

Background

Radio frequency amplifiers are widely used in radio frequency systems. The feedback circuit is the most common measure for improving the performance of the radio frequency amplifier, and can improve the gain flatness of the amplifier, improve the return loss of a port, enhance the stability of the circuit and improve the linearity of the circuit.

Feedback circuit configurations are classified into series negative feedback and parallel negative feedback, and both negative feedback configurations are generally applied to improve performance in one amplifier. The series negative feedback circuit usually adopts a resistor or an inductor connected in series with the source or the emitter of a transistor, and has obvious influence on the performances of the gain, the noise coefficient, the output power and the like of an amplifier, and the selection of a series negative feedback element is very limited under the specified performance condition.

As shown in fig. 2, the parallel negative feedback circuit usually crosses the resistor-capacitor series structure in parallel between the rf input and rf signal output terminals, the resistor mainly plays a feedback role, and the capacitor plays a role of isolating dc. However, as the frequency decreases, the impedance of the capacitor gradually increases, the feedback effect gradually decreases, and conditions are stable and even oscillation easily occurs in a lower frequency band outside the working frequency band. One way to improve the stability at low frequencies is to increase the capacitance of the feedback branch, but this requires a large capacitance to cover the very low frequencies, which is often unacceptable in chip designs.

Disclosure of Invention

The invention aims to provide a circuit feedback structure which can solve the problem of low-frequency stability in a chip under the condition of keeping the advantages of the traditional resistor-capacitor circuit feedback structure.

In order to achieve the purpose, the invention provides the following scheme:

a circuit feedback structure is arranged between a radio frequency signal input end and a radio frequency signal output end and comprises a radio frequency main circuit, a bias circuit, a feedback resistor and a capacitor connected with the feedback resistor in parallel; the radio frequency signal input from the radio frequency signal input end is divided into two paths, one path of signal reaches the radio frequency signal output end through the feedback resistor, and the other path of signal reaches the radio frequency signal output end through the capacitor and the radio frequency main circuit; one end of the bias circuit is connected with a power supply end, and the other end of the bias circuit is connected with the input end of the radio frequency main circuit.

Preferably, the radio frequency main circuit includes an MOS transistor, a gate of the MOS transistor is connected to the capacitor and the bias circuit, a drain of the MOS transistor is connected to the radio frequency signal output terminal, and a source of the MOS transistor is grounded.

The circuit feedback structure connection mode provided by the invention enables the input end to be connected to the input end of the radio frequency main circuit through the capacitor on the parallel feedback branch circuit and to be connected to the output end of the radio frequency main circuit through the resistor on the parallel feedback branch circuit. In the working frequency band, a radio frequency signal is transmitted to the input end of a radio frequency main circuit through a capacitor, and the parallel feedback performance is the same as that of the traditional structure; under the condition of low frequency, the capacitor on the feedback branch is high in impedance and is approximately a radio frequency open circuit, and meanwhile, the capacitor enters the radio frequency signal output end through the feedback resistor, so that the problem of low frequency stability can be solved in a chip under the condition that the advantages of the feedback structure of the traditional resistor-capacitor circuit are kept, and the design reliability of the radio frequency amplifier is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a circuit feedback structure provided by an embodiment of the present invention;

FIG. 2 is a conventional resistor-capacitor parallel degeneration architecture;

fig. 3 is a comparison graph of low frequency stability of a circuit feedback structure provided by an embodiment of the present invention and a conventional resistor-capacitor parallel negative feedback structure.

The reference numbers illustrate:

10. a radio frequency main circuit; 20. a bias circuit; 30. a feedback resistor R; 40. a capacitance C.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

It will also be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

As shown in fig. 1, the circuit feedback structure according to an embodiment of the present invention is a circuit feedback structure, and compared with the conventional passive RC feedback, only the connection mode is changed without changing other parts of the circuit, so that the low-frequency stability can be effectively improved, and the circuit feedback structure has a relatively high versatility and can be applied to almost all parallel feedback structures.

Referring to fig. 1 and fig. 3, the circuit feedback structure according to the embodiment of the present invention is disposed between the rf signal Input terminal and the rf signal Output terminal, and includes a rf main circuit 10, a bias circuit 20, a feedback resistor R30, and a capacitor C40 connected in parallel to the feedback resistor R30; a radio-frequency signal Input from a radio-frequency signal Input end is divided into two paths, one path of signal reaches a radio-frequency signal Output end Output through a feedback resistor R30, and the other path of signal reaches the radio-frequency signal Output end through a capacitor C40 and a radio-frequency main circuit 10; one end of the bias circuit 20 is connected to the power supply terminal VCC, and the other end is connected to the input terminal of the main rf circuit 10, so as to provide bias current for the main rf circuit 10, and the dc isolation is realized between the output terminal and the power supply terminal VCC through the capacitor C40 on the feedback branch, without affecting the operation of the bias circuit 20. The rf signal Input is not directly connected to the Input of the rf main circuit 10 as is conventional, but is connected to the Input of the rf main circuit 10 through a capacitor C40 in the parallel feedback branch. In the working frequency band, the radio frequency signal is transmitted to the input end of the radio frequency main circuit 10 through the capacitor C40, and the parallel feedback performance is the same as that of the traditional structure; under the low-frequency condition, the impedance of the capacitor C40 on the feedback branch is large, so that the circuit is nearly open at radio frequency, and simultaneously the circuit enters the radio frequency signal Output end through the feedback resistor R30.

Specifically, the radio frequency main circuit 10 includes an MOS transistor, a gate of the MOS transistor is connected to the capacitor C40 and the bias circuit 20, a drain of the MOS transistor is connected to the radio frequency signal Output terminal Output, and a source of the MOS transistor is grounded.

The circuit feedback structure of the embodiment of the invention solves the problem of low-frequency stability in a chip by changing the traditional resistor-capacitor parallel negative feedback connection mode under the condition of keeping the advantages of the traditional resistor-capacitor circuit feedback structure, and improves the design reliability of the radio frequency amplifier.

Referring to fig. 3, fig. 3 shows a low frequency stability comparison curve of the feedback structure of the circuit provided by the embodiment of the present invention and the conventional resistor-capacitor parallel negative feedback structure. The red curve represents the stability curve of the feedback structure of the circuit of the invention, and the black curve represents the stability curve of the traditional resistor-capacitor parallel negative feedback structure. As can be seen from fig. 3, the circuit feedback structure provided by the embodiment of the invention can effectively improve the low frequency stability.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A circuit feedback structure is arranged between a radio frequency signal input end and a radio frequency signal output end, and is characterized in that the circuit feedback structure comprises a radio frequency main circuit, a bias circuit, a feedback resistor and a capacitor connected with the feedback resistor in parallel; the radio frequency signal input from the radio frequency signal input end is divided into two paths, one path of signal reaches the radio frequency signal output end through the feedback resistor, and the other path of signal reaches the radio frequency signal output end through the capacitor and the radio frequency main circuit; one end of the bias circuit is connected with a power supply end, and the other end of the bias circuit is connected with the input end of the radio frequency main circuit.

2. The circuit feedback structure as claimed in claim 1, wherein the rf main circuit includes a MOS transistor, a gate of the MOS transistor is connected to the capacitor and the bias circuit, a drain of the MOS transistor is connected to the rf signal output terminal, and a source of the MOS transistor is grounded.