Broadband single-ended input differential amplifier

Abstract

The invention discloses a broadband single-ended input differential amplifier, which comprises an unbalanced single-ended to differential input amplification stage, a self-bias feedback balance differential output amplification stage, a broadband feedback differential load network and a broadband feedback path, the unbalanced single-ended to differential input amplification stage is an input stage circuit of the broadband single-ended input differential amplifier, internally comprises a cascaded inverting amplifier, and converts an input signal into a differential intermediate stage signal; the self-biased feedback balance differential output amplification stage is an output stage circuit of the broadband single-ended input differential amplifier, and the differential intermediate stage signal forms a final differential output signal; and the broadband feedback differential load network is connected in parallel to the differential output end of the self-biased feedback balance differential output stage, and feeds back a differential output signal to the unbalanced single-ended to differential input amplification stage through the broadband feedback path to realize bandwidth matching.

Description

Technical Field

[0001] The present invention relates to the design of radio frequency front-end integrated circuits, and particularly to a broadband single-ended input differential amplifier. Background Art

[0002] As a key module in the radio frequency signal link, a radio frequency amplifier is required to achieve good and large gain at low current consumption for signal amplification, and at the same time has excellent characteristics such as noise figure and power linearity.

[0003] Traditional broadband single-ended to differential amplifiers, such as Figure 1 shown, the main circuit includes four transistors M1, M2, M3, and M4. Among them, the common-gate transistor M1 and the common-source transistor M2 form the input stage of the amplifier, converting the single-ended input signal RFin into a differential signal, and then respectively forming differential output signals RF0+ and RF0- through the output stage composed of the common-gate transistors M3 and M4.

[0004] The disadvantages of the above circuit are as follows: The common-gate transistor M1 and the common-source transistor M2 are used to achieve broadband input matching and single-ended to differential function. However, limited by the limited signal gain performance of the common-gate transistor M1, the overall signal gain of the amplifier is restricted; at the same time, when converted into a differential signal and directly differentially output through the common-gate output stages M3 and M4, the output stage gain is also insufficient. Therefore, the overall gain of the amplifier system is insufficient and needs to be improved and enhanced.

[0005] In addition, two differential branches respectively formed by the common-gate transistor M1 and the common-gate transistor M3 and the common-source transistor M2 and the common-gate transistor M4 are common-gate - common-gate cascade and common-source - common-gate cascade respectively. While the system gain is limited, it is difficult for the gain amplitude and phase delay of the differential signal to be equal in magnitude and opposite in phase over a wide bandwidth, and it is very difficult to achieve good differential signal amplification output, which needs to be improved and adjusted. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a broadband single-ended input differential amplifier to improve the overall gain of the amplifier, broadband matching, and the balance of differential signals.

[0007] To solve the above problems, the present invention provides a broadband single-ended input differential amplifier, comprising: the broadband single-ended input differential amplifier includes an unbalanced single-ended to differential input amplification stage, a self-biased feedback balanced differential output amplification stage, a broadband feedback differential load network, and a broadband feedback path; The unbalanced single-ended to differential input amplification stage is the input stage circuit of the broadband single-ended input differential amplifier, and its internal includes two cascaded inverting amplifiers, converting the single-ended input signal into a differential intermediate-stage signal; The self - biased feedback balanced differential output stage is the output stage circuit of the broadband single - ended input differential amplifier, cascaded at the rear end of the unbalanced single - ended to differential input amplifier stage, further processing the differential intermediate - stage signal and forming the final differential output signal; The broadband feedback differential load network is connected in parallel to the differential output terminals of the self - biased feedback balanced differential output stage, feeding back the differential output signal to the unbalanced single - ended to differential input amplifier stage through the broadband feedback path to achieve broadband matching.

[0008] Further, the unbalanced single - ended to differential input amplifier stage includes a cascaded first inverter and a second inverter. The input terminal of the second inverter is connected to the output terminal of the first inverter, and the input terminal of the first inverter is connected to the input signal; the output terminal of the first inverter outputs the first path of the differential intermediate - stage signal, that is, the signal inverted with respect to the input signal, which is connected to the first differential input terminal of the self - biased feedback balanced differential output stage; the output terminal of the second inverter outputs the second path of the differential intermediate - stage signal, that is, the signal in phase with the input signal, which is connected to the second differential input terminal of the self - biased feedback balanced differential output stage.

[0009] Further, the self - biased feedback balanced differential output stage receives the differential intermediate - stage signal, performs cross - input coupling processing on the unbalanced differential intermediate - stage signal to achieve differential signal balance processing, and at the same time adjusts the phase and gain amplitude through self - biased feedback to optimize the differential signal balance and large - reverse, and improves signal gain and broadband matching; the self - biased feedback balanced differential output stage shares the DC bias with the unbalanced single - ended to differential input amplifier stage.

[0010] Further, for the unbalanced single - ended to differential input amplifier stage, its circuit includes: An input inductor, first and second transistors, first and second input capacitors, first and second inductors, and first and second resistors; The input signal is connected to the gate terminal of the first transistor through the input inductor and the first input capacitor. The drain terminal of the first transistor outputs one path of the differential intermediate - stage signal. The gate terminal of the first transistor is connected to the first gate voltage through the first resistor, and the source terminal of the first transistor is grounded through the second inductor.

[0011] The drain terminal of the first transistor is also connected to the gate terminal of the second transistor through the second input capacitor. The gate terminal of the second transistor is connected to the second gate voltage through the second resistor; the drain terminal of the second transistor outputs the other path of the differential intermediate - stage signal, and the source terminal of the second transistor is grounded.

[0012] Further, the self - biased feedback balanced differential output amplifier stage includes a third transistor, a fourth transistor, a first self - biasing resistor, a second self - biasing resistor, a first feedback capacitor, and a second feedback capacitor; The gate of the third transistor is connected to the source of the fourth transistor through the second feedback capacitor, and the gate of the fourth transistor is connected to the source of the third transistor through the first feedback capacitor. The source of the third transistor is the input terminal of the self - biased feedback balanced differential output amplifier stage and is connected to one path of the output differential intermediate - stage signal; the source of the fourth transistor is the other input terminal of the self - biased feedback balanced differential output amplifier stage and is connected to the other path of the output differential intermediate - stage signal; A first self - biasing resistor is connected in series between the drain and the gate of the third transistor, and a second self - biasing resistor is connected in series between the drain and the gate of the fourth transistor; The drains of the third transistor and the fourth transistor are the differential output terminals of the self - biased feedback balanced differential output amplifier stage.

[0013] Further, the broadband feedback differential load network includes an inductive load, a first parallel resistor, a second parallel resistor, a first output capacitor, and a second output capacitor; the inductive load is connected between the two differential output terminals of the self - biased feedback balanced differential output amplifier stage, and its center tap is connected to the power supply. The first and second parallel resistors are in parallel with the inductive load and are respectively connected between the two differential output terminals of the self - biased feedback balanced differential output amplifier stage and the center tap of the inductive load. The differential output terminals of the differential intermediate - stage respectively output the final differential output signals of the broadband single - ended input differential amplifier through the first output capacitor and the second output capacitor; The inductive load and the parallel resistor Rdi are used to adjust the bandwidth of the matching network.

[0014] The second inductor of the unbalanced single - ended to differential input amplifier stage and the inductive load of the broadband feedback differential load network form a transformer coupling to form a broadband feedback path.

[0015] For the broadband single - ended input differential amplifier of the present invention, the unbalanced single - ended to differential input amplifier stage is composed of two cascaded common - source inverting amplifier stages, both of which can provide good signal gain and improve the overall gain of the amplifier; the input amplifier stage and the output amplifier stage share the DC bias current, improving the signal gain without increasing additional DC power consumption and achieving low - power improvement of energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic circuit structure diagram of a traditional broadband single - ended to differential amplifier.

[0017] Figure 2 is a schematic circuit topology diagram of the broadband single - ended input differential amplifier shown in the present invention.

[0018] Figure 3 It is a specific implementation example of the broadband single-ended input differential amplifier circuit shown in the present invention.

[0019] Figure 4 It is a comparison of the gain curves between the circuit of the present invention and the traditional circuit. Specific Embodiments

[0020] The following provides specific embodiments of the present invention in conjunction with the accompanying drawings to clearly and completely describe the technical solutions in the present invention. However, the present invention is not limited to the following embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. According to the following description and the claims, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, only for the purpose of conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0021] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented here. On the contrary, providing these embodiments will make the disclosure thorough and complete and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated, and the same reference numerals throughout the drawings represent the same elements. It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as the second element, component, region, layer or part.

[0022] The present invention proposes a novel broadband single-ended input differential amplifier circuit structure and design implementation, and designs an unbalanced single-ended to differential input amplification stage, a self-biased feedback balanced differential output stage, and a broadband feedback differential load network. Without increasing the DC power consumption, it can improve the overall gain and broadband matching of the amplifier and the balance of differential signals.

[0023] AsFigure 2 As shown, it is a schematic diagram of the circuit topology of the broadband single-ended input differential amplifier provided by the present invention, which mainly consists of three major modules, including an unbalanced single-ended to differential input amplification stage, a self-biased feedback balanced differential output amplification stage, and a broadband feedback differential load network.

[0024] The unbalanced single-ended to differential input amplification stage is the input stage circuit of the broadband single-ended input differential amplifier. It internally contains two cascaded inverting amplifiers, which convert the single-ended input signal into a differential intermediate-stage signal. The first-stage inverting amplifier outputs one path of the differential intermediate-stage signal, and the second-stage inverting amplifier outputs another path of the differential intermediate-stage signal. The unbalanced single-ended to differential input amplification stage is composed of two cascaded common-source inverting amplifiers, both of which can provide good signal gain and improve the overall gain of the amplifier.

[0025] The differential intermediate-stage signal is provided to the self-biased feedback balanced differential output amplification stage.

[0026] The self-biased feedback balanced differential output amplification stage is the output stage circuit of the broadband single-ended input differential amplifier, cascaded at the back end of the unbalanced single-ended to differential input amplification stage, and further processes the differential intermediate-stage signal to form the final differential output signal.

[0027] The self-biased feedback balanced differential output amplification stage performs cross-input coupling processing on the unbalanced differential signal output by the input stage to achieve differential signal balance processing. At the same time, it adjusts the phase and gain amplitude through self-biased feedback to optimize the differential signal balance and large reverse, and can improve the signal gain and system gain.

[0028] At the same time, the unbalanced single-ended to differential input amplification stage and the self-biased feedback balanced differential output amplification stage are directly stacked to share the DC bias current, improving the signal gain without increasing additional DC power consumption, and achieving low power consumption and improved energy efficiency.

[0029] The broadband feedback differential load network is connected in parallel at the differential output terminals of the self-biased feedback balanced differential output stage. There is a broadband feedback path between the input amplification stage and the broadband feedback differential load network, and the differential output signal is fed back to the signal input terminal of the unbalanced single-ended to differential input amplification stage through the broadband feedback path to achieve self-biased feedback of the output signal. The negative feedback network can improve the input matching bandwidth, and combined with the self-biased feedback of the output stage, achieve broadband input and output matching.

[0030] The above is the circuit topology proposed by the present invention. In one embodiment, it can be adopted as Figure 3It is implemented by the specific circuit shown. This embodiment only provides one circuit implementation method, and those skilled in the art can adopt any circuit structure that can implement the functions of the present invention based on the circuit topology of the present invention.

[0031] Figure 3 The unbalanced single-ended to differential input amplification stage circuit module shown in the figure is composed of two cascaded common-source amplifiers. The input stage is a common-source amplifier with negative feedback of the gate inductor (input inductor) Lg, and the source feedback inductor Ls is broadband coupled in the same direction as the output inductive load Lo to provide a feedback path. The first transistor M1, the second transistor M2, the first input capacitor Cin1, the second input capacitor Cin2, the first resistor Rg1, and the second resistor Rg2.

[0032] The single-ended input signal RFin is connected to the gate terminal of the first transistor M1 through the input inductor Lg and the first input capacitor Cin1. The drain terminal of the first transistor M1 outputs one of the differential intermediate-stage signals, that is, the signal inverted with respect to the input signal RFin; the gate terminal of the first transistor is connected to the first gate voltage Vg1 through the first resistor.

[0033] The drain terminal of the first transistor M1 is also connected to the gate terminal of the second transistor M2 through the second input capacitor Cin2. The gate terminal of the second transistor is connected to the second gate voltage Vg2 through the second resistor; the drain terminal of the second transistor M2 outputs the other path of the differential intermediate-stage signal, that is, the signal in phase with the input signal RFin; the source terminal of the second transistor is grounded.

[0034] The above unbalanced single-ended to differential input amplification stage circuit provides a differential intermediate-stage signal output to the self-biased feedback balanced differential output amplification stage.

[0035] The self-biased feedback balanced differential output amplification stage is a cross-coupled amplifier, including the third transistor M3, the fourth transistor M4, the first self-biased resistor Rf1, the second self-biased resistor Rf2, the first feedback capacitor Cx1, and the second feedback capacitor Cx2.

[0036] The gate of the third transistor M3 is connected to the source terminal of the fourth transistor M4 through the second feedback capacitor Cx2. The gate of the fourth transistor M4 is connected to the source terminal of the third transistor M3 through the first feedback capacitor Cx1. The drain terminal of the third transistor M3 is the input terminal of the self-biased feedback balanced differential output amplification stage and is connected to one of the output differential intermediate-stage signals; the drain terminal of the fourth transistor is the other input terminal of the self-biased feedback balanced differential output amplification stage and is connected to the other path of the output differential intermediate-stage signal.

[0037] A first self - biasing resistor Rf1 is connected in series between the drain terminal and the gate terminal of the third transistor M3, and a second self - biasing resistor Rf2 is connected in series between the drain terminal and the gate terminal of the fourth transistor M4.

[0038] The drain terminals of the third transistor M3 and the fourth transistor M4 are the differential output terminals of the self - biasing feedback balanced differential output amplifier stage.

[0039] The self - biasing feedback balanced differential output amplifier stage realizes the balance of differential signals. At the same time, while providing gate DC bias through the self - biasing resistors Rf1 and Rf2, it can realize cross - negative feedback paths Rf1Cx2 and Rf2Cx1, adjust the amplitude and phase balance, and improve the gain and broadband matching.

[0040] The broadband feedback differential load network includes an inductive load Lo, first and second parallel resistors Rdi1 and Rdi2, a first output capacitor Cc1, and a second output capacitor Cc2. The inductive load Lo is connected between the two differential output terminals of the self - biasing feedback balanced differential output amplifier stage, and its center tap is connected to the power supply Vdd. The first and second parallel resistors Rdi1 and Rdi2 are in parallel with the inductive load and are respectively connected between the two differential output terminals of the self - biasing feedback balanced differential output amplifier stage and the center tap of the inductive load. The differential output terminals of the differential intermediate stage respectively output the final differential output signals of the broadband single - ended input differential amplifier through the first output capacitor Cc1 and the second output capacitor Cc2. The inductive load Lo and the first and second parallel resistors Rdi1 and Rdi2 adjust the bandwidth of the matching network. Figure 3 In the broadband feedback path shown, the second inductor Ls of the unbalanced single - ended to differential input amplifier stage is transformer - coupled with the inductive load of the broadband feedback differential load network to form a broadband feedback path. According to the transformer coupling, the in - phase and anti - phase selection and the input feedback form, the feedback path can be one or two.

[0041] The power supply Vdd provides the working voltage for each module circuit.

[0042] Figure 4 Shown is the comparison of the gain curves of the traditional broadband single - ended to differential amplifier and the broadband single - ended input differential amplifier circuit of the present invention. After testing and comparison, within the entire operating frequency range, the gain value of the present invention is higher than that of the traditional circuit. The broadband single - ended input differential amplifier circuit can improve the system gain while improving the bandwidth, and the maximum gain improvement is greater than 3.6 dB.

[0043] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A broadband single-ended input differential amplifier, characterized in that: The broadband single-ended input differential amplifier comprises an unbalanced single-ended to differential input amplifier stage, a self-biased feedback balanced differential output amplifier stage, a broadband feedback differential load network and a broadband feedback path; The unbalanced single-ended to differential input amplifier stage is the input stage circuit of the broadband single-ended input differential amplifier, which internally comprises two stages of cascaded reverse amplifiers to convert the single-ended input signal into a differential intermediate stage signal; The self-biased feedback balanced differential output amplifier stage is the output stage circuit of the broadband single-ended input differential amplifier, cascaded to the rear end of the unbalanced single-ended to differential input amplifier stage, further processes the differential intermediate stage signal and forms a final differential output signal; The broadband feedback differential load network is connected in parallel to the differential output end of the self-biased feedback balanced differential output stage, and the differential output signal is fed back to the unbalanced single-ended to differential input amplifier stage through the broadband feedback path to achieve broadband matching.

2. The broadband single-ended input differential amplifier according to claim 1, wherein: The unbalanced single-ended to differential input amplifier stage comprises a cascaded first reverse amplifier and a second reverse amplifier, the input end of the second reverse amplifier is connected to the output end of the first reverse amplifier, and the input end of the first reverse amplifier is connected to the input signal; the output end of the first reverse amplifier outputs a first path of differential intermediate-stage signals, that is, a signal inverted with the input signal, which is connected to the first differential input end of the self-biased feedback balanced differential output amplifier stage; the output end of the second reverse amplifier outputs a second path of differential intermediate-stage signals, that is, a signal in phase with the input signal, which is connected to the second differential input end of the self-biased feedback balanced differential output amplifier stage.

3. The broadband single-ended input differential amplifier according to claim 1, wherein: The self-biased feedback balanced differential output amplifier stage is connected to the differential intermediate stage signal, and the unbalanced differential intermediate stage signal is subjected to cross-input coupling processing to realize differential signal balanced processing. At the same time, the phase and gain amplitude are adjusted through self-biased feedback to optimize the differential signal balance and improve the signal gain and broadband matching; the self-biased feedback balanced differential output amplifier stage and the unbalanced single-ended to differential input amplifier stage share a DC bias.

4. The broadband single-ended input differential amplifier according to claim 2, wherein: The unbalanced single-ended to differential input amplifier stage comprises: An input inductor, a first transistor and a second transistor, a first input capacitor and a second input capacitor, a first inductor and a second inductor, and a first resistor and a second resistor; The input signal is connected to the gate terminal of the first transistor via the input inductor and the first input capacitor, the drain terminal of the first transistor outputs one of the differential intermediate-level signals, the gate terminal of the first transistor is connected to the first gate voltage via the first resistor, and the source terminal of the first transistor is grounded via the second inductor; The drain of the first transistor is also connected to the gate of the second transistor through a second input capacitor, and the gate of the second transistor is connected to a second gate voltage through a second resistor; the drain of the second transistor outputs another path of the differential intermediate-level signal, and the source of the second transistor is grounded.

5. The broadband single-ended input differential amplifier according to claim 3, characterized in that: The self-biased feedback balanced differential output amplifier stage comprises a third and a fourth transistor, a first and a second self-biasing resistor, and a first and a second feedback capacitor; The gate of the third transistor is connected to the source of the fourth transistor through the second feedback capacitor, and the gate of the fourth transistor is connected to the source of the third transistor through the first feedback capacitor. The source of the third transistor is the input of the self-biased feedback balanced differential output amplifier stage, and is connected to one of the output differential intermediate-stage signals; the source of the fourth transistor is the other input of the self-biased feedback balanced differential output amplifier stage, and is connected to the other output differential intermediate-stage signal. A first self-bias resistor is connected in series between the drain terminal and the gate terminal of the third transistor, and a second self-bias resistor is connected in series between the drain terminal and the gate terminal of the fourth transistor; The drain terminal of the third transistor and the drain terminal of the fourth transistor are differential output terminals of the self-biased feedback balanced differential output amplifier stage.

6. The broadband single-ended input differential amplifier according to claim 1, wherein: The broadband feedback differential load network comprises an inductive load, first and second parallel resistors, and first and second output capacitors; the inductive load is connected between the two differential output terminals of the self-biased feedback balanced differential output amplifier stage, and the middle tap thereof is connected to the power supply; the first and second parallel resistors are connected in parallel with the inductive load, and are respectively connected between the two differential output terminals of the self-biased feedback balanced differential output amplifier stage and the middle tap of the inductive load; the differential output terminals of the differential middle stage respectively output the final differential output signals of the broadband single-ended input differential amplifier through the first output capacitor and the second output capacitor; The inductive load and the parallel resistor are used to adjust the bandwidth of the matching network.

7. The broadband single-ended input differential amplifier according to claim 4 or 6, characterized in that: The second inductor of the unbalanced single-ended to differential input amplifier stage and the inductive load of the broadband feedback differential load network form a transformer coupling to form a broadband feedback path.

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