TW201820779A - High linearly WiGig baseband amplifier with channel select filter - Google Patents

Abstract

A circuit comprises a Sallen-Key filter, which includes a source follower that implements a unity-gain amplifier; and a programmable-gain amplifier coupled to the Sallen-Key filter. The circuit enables programmable gain via adjustment to a current mirror copying ratio in the programmable-gain amplifier, which decouples the bandwidth of the circuit from its gain settings. The programmable-gain amplifier can comprise a differential voltage-to-current converter, a current mirror pair, and programmable output gain stages. The Sallen-Key filter and at least one branch in the programmable-gain amplifier can comprise transistors arranged in identical circuit configurations.

Description

High linear wireless gigabit baseband amplifier with channel selection filter

The present invention generally relates to a circuit including a filter and a programmable gain amplifier, and more particularly, to a circuit that provides independent filter bandwidth control and gain.

This application claims the rights of US Provisional Patent Application No. 62 / 256,460, filed on November 17, 2015. The entire text of that case and all other external references cited herein are incorporated herein by reference.

The background note includes material that may be useful in understanding the invention. It is not an admission that any of the information provided herein is prior art or related to the invention claimed herein, or that any publication cited explicitly or implicitly is prior art.

The performance requirement of WiGig baseband signal processing system is three times the gain. Depending on the input signal level, sufficient gain needs to be generated to obtain the maximum signal-to-noise ratio (SNR) at the fundamental frequency output. It is also desirable to attenuate out-of-frequency signals for specific suppression levels and be able to accommodate input signals with high dynamic range while maintaining high linearity.

FIG. 1 is a schematic diagram of a fundamental frequency system in which the function of a filter is implemented by coupling a first dedicated amplifier in a closed-loop configuration to a second dedicated amplifier for providing a programmable gain. The first stage is a Sallen-Key filter with large input impedance and small output impedance. The input to this filter is through resistor R1, whose output couples resistor R2 and capacitor C3, and capacitor C3 is coupled to output Vout. Resistor R2 is coupled to capacitor C4 (which is connected to ground) and the positive input of the operational amplifier. This output Vout is directly coupled to the negative input of the operational amplifier to operate as a unity gain buffer. This operational amplifier provides high gain and can be used to form a second-order filter without using an inductor. In this case, the impedance of the Sallen-Key filter provides a low-pass filter. These filters can be designed as low-pass, high-pass, or band-pass filters. The second stage provides adjustable gain through the adjustable impedances Radj (1) and Radj (2) shown in Figure 1.

The following description contains information useful for understanding the present invention. This is not an admission that the information provided herein is prior art or related to the invention claimed herein, or that any publicly cited document, either expressly or implicitly, is prior art.

In one aspect of the invention, a circuit system includes a Sallen-Key filter and a programmable gain amplifier coupled thereto. The Sallen-Key filter includes a source follower implementing a unity gain amplifier. The programmable gain amplifier is used to decouple the circuit bandwidth from its gain setting by adjusting the current mirror replication ratio of the programmable gain amplifier to provide a programmable gain. The programmable gain amplifier may include a differential voltage-to-current converter, a current mirror pair, and a programmable output gain stage. In some aspects, the circuit is intended to operate as a low-pass filter, a high-pass filter, or a band-pass filter.

In another aspect, a circuit includes a Sallen-Key filter coupled with a programmable gain amplifier, wherein the circuit includes a source follower within the Sallen-Key filter and includes a first circuit configuration A first complex transistor within; and at least one branch in the programmable gain amplifier, including at least one second complex transistor disposed in at least one second circuit configuration, the at least second circuit configuration Same configuration as this first circuit. In some aspects, the first and at least second complex transistors have the same cell device size and current density. The circuit may have the same array in a manufacturing layout including unit devices. Methods for making such circuits and other circuits are disclosed herein.

Another aspect provides a way to avoid linearity from being affected by the operating region of the transistor in the amplifier of the Sallen-Key filter. The method includes using a source follower in the Sallen-Key filter to provide unity gain, the source follower including an active device and a load device; and selecting a direct current of the input signal to the Sallen-Key filter ( DC) level to ensure that there is sufficient margin in at least one of the load device and the current mirror pair device as a programmable amplifier.

As used herein and throughout the scope of the subsequent application, unless the context clearly dictates otherwise, "a," "an," and "the" include plural references. Moreover, as used herein, the meaning of "中" includes "中" and "上" unless the context clearly indicates otherwise.

The range of values listed here is intended only as a shorthand method for individually referring to each individual value falling within the range. Unless otherwise indicated herein, each individual value is included in this specification as if it were listed here individually. Unless otherwise stated herein, or clearly contradicted by context, all methods described herein can be performed in any suitable order. Any and all examples, or exemplary language (eg, "such as") used with respect to certain aspects herein are intended merely to better illuminate the invention and do not limit the scope of the invention as claimed. No language in the description should be construed as any unsolicited element necessary to implement the invention.

Groups of alternative elements or aspects of the invention disclosed herein should not be construed as limiting. Each group component can be talked about separately and requested separately or in any combination with other components of the group or other elements visible here. For convenience and / or patentability, a group may cover or omit one or more of these components. When there is any such coverage or omission, the description herein is deemed to include the modified group, thus conforming to the written description of all Marcusi groups in the scope of the attached application.

The detailed description given below in conjunction with the accompanying drawings is intended to describe various aspects of the invention, and is not intended to explain the only aspects of practicing the invention. The detailed description includes specific details for the purpose of providing a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In some cases, to avoid obscuring the concept of the present invention, conventional structures and elements are presented in block diagram form.

Each aspect of the invention may represent a single combination of elements of the invention, and the invention is deemed to include all possible combinations of the disclosed elements. Therefore, if one aspect includes elements A, B, and C and the second aspect includes elements B and D, the present invention is considered to include other remaining combinations of A, B, C, or D even if not explicitly disclosed.

As used herein, unless the context otherwise requires, the term "coupled ..." is intended to include direct coupling (where two elements that are coupled to each other are in contact with each other) and indirect coupling (where at least one additional element is located between the two elements) between). Therefore, the terms "coupled ..." and "coupled with" have the same meaning.

Figure 2 is a circuit diagram illustrating a filter and amplifier constructed in accordance with one aspect of the present invention. A pair of signal input nodes (INP) and a pair of signal output nodes (OUTN) are provided. Transistors (such as field effect transistors) are represented by M1-M8 and M1b-M8b. The resistance is represented by R0, R1-R3, and R1b-R3b. Capacitors are represented by C1, C2, C1b, and C2b. The capacitance of C2 and C2b can be adjusted (for example, programmable). The power supply voltage, transistor base voltage, and ground are represented by symbols commonly used in the art.

In the circuit structure shown in Fig. 2, M2, M2b, M5 and M5b provide the function of source follower. A source follower amplifier includes two serially stacked devices coupled between a supply voltage VDD and ground. One of the first devices (ie, the active device) converts the input signal and the second device (ie, the load device). Provide a load. The load device is biased by a DC bias voltage. The output signal of the source follower is in phase with the input signal, and the voltage gain is approximately 0 dB and linear.

The low power supply voltage used in the integrated circuit limits the voltage margin (ready-to-use output signal swing). To alleviate the margin problem, an active current source load can be used. For example, the load device may provide a controlled current load to the active device driven by an input. Therefore, the load device provides a DC bias to operate the source follower.

The components R1, R2, C1, C2 and M5 operate as a Sallen-Key filter. Therefore, according to one aspect of the present invention, the source follower is included in the design of the Sallen-Key filter. The operational amplifier in the conventional Sallen-Key filter in Figure 1 limits the high-frequency operation of the filter and often results in high power consumption. The source follower can significantly extend the high frequency operating range of the filter while achieving low power consumption. This source follower has similar input / output characteristics as an op amp. The operational amplifier presents infinite input impedance, good current drive, and small output impedance at its input and output. Similarly, this source follower has the contribution of high input impedance, good current drive, and low output impedance at its input and output.

The elements M2, M2b, and R0 convert the differential voltage between the voltages Vx and Vxb shown in the circuit diagram into a differential current through the transistors M1 and M1b. The transistor pair M1, M7 and M1b, M7b provides a current mirror pair with a gain equal to the device ratio between M7 and M1. The elements M7 and R3 constitute a first output gain stage, and the elements M7b and R3b constitute a second output gain stage, wherein the first and second output gain stages convert an input differential current into an output differential voltage.

The overall differential gain of this input signal is: (1) The transfer function of the filter is: (2) of which , And .

According to some aspects of the disclosed, the circuit disclosed herein may be used in the fundamental frequency processing of wideband signals, such as those used in the WiGig standard. This can reduce power consumption compared to conventional circuits. For example, the closed-loop bandwidth of the amplifier in the conventional Sallen-Key filter needs to be comparable to the filter bandwidth. This series usually requires high power consumption, especially in the case of WiGig signals. However, in all aspects disclosed herein, consistency gain is achieved by the source follower system.

In some aspects of the revealer, linearity can be improved. In the conventional Sallen-Key filter design, linearity depends on the operating region of the transistor in the filter's amplifier. The ideal operating region for these transistors is the saturation region, which has sufficient drain-to-source voltage. For large input signals, the transistor headroom is reduced. Therefore, the open-loop gain of the amplifier is reduced, and the assumption that the closed-loop gain of the amplifier is consistent is broken, which results in a decrease in linearity.

In some aspects of the revealer, since the source follower (M5 and M5b) of the Sallen-Key filter provides consistent gain, the only marginal effect is limited to transistors M4 and M4b, which can be easily transmitted through Set the input to a higher DC level. Similarly, for a programmable gain amplifier, when the input is set to a sufficiently high DC level, the transistors M1 and M7 can be guaranteed to have sufficient margin, which makes the current copy from M1 to M7 independent of the input signal level. influences. At the output, as the transistor M8 operates as a cascade device, the margin can be slightly compressed without affecting current replication (and linearity).

The circuit shown in Figure 2 can provide independent filter bandwidth and gain control. In conventional filter-amplifier circuits, the bandwidth of the programmable gain amplifier is also a function of the gain setting. In order to have independent bandwidth and gain control (that is, the bandwidth is controlled only by the Sallen-Key filter, and the gain is controlled only by the programmable gain amplifier), the programmable gain amplifier sets the frequency for the worst-case gain setting. The width must be large enough to avoid affecting the overall bandwidth, resulting in a suboptimal design that will cause high power consumption. In contrast, in the circuit shown in Figure 2, the programmable gain can be achieved by the current mirror replication ratio (W7 // W1) and the resistance ratio (R3 / R0). This system can achieve high bandwidth without significant power consumption. Therefore, according to certain aspects of the presenter, independent filter bandwidth and gain control can be achieved without increasing the power consumption budget.

Certain aspects of the disclosed circuit design can facilitate the fabrication of circuits that include a Sallen-Key filter coupled to a programmable gain amplifier. The similarity of the circuit structure between the amplifier in the Sallen-Key filter and the programmable gain amplifier (for example, branch M6, M5, M4, branch M3b, M2, M1, and branch M8, M7) can be Facilitate layout, simplify design, reduce manufacturing costs, and / or improve chip functionality. By selecting the transistor size to provide the same unit device size and current density, the layout can be highly compact and provide the same array of unit devices, which can mitigate some layout-related effects. Accordingly, certain aspects of the disclosed include the design and manufacture of integrated circuits, which may include methods, devices, and programmable control systems for manufacturing integrated circuits in accordance with the design aspects disclosed herein.

While Figure 2 illustrates a low-pass implementation of a circuit, the new aspects disclosed herein can be used in alternative circuit configurations and can be used with any type of filter characteristics suitable for fundamental, intermediate and / or radio frequency processing. .

As an example, by replacing capacitors R1, R2, R1b, and R2b with capacitors, and replacing resistors C1, C2, C1b, and C2b with resistors, a high-pass implementation can be provided. The resulting high-pass bandwidth is .

On the other hand, by cascading a high-pass filter and a low-pass filter, a band-pass application can be realized. For example, an AC coupling capacitor may be implemented following the low-pass filter. It will be apparent to those skilled in the art that alternative filters designs and applications for these circuits and related circuits can be provided based on the teachings disclosed herein.

Bias currents from M6, M6b, M3, and M3b will affect circuit performance. The large bias current will make the devices M5 and M2 have large transconductance gm, which reduces the output impedance of the source follower stage to obtain the same gain. However, for a given current density, an excessive bias current usually results in a larger device size. This system generates a large capacitive load at the output of the Sallen-Key filter and the output of the source follower M2, thereby reducing the bandwidth. Therefore, circuits designed according to the aspects disclosed herein can make these trade-offs, for example, to produce a circuit with the best design for the above parameters.

FIG. 3 is a flowchart describing steps that can be performed in accordance with aspects of the disclosed subject matter. These steps may include methods to avoid linearity from being affected by the operating region of the transistor in the Sallen-Key filter amplifier. A first step 301 includes using a source follower in a Sallen-Key filter. The source follower includes an active device and a load device, and can provide consistent gain. A second step 302 includes at least one transistor in a filter-amplifier circuit (such as a load device and a device for centering a current mirror used as a programmable amplifier) to determine the required margin. A third step 303 includes selecting a DC level of the input signal of the Sallen-Key filter to ensure a sufficient margin in the at least one transistor.

FIG. 4 is a flowchart describing a method structured according to one aspect of the presenter. As described above for FIG. 2, the amplifier in the Sallen-Key filter and the programmable gain amplifier (for example, branch M6, M5, M4, branch M3b, M2, M1, and branch M8, M7) The circuit structure similarity between them can facilitate layout, simplify design, reduce manufacturing costs, and / or improve chip functionality.

A first step 401 of a method for manufacturing an integrated circuit includes using a transistor layout commonly used in a Sallen-Key filter and at least one programmable gain amplifier. A second step 402 includes designing the Sallen-Key filter and a programmable gain amplifier (and, optionally, other circuits and / or circuit portions) to include the transistor layout. This can provide a circuit design for the Sallen-Key filter and the programmable gain amplifier. A third step 403, which may optionally before step 402, includes selecting the size of the transistor in the layout to provide the same unit device size and current density. Steps 402 and / or 403 may further include designing the layout to be highly compact and providing the same array of unit devices that can mitigate the effects of the layout. Based on the resulting circuit design, the Sallen-Key filter and the programmable gain amplifier 404 are manufactured.

The method constructed according to some aspects of the disclosed can provide integrated circuit design of the circuit configuration disclosed herein. In some aspects, the method is used to manufacture integrated circuits in accordance with the designs disclosed herein. The methods disclosed herein may include a programmable system for designing and / or manufacturing integrated circuits in accordance with the aforementioned design aspects.

It should be noted that any language involving a method may be executed by any suitable combination of computing devices including servers, interfaces, systems, databases, agents, peers, engines, modules, controllers, or alone Other types of computing devices operating or operating in conjunction. It should be understood that the computing device includes a process for executing software instructions stored on a tangible, non-transitory computer-readable storage medium (eg, hard disk drive, solid state drive, RAM, flash memory, ROM, etc.) Device. The software instructions preferably construct the computing device to provide the functions, responsibilities, or other functions of the disclosed circuits and methods disclosed herein.

It will be apparent to those skilled in the art that many modifications can be made without departing from the inventive concepts herein except those already described herein. Therefore, the subject matter of the present invention must be in accordance with the spirit of the scope of the attached application, and is not subject to other restrictions. In addition, when explaining the scope of the specification and application, all terms should be interpreted in the broadest possible manner consistent with the text. In particular, the terms "including" and "comprising" when referring to elements, components or steps in a non-exclusive manner should be construed to mean having or adopting the elements, components or steps in question, or in connection with other elements, components or steps Or a combination of steps. Where the specification and the scope of the application speak of at least one of the things selected from the group consisting of A, B, C ... and N, it should be construed as the need to select only one element from the group, not A plus N, or B Add N and so on.

[Prior art]

R1, R2‧‧‧ resistors

C3, C4‧‧‧ capacitors

Vout‧‧‧output

Radj (1), Radj (2) ‧‧‧Adjustable impedance

[Embodiment]

INP‧‧‧Input node

OUTN‧‧‧Signal output node

M1-M8, M1b-M8b‧‧‧Transistors

R0, R1-R3, R1b-R3b‧‧‧ resistance

C1, C2, C1b, C2b‧‧‧ capacitors

VDD‧‧‧ supply voltage

Vx, Vxb‧‧‧Voltage

The flowchart described in the method of the present invention includes "processing blocks" or "steps", which may represent computer software instructions or instruction sets. Alternatively, the processing block or step may represent a step performed by a functionally equivalent circuit, such as a step performed by a digital signal processor or a special application integrated circuit (ASIC). A flowchart does not describe the syntax of any particular programming language. Rather, the flowchart illustrates the functional information required by a person of ordinary skill in the art to fabricate circuits or generate computer software for performing the processing required by the present disclosure. It should be noted that many conventional program elements are not presented, such as the initialization of loops and variables, and the use of temporary variables. Those of ordinary skill in the art should appreciate that, unless otherwise indicated herein, the specific order of the steps described is merely illustrative and may vary. Unless otherwise noted, the steps described below are out of order, which means that the steps can be performed in any convenient or desired order.

FIG. 1 is a circuit block diagram in which the function of the filter is implemented by coupling a first dedicated amplifier configured to provide a programmable gain through a first dedicated amplifier in a closed loop configuration.

Figure 2 is a circuit diagram illustrating a filter and amplifier constructed in accordance with an aspect of the present invention.

FIG. 3 is a flowchart illustrating steps of a method performed according to an aspect of the present invention.

FIG. 4 is a flowchart illustrating steps of a method performed according to an aspect of the present invention.

Claims (16)

A circuit includes: a Sallen-Key filter including a source follower implementing a single gain amplifier; and a programmable gain amplifier coupled to the Sallen-Key filter, the circuit is used to adjust the programmable gain by The amplifier's current mirror duplicates the ratio and decouples the circuit bandwidth from its gain setting to provide a programmable gain. The circuit described in item 1, wherein the programmable gain amplifier includes a differential voltage-current converter, a current mirror pair, and a programmable output gain stage. The circuit described in item 1 is used to operate as at least one of a low-pass filter, a high-pass filter, and a band-pass filter. The circuit according to item 1, wherein the source follower includes a first complex transistor disposed in a first circuit configuration, and at least one circuit of the programmable gain amplifier includes an At least one second complex transistor in at least one second circuit configuration, the at least second circuit configuration is the same as the first circuit configuration. The circuit according to item 4, wherein the first and the at least second complex transistors have the same unit device size and current density. The circuit described in item 1 includes an identical array with a manufacturing layout including unit devices. A method for preventing linearity from being affected by a transistor operating region in an amplifier of a Sallen-Key filter, comprising: using a source follower in the Sallen-Key filter to provide unity gain, the source follower including a Active device and a load device; and the DC level of the input signal selected to the Sallen-Key filter to ensure that at least one of the load device and the current mirror pair device as a programmable amplifier has sufficient margin . The method according to item 7, wherein the programmable gain amplifier includes a differential voltage-current converter and a programmable output gain stage. The method according to item 7, wherein the Sallen-Key filter is used to operate as at least one of a low-pass filter, a high-pass filter, and a band-pass filter. The method according to item 7, wherein the source follower includes a first complex transistor disposed in a first circuit configuration, and at least one circuit of the programmable gain amplifier includes an At least one second complex transistor in at least one second circuit configuration, the at least second circuit configuration is the same as the first circuit configuration. The method according to item 10, wherein the first and the at least second complex transistors have the same unit device size and current density. The method as recited in item 10, wherein each of the source follower and the programmable gain amplifier includes an identical array with a manufacturing layout including unit devices. A method for manufacturing an integrated circuit includes: designing a transistor layout including an array of unit devices, the transistor layout being common to a Sallen-Key filter and at least one programmable gain amplifier; selecting the circuit The size of the transistor in the crystal layout to provide the same unit device size and current density; produce a design of the Sallen-Key filter and the programmable gain amplifier each including the transistor layout; and manufacture the design based on the design Sallen-Key filter and the programmable gain amplifier. The method described in item 13 includes designing the transistor layout to be compact and provide the same array of unit devices. The method according to item 13, wherein the programmable gain amplifier includes a differential voltage-current converter, a current mirror pair, and a programmable output gain stage. The method according to item 13, wherein the integrated circuit is used to operate as at least one of a low-pass filter, a high-pass filter, and a band-pass filter.