KR100828187B1 - Amplifier using common inductor - Google Patents

Abstract

An amplifier using a common inductor is provided to reduce a size of the chip and to minimize a parasitic component such as a parasitic capacitance by using the common inductor. An amplifier using a common inductor comprises an input terminal(601), an impedance matching unit(650), an amplifying unit(652), and a negative feedback unit(654). An input signal is inputted to the input terminal. The impedance matching unit matches an input frequency of the input signal with an equal output frequency using a first inductor(606). The amplifying unit amplifies the impedance-matched signal. The negative feedback unit performs a negative feedback of a part of the output signal from the amplifying unit, and removes a high frequency component of the resultant signal using the first inductor.

Description

Amplifier using common inductor

1 shows a noise and impedance simultaneous matching circuit according to the prior art;

2 is a diagram illustrating an impedance matching circuit using a negative feedback according to the prior art.

3 is a diagram illustrating a noise and impedance simultaneous matching circuit to which a negative feedback technique according to the related art is applied.

4 shows an example of an inductor used in a CMOS process.

5 illustrates a wireless communication system in accordance with a preferred embodiment of the present invention.

6 is a diagram illustrating a noise and impedance simultaneous matching circuit to which a negative feedback technique is applied according to an exemplary embodiment of the present invention.

7 is an equivalent circuit diagram of a low noise amplifier to which the matching circuit according to FIG. 6 is applied.

8 is a graph of a gain curve of a low noise amplifier according to the present invention.

9 is a graph of the insertion loss curve of the low noise amplifier according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier using a common inductor, and more particularly, to an amplifier capable of achieving high gain while simultaneously reducing noise and impedance while matching a low inductor in a low noise amplifier.

A typical wireless communication system has an amplifier for amplifying the signal externally. Recently, wireless standards such as WCDMA, CDMA2000, WIBRO, Bluetooth, Zigbee, WLAN, and the like use a broadband such as 1.8 to 2.5 G㎐. Therefore, a low noise amplifier (LNA) is required for the development of a receiver supporting various frequency bands as described above.

In a wireless communication system, a low noise amplifier (LNA) is a circuit that amplifies a weak signal received from an antenna without noise. The low noise amplifier is located at the front of the receiver. Since the noise figure (NF) of the low noise amplifier determines the performance of the receiver as a whole, it eliminates the noise of the received signal without distortion of the signal. Impedance matching of the output stage is required.

In addition, with the development of wireless communication systems, there is a need for a low noise amplifier capable of impedance matching over a wide band such as ultra-wideband (UWB).

1 is a diagram illustrating a noise and impedance simultaneous matching circuit according to the prior art. 1 shows a circuit for matching impedance while simultaneously removing noise in a narrow band as a common gate structure.

The circuit shown in FIG. 1 is composed of a plurality of inductors L _g , L _s and capacitors C _in , C _out and a plurality of CMOS transistors M ₁ , M ₂ .

Here, the inductor L _g connected to the gate terminal of the first MOS transistor M ₁ removes the imaginary component of impedance appearing in the input signal through an inductance sum with the inductor L _s connected to the M ₁ transistor source terminal. It plays a role.

On the other hand, the parasitic capacitance (C _gs ) appearing in the first MOS transistor (M ₁ ) and the transconductance (g _m ) value connected in parallel is a combination of the inductance components of the inductor (L _s ) of the source terminal to improve the impedance of the real part. By generating, matching at a specific frequency is possible.

In this case, since no resistance component is inserted into the input terminal, low noise may be simultaneously realized during impedance matching. However, the technique shown in FIG. 1 has a problem that matching is possible only in narrow band.

On the other hand, the negative feedback circuit is a structure in which a part of the output is connected to the input and the past input value affects the current input value. In terms of gain, the negative feedback circuit has a low impedance because the MOS transistor and the negative feedback structure are connected in parallel. However, since the transconductance (g _m ) of the MOS transistor is smaller than that of a general cascode or common source structure, a large output gain cannot be obtained, but it has characteristics of improving stability and band characteristics.

This is because there is an effect that the band is extended as the output gain of the vertex is lower than when there is no negative feedback circuit. Therefore, the negative feedback structure provides very advantageous characteristics in terms of bandwidth as well as stability in the broadband amplifier circuit.

2 is a diagram illustrating an impedance matching circuit using a negative feedback according to the prior art.

Referring to FIG. 2, the negative feedback circuit is connected in series between the gate terminal of the first MOS transistor M ₁ and the drain terminal of the second MOS transistor M ₂ , and has a capacitor C _f and a resistor R _f . And an inductor L _f .

In this case, a predetermined bias voltage is applied to the gate terminals of the first and second MOS transistors, and a predetermined power supply voltage V _dd is applied to the drain terminal to excite the output signal to the output load Z _n .

3 is a diagram illustrating a noise and impedance simultaneous matching circuit to which a negative feedback technique according to the related art is applied.

In FIG. 3, (a) shows a negative feedback circuit, and (b) shows a circuit applied to simultaneous noise and impedance matching of FIG.

However, when the above circuit is used, stability and band characteristics may be improved and high gains may be obtained. However, many inductors may be used.

That is, the amplifier circuit according to FIG. 3 includes an inductor L _fA which gives an impedance to high frequency in the negative feedback circuit, and two inductors L _gA and L _sA that are applied to the simultaneous matching of noise and impedance. Two inductors are required.

Figure 4 shows an inductor of 4.5 turns used in a 0.18 mu m CMOS process. Inductors used for input matching vary according to frequency and impedance response, but inductors of 200 mu m or more in width and length are inserted as in the example of the inductor of FIG.

This has a lot of occupancy compared to the size of the entire circuit implemented through the layout.

In general, broadband amplifiers applied to UWB (Ultra Wide Band) have a chip area of 1 mm 2 or more in a CMOS process. This is due to the insertion of many inductors, such as load inductors for gain of high frequency and inductors required for wideband and high frequency response.

As such, the overall layout size is determined according to the number of inductors used in the circuit. When three inductors are used for input matching, as shown in FIG. 3, performance decreases due to an increase in cost and a parasitic component increase due to an increase in chip area. do.

The performance degradation due to parasitic component increase is due to the extension of the signal path of the inductor, which takes up a relatively large area. Therefore, it is necessary to reduce the number of inductors used to reduce costs and prevent performance degradation of the circuit.

In order to solve the problems of the prior art as described above, the present invention proposes an amplifier capable of impedance matching at low noise while having a small number of inductors.

According to a preferred embodiment of the present invention to achieve the above object, an amplifier for amplifying an input signal with low noise, comprising: an input terminal for receiving the input signal; An impedance matching unit for matching an input frequency of the input signal to the same output frequency by using a first inductor; An amplifier for amplifying the impedance matched signal; And a negative feedback part performing negative feedback on a part of the amplification part output signal and removing a high frequency component of the negative feedback signal by using the first inductor.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and, unless expressly defined in this application, are construed in ideal or excessively formal meanings. It doesn't work.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the same reference numerals will be used for the same means regardless of the reference numerals in order to facilitate the overall understanding.

5 is a diagram illustrating a wireless communication system according to an exemplary embodiment of the present invention.

FIG. 5 illustrates a wireless communication signal receiving system. As shown in FIG. 5, the wireless communication system includes an antenna 500, a band selection filter 502, a low noise amplifier 504, an image removal filter 506, RF down mixer 508, RF local oscillator 510, phase locked loop 512, channel select filter 514, IF amplifier 516, IF down mixer 518 and IF local oscillator 520. Can be.

The antenna 500 receives an electromagnetic wave signal in the air and converts the signal into an electrical signal on a conductive line.

The signal received through the antenna 500 includes a number of frequency components corresponding to noise. The band select filter 502 performs band pass filtering to amplify only a desired frequency band.

If there are multiple channels, the band select filter 502 passes in-band. In this case, the duplexer may serve as a band select filter when the same antenna 500 is used.

The low noise amplifier 504 amplifies the signal output from the band pass filter 502. In this case, the low noise amplifier 504 allows the signal to be amplified while maximally suppressing amplification to noise.

The low noise amplifier 504 according to the present invention may be applied to a wide band and may include a noise and impedance simultaneous matching circuit to which a negative feedback technique is applied. In this case, since the matching circuit uses a common inductor, the matching circuit reduces chip area while having stability and band characteristics.

This will be described in detail with reference to FIGS. 6 to 9.

The Image Reject Filter 506 once again performs bandpass filtering to prevent lethal image frequencies from being transmitted to the mixer 508 below among the signals amplified by the low noise amplifier 504. In addition, the image removal filter 506 removes the spurious frequency and separates the high frequency (RF) stage and the intermediate frequency (IF) stage to improve the stability of the receiving system.

The RF down mixer 508 performs a function of frequency downconverting the low noise amplified RF signal to the IF band. In this case, the RF local oscillator 510 supplies a local oscillation (LO) frequency for frequency synthesis of the RF down mixer 508. In the case of communication requiring channel selection, channel selection can be made by changing the LO frequency.

A phase locked loop (PLL) 512 allows the output frequency of the RF local oscillator 510 to be locked at a constant frequency without shaking. In addition, by precisely adjusting the voltage of the voltage controlled oscillator (VCO) used in the RF local oscillator 510 through a control signal, the output frequency of the RF local oscillator 510 is moved to a desired frequency and fixed.

Signals converted to the intermediate frequency IF may include all of the various channels. The channel select filter 514 selects only a desired channel through band pass filtering.

Since the low noise amplifier 504 of the RF stage cannot sufficiently amplify the weak received signal, the IF amplifier 516 may perform signal amplification on the signal filtered through the channel.

The IF down mixer 518 removes the carrier frequency through down-conversion mixing and converts to a baseband, which is a frequency band in which the original signal is contained.

IF local oscillator 520 supplies the IF down mixer 518 with an LO frequency for converting the intermediate frequency into a baseband signal.

Hereinafter, the low noise amplifier according to the present invention used for low noise amplification in the wireless communication system will be described in detail.

6 is a diagram illustrating a noise and impedance simultaneous matching circuit to which a negative feedback technique is applied according to an exemplary embodiment of the present invention.

6 relates to a circuit included in a low noise amplifier according to the present invention, and is a circuit capable of impedance matching with low noise in a wide band.

As shown in FIG. 6, the matching circuit according to the present invention includes a plurality of capacitors C _in , C _f , C _{out ,} 600 to 604, a first inductor L _{g ,} 606, a second inductor L _{s ,} 608, a plurality of MOS transistors M ₁ , M _{2 ,} 610 _, 612, and output loads Z _{D ,} 614.

According to the present invention, the first inductor 606 is an imaginary component of impedance as an inductance sum with a second inductor 608 connected to the source terminal of the first MOS transistor 610 with respect to the signal input from the input terminal 601. Remove it.

The parasitic capacitance (C _gs ) appearing in the first MOS transistor 610 and the transconductance (g _m ) value appearing in parallel thereto generate an impedance of the real part by a combination of inductance components of the second inductor 608.

The first inductor 606, the second inductor 608, and the first MOS transistor 610 correspond to the impedance matching unit 650 in that an imaginary part of impedance is removed and an impedance of a real part is generated.

On the other hand, the second MOS transistor 612 with the bias voltage applied to the gate terminal corresponds to the amplifier 652 for amplifying the input signal. In addition _, a negative feedback part 654 including capacitors C _{f and} 604 and resistors R _{f and} 616 is connected to the drain terminal of the second MOS transistor 612 for wideband characteristics.

Here, the capacitor 604 serves to prevent the DC bias across the capacitor, the resistor 616 has a value of several hundred ohms to several kiloohms to determine the amount of negative feedback signal.

Meanwhile, in the related art, the negative feedback unit includes a separate inductor to impart an impedance to the high frequency component, but according to the present invention, the first inductor 606 performs the same function as described above to remove the imaginary subcomponent of the input signal. do.

That is, according to the present invention, the first inductor 606 is used as a common inductor of the impedance matching unit 650 and the negative feedback unit 654.

Experimentally, when using the first inductor as a common inductor as in the present invention, it was possible to reduce the chip area by about 0.06 mm ² compared to the conventional CMOS low noise amplifier.

In the case of providing the first inductor 606 to be commonly used in the impedance matching and the negative feedback path, it is possible to solve the problem of providing a plurality of inductors associated with the matching of the wideband frequency, and to increase the cost and the signal path as the chip area increases. It is possible to suppress the problem of increased parasitic components.

7 is an equivalent circuit diagram of a low noise amplifier to which the matching circuit of FIG. 6 is applied.

FIG. 7 illustrates a case in which a gain circuit 730 for increasing amplification gain is connected to a matching circuit 630 using the common inductor (first inductor 606) shown in FIG. 6 in a cascode form.

As shown in FIG. 7, the matching circuit 630 having the common inductor has the configuration shown in FIG. 6, and the output of the capacitor C _is 602 through the amplifier 652 of the matching circuit _is third. Through the inductor (L _is , 700) _is input to the gate terminal of the third MOS transistor 702 of the gain circuit.

In this case, the signal input to the matching circuit 630 may be represented by an equivalent circuit of V _b1 and R _b1 , and the signal input to the gain circuit 730 may be represented by an equivalent circuit of V _b2 and R _b2 .

Here, the third inductor 700 located between the matching circuit 630 and the gain circuit 730 performs a function of blocking a high frequency band other than the required bandwidth because the third inductor 700 is in resonance with the parasitic capacitance of the third transistor 702. do. Accordingly, the blocking characteristic of a specific band can be improved.

The fourth MOS transistor 704 combines the third MOS transistor 702 and the third inductor 700 to amplify a signal having a specific band cut off to a desired gain bandwidth.

On the other hand, the resistors R _D1 , R _D2 , 618, 708 located in the loads Z _D1 , Z _{D2 of the} matching circuit 630 and the gain circuit 730 have flat characteristics in all bands instead of slightly lowering the gain.

8 is a graph of a gain curve of a low noise amplifier according to the present invention, and FIG. 9 is a graph of an insertion loss curve of a low noise amplifier according to the present invention.

As can be seen from the gain curve graph of FIG. 8, when the common inductor according to the present invention is used, the gain decreases due to the negative feedback path while the gain flatness is very excellent. On the other hand, the insertion loss graph of Figure 9 shows that the negative feedback method and the noise and impedance co-matching method according to the present invention generates two resonances, resulting in a wide bandwidth input matching.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

As described above, according to the present invention, since the common inductor is used to remove the high frequency component in the negative feedback path along with the removal of the impedance imaginary component in the matching circuit, the chip area of the low noise amplifier can be reduced. .

In addition, according to the present invention, since the signal path is reduced by using a common inductor, parasitic components (for example, parasitic capacitance) may be minimized.

Claims (7)

An amplifier for amplifying an input signal with low noise, An input terminal for receiving the input signal; An impedance matching unit for matching an input frequency of the input signal to the same output frequency by using a first inductor; An amplifier for amplifying the impedance matched signal; And And a negative feedback part performing negative feedback on a part of the amplification part output signal and removing high frequency components of the negative feedback signal using the first inductor. The method of claim 1, The impedance matching unit, A first MOS transistor having a gate terminal connected to the first inductor; And And a second inductor connected to the source terminal of the first transistor. The method of claim 2, And the amplifier includes a second MOS transistor having a source terminal connected to a drain terminal of the first MOS transistor and a drain terminal connected to the negative feedback unit. The method of claim 1, The negative feedback part of the capacitor to prevent the DC bias applied to both ends; And And a resistor for determining the amount of the negative feedback signal. The method of claim 1, And a gain circuit connected to the output of the amplifier and via a third inductor. The method of claim 5, The gain circuit, A third MOS transistor having a gate end coupled to the third inductor, wherein parasitic capacitance between the gate end and the source end of the third MOS transistor resonates with the third inductor; And And a fourth MOS transistor for secondarily amplifying the signal output from the amplifier. The method of claim 6, And an resistor providing a flatness characteristic to one end of the amplifier and the fourth MOS transistor.

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