Low noise amplifier and method of operating low noise amplifier

Abstract

A low noise amplifier and a method of operating a low noise amplifier are provided. The low noise amplifier includes: a first transistor configured to amplify an input radio frequency (RF) signal of a first frequency band and configured to receive a first bias voltage; a second transistor configured to amplify an input RF signal of a second frequency band and configured to receive a second bias voltage; a third transistor configured to amplify an output RF signal of the first transistor and configured to receive a third bias voltage; and a fourth transistor configured to amplify an output RF signal of the second transistor and configured to receive a fourth bias voltage. In a first mode of operation, the second bias voltage and the fourth bias voltage may be set to turn-off voltage levels, and in a second mode of operation, the first bias voltage and the third bias voltage may be set to turn-off voltage levels.

Description

Technical Field

[0001] The following disclosure relates to a low-noise amplifier and a method of operating a low-noise amplifier. Background Art

[0002] A low-noise amplifier (LNA) may be included in a receiving end of a wireless communication device and is an element that amplifies a weak signal received through an antenna into a strong noise-resistant signal. The low-noise amplifier is an important circuit that determines the noise figure of the receiving end.

[0003] Generally, a band selection switch may be located at the front end of the low-noise amplifier. The band selection switch switches multiple radio frequency (RF) signals (each RF signal having multiple frequency bands) and sends the RF signals to the low-noise amplifier. In an example, it may be beneficial for the low-noise amplifier to have a multi-band operation for processing input RF signals having different frequency bands.

[0004] However, the band selection switch may cause insertion loss, which may increase the overall noise figure.

[0005] The above information is presented as background art information only to assist in understanding the present disclosure. The above description should not be construed as these contents belonging to the prior art of the present disclosure. Summary of the Invention

[0006] This Summary of the Invention is provided to introduce selected concepts in a simplified form and these concepts are further described in the Detailed Description below. This Summary of the Invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to help determine the scope of the claimed subject matter.

[0007] In one general aspect, a low-noise amplifier includes: a first transistor configured to amplify an input radio frequency (RF) signal in a first frequency band and configured to receive a first bias voltage; a second transistor configured to amplify an input RF signal in a second frequency band and configured to receive a second bias voltage; a third transistor configured to amplify the output RF signal of the first transistor and configured to receive a third bias voltage; and a fourth transistor configured to amplify the output RF signal of the second transistor and configured to receive a fourth bias voltage, wherein, in a first operation mode, the second bias voltage and the fourth bias voltage are set to a cut-off voltage level, and wherein, in a second operation mode, the first bias voltage and the third bias voltage are set to a cut-off voltage level.

[0008] In the first operation mode, the first bias voltage and the third bias voltage may be set to a conduction voltage level, and in the second operation mode, the second bias voltage and the fourth bias voltage may be set to a conduction voltage level.

[0009] In the first operation mode, the first transistor and the third transistor may be configured to perform an amplification operation, and the second transistor and the fourth transistor may not perform an amplification operation. In the second operation mode, the second transistor and the fourth transistor may be configured to perform an amplification operation, and the first transistor and the third transistor may not perform an amplification operation.

[0010] When an input RF signal in the first frequency band is input, the first operation mode may be executed, and when an input RF signal in the second frequency band is input, the second operation mode may be executed.

[0011] The input RF signal in the first frequency band and the first bias voltage may be applied to a control terminal of the first transistor, and the input RF signal in the second frequency band and the second bias voltage may be applied to a control terminal of the second transistor.

[0012] The third bias voltage may be applied to a control terminal of the third transistor, and the output RF signal of the first transistor may be applied to a first terminal of the third transistor. The fourth bias voltage may be applied to a control terminal of the fourth transistor, and the output RF signal of the second transistor is applied to a first terminal of the fourth transistor.

[0013] The low-noise amplifier may further include: a first inductor connected between a first terminal of the first transistor and the ground; and a second inductor connected between a first terminal of the second transistor and the ground.

[0014] The low-noise amplifier may further include a third inductor, the inductor including a first end connected to a power supply voltage and a second end connected to a second terminal of the third transistor and a second terminal of the fourth transistor.

[0015] The inductance value of the third inductor may vary according to the first operation mode and the second operation mode.

[0016] In one general aspect, a method of operating a low-noise amplifier (the low-noise amplifier including a first transistor that amplifies an input radio frequency (RF) signal in a first frequency band and a second transistor that amplifies an input RF signal in a second frequency band) includes: in a first operating mode in which an input RF signal in the first frequency band is input, setting the second transistor and a fourth transistor to a cutoff state, where a third transistor amplifies an output RF signal of the first transistor; and in a second operating mode in which an input RF signal in the second frequency band is input, setting the first transistor and the third transistor to a cutoff state, where the fourth transistor amplifies an output RF signal of the second transistor.

[0017] In the first operating mode, setting the first transistor and the third transistor to a conducting state, and in the second operating mode, setting the second transistor and the fourth transistor to a conducting state.

[0018] In the first operating mode, a bias voltage of the second transistor is set to a cutoff voltage level, and a bias voltage of the fourth transistor can be set to a cutoff voltage level, and in the second operating mode, a bias voltage of the first transistor is set to a cutoff voltage level, and a bias voltage of the third transistor can be set to a cutoff voltage level.

[0019] In the first operating mode, a bias voltage of the first transistor can be set to a conducting voltage level, and a bias voltage of the third transistor is set to a conducting voltage level, and in the second operating mode, a bias voltage of the second transistor can be set to a conducting voltage level, and a bias voltage of the fourth transistor is set to a conducting voltage level.

[0020] In the first operating mode, an RF signal path can be formed through the first transistor and the third transistor, and in the second operating mode, an RF signal path can be formed through the second transistor and the fourth transistor.

[0021] In one general aspect, a low-noise amplifier includes: a first transistor configured to amplify an input radio frequency (RF) signal in a first frequency band; a second transistor configured to amplify an input RF signal in a second frequency band; a third transistor configured to amplify an output RF signal of the first transistor and configured to cutoff when the first transistor is cutoff; and a fourth transistor configured to amplify an output RF signal of the second transistor and configured to cutoff when the second transistor is cutoff.

[0022] In the first operating mode, an RF signal path can be formed through the first transistor and the third transistor, and in the second operating mode, an RF signal path can be formed through the second transistor and the fourth transistor.

[0023] Other features and aspects will be readily apparent from the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A general band selection switch and an example low noise amplifier (LNA) according to one or more embodiments are shown.

[0025] Figure 2 is a circuit diagram showing a low noise amplifier according to one or more embodiments.

[0026] Figure 3A The operation of an example low noise amplifier in the first operating mode and the radio frequency (RF) signal path are shown.

[0027] Figure 3B The operation of an example low noise amplifier in the second operating mode and the RF signal path are shown.

[0028] Figure 4 An example low noise amplifier according to one or more embodiments is shown.

[0029] Figure 5A The operation of the low noise amplifier in the first operating mode and the RF signal path are shown.

[0030] Figure 5B The operation of the low noise amplifier in the second operating mode and the RF signal path are shown.

[0031] Throughout the drawings and the detailed description, unless otherwise described, the same reference numerals refer to the same elements. The drawings may not be drawn to scale, and the relative dimensions, scales, and depictions of the elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0032] The following specific embodiments are provided to assist the reader in obtaining a comprehensive understanding of the methods, devices, and / or systems described herein. However, after understanding the disclosure of this application, various changes, modifications, and equivalents of the methods, devices, and / or systems described herein will be readily apparent. For example, the order of operations and / or the order within an operation described herein are merely examples and are not limited to the order set forth herein, but rather changes that will be readily apparent after understanding the disclosure of this application may be made, except for the order of operations and / or the order within an operation that must occur in a specific order. As another example, the order of operations and / or the order within an operation may be performed in parallel, except for at least a portion of the order of operations and / or the order within an operation that must occur in sequence (e.g., a specific order). Additionally, for increased clarity and brevity, descriptions of features known after understanding the disclosure of this application may be omitted.

[0033] Although terms such as "first", "second", and "third" or A, B, (a), (b), etc. may be used herein to describe various members, components, regions, layers, or parts, these members, components, regions, layers, or parts will not be limited by these terms. Each of these terms is not used to define, for example, the nature, order, or sequence of the corresponding member, component, region, layer, or part, but is only used to distinguish the corresponding member, component, region, layer, or part from other members, components, regions, layers, or parts. Thus, in the examples described herein, the first member, first component, first region, first layer, or first part referred to may also be referred to as the second member, second component, second region, second layer, or second part without departing from the teachings of the examples.

[0034] Throughout the specification, when a component, element, or layer is described as "on", "connected to", "coupled to", or "joined to" another component, element, or layer, it may be directly "on", "connected to", "coupled to", or "joined to" the other component, element, or layer (e.g., in contact with the other component, element, or layer), or there may reasonably be one or more other components, elements, or layers therebetween. When a component, element, or layer is described as "directly on", "directly connected to", "directly coupled to", or "directly joined to" another component, element, or layer, there are no other components, elements, or layers therebetween. Similarly, expressions such as "between" and "directly between" and "adjacent to" and "directly adjacent to" may also be interpreted as described above.

[0035] The terms used herein are for describing various examples only and are not intended to limit the disclosure. Unless the context clearly dictates otherwise, singular expressions (e.g., "a," "an," and "the") are also intended to include plural expressions. As a non-limiting example, the terms "comprising," "including," and "having" enumerate the presence of the stated features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof, or the alternative presence of the stated optional features, quantities, operations, components, elements, and / or combinations thereof. Additionally, while one embodiment may state that "comprising," "including," and "having" such terms enumerate the presence of the stated features, quantities, operations, components, elements, and / or combinations thereof, there may be other embodiments in which one or more of the stated features, quantities, operations, components, elements, and / or combinations thereof are absent.

[0036] As used herein, the term "and / or" includes any one of the related listed items or any combination of any two or more of them. Phrases such as "at least one of A, B, and C," "at least one of A, B, or C," etc. are intended to have a disjunctive meaning, and unless the corresponding description and examples require such listings (e.g., "at least one of A, B, and C") to be interpreted as having a conjunctive meaning, these phrases "at least one of A, B, and C," "at least one of A, B, or C," etc. also include examples where one or more of each of A, B, and / or C may be present (e.g., any combination of one or more of each of A, B, and C).

[0037] The features described herein may be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are provided only to illustrate some of the many possible ways of implementing the methods, devices, and / or systems described herein that will be readily understood after understanding the disclosure of the present application. The use of the term "may" herein with respect to an example or embodiment (e.g., with respect to what an example or embodiment may include or implement) means that there is at least one example or embodiment that includes or implements such a feature, and is not limited to all examples or embodiments including or implementing such a feature. The terms "example" and "embodiment" used herein have the same meaning (e.g., the phrase "in one example" has the same meaning as "in one embodiment," and "in one or more examples" has the same meaning as "in one or more embodiments").

[0038] In all one or more examples, by way of example only, RF signals may have, but are not limited to, formats according to the following protocols: Wi-Fi (such as IEEE 802.11 series), WiMAX (such as IEEE 802.16 series), IEEE 802.20, Long Term Evolution (LTE), Evolution-Data Optimized (Ev-DO), High Speed Packet Access Plus (HSPA+), High Speed Downlink Packet Access Plus (HSDPA+), High Speed Uplink Packet Access Plus (HSUPA+), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), Global Positioning System (GPS), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Digital Enhanced Cordless Telecommunications (DECT), Bluetooth, 3rd Generation Partnership Project (3G), 4th Generation Partnership Project (4G), 5th Generation Partnership Project (5G), and any other wireless and wired protocols specified after the above protocols.

[0039] Additionally, unless explicitly described to the contrary, the word "comprising" will be understood to imply including the stated elements but not excluding any other elements.

[0040] One or more examples may provide a low noise amplifier that reduces the noise figure and has multi-band operation.

[0041] According to one or more examples, isolation can be improved by separately forming RF signal paths for each band.

[0042] Figure 1 A general band selection switch 10 and a low noise amplifier (LNA) 20 are shown.

[0043] An input RF signal RF in a first band IN_B1 and an input RF signal RF in a second band IN_B2 can be input to the band selection switch 10. The input RF signal in the first band is an RF signal having the first band, and the input RF signal in the second band is an RF signal having the second band. In an example, the first band may be a different band from the second band.

[0044] The band selection switch 10 can select and output an input RF signal RF in the first band IN_B1 and an input RF signal RF in the second band IN_B2 That is, the band selection switch 10 can switch the input RF signal RF in the first band IN_B1 and the input RF signal RF in the second band IN_B2。In the example, the band selection switch 10 may be a single-pole N-throw (SPNT) switch, and as an example, it may be a single-pole double-throw (SPDT) switch.

[0045] The low-noise amplifier 20 can amplify the RF signal output from the band selection switch 10. When the input RF signal RF in the first band is output from the band selection switch 10 IN_B1 the low-noise amplifier 20 amplifies the input RF signal RF in the first band IN_B1 。When the input RF signal RF in the second band is output from the band selection switch 10 IN_B2 the low-noise amplifier 20 amplifies the input RF signal RF in the second band IN_B2 。That is, the low-noise amplifier 20 can have a multi-band operation of amplifying input RF signals with different bands.

[0046] In Figure 1 the structure shown, an insertion loss IL may be generated due to the band selection switch 10. This insertion loss may affect the overall noise figure. In Figure 1 the structure shown, the overall noise figure can be expressed as Equation 1 below.

[0047] Equation 1: In Equation 1, NF_total represents the overall noise figure, IL_BSS represents the insertion loss IL of the band selection switch 10, and NF_LNA represents the noise figure of the low-noise amplifier 20.

[0048] To reduce the insertion loss caused by the band selection switch 10, it may be necessary to remove the band selection switch 10. In an example according to the present disclosure, it would be advantageous for the low-noise amplifier 20 to perform the operation of the band selection switch internally, and the low-noise amplifier will be described below. That is, the low-noise amplifiers 200A or 200B described below can not only perform an amplification operation but also perform the operation of a band selection switch.

[0049] Figure 2 is a circuit diagram showing a low-noise amplifier 200A according to one or more embodiments.

[0050] As Figure 2 shown, the low-noise amplifier 200A according to one or more embodiments may include a first input matching network 210_1, a second input matching network 210_2, a first transistor M1_1, a second transistor M1_2, and a third transistor M2. The low-noise amplifier 200A may also include a first inductor L1_1, a second inductor L1_2, and a third inductor L2.

[0051] In Figure 2In [the circuit], transistors M1_1, M1_2, and M2 can be implemented as various transistors (such as, but not limited to, field effect transistors (FETs) and bipolar transistors). In Figure 2 [the circuit], transistors M1_1, M1_2, and M2 are shown as n-type transistors. However, this is merely an example, and transistors M1_1, M1_2, and M2 can be replaced with p-type transistors. Hereinafter, for ease of explanation, it is assumed that transistors M1_1, M1_2, and M2 are FETs, but they can also be replaced with other transistors.

[0052] In the example, the gates of transistors M1_1, M1_2, and M2 can operate as control terminals, and thus can be respectively identified as "control terminals". The drains of transistors M1_1, M1_2, and M2 are one terminal of the transistors, and thus can be respectively identified as "first terminal" or "second terminal". The sources of transistors M1_1, M1_2, and M2 are the other terminal of the transistors, and thus can be respectively identified as "second terminal" or "first terminal".

[0053] The input RF signal RF in the first frequency band IN_B1 can be input to the first input matching network 210_1, and the first input matching network 210_1 can be connected between the terminal of the input RF signal RF in the first frequency band IN_B1 and the gate of the first transistor M1_1. The first input matching network 210_1 can perform impedance matching between the input RF signal RF in the first frequency band IN_B1 and the first transistor M1_1. The first input matching network 210_1 can be implemented by a combination of at least one of an inductor and a capacitor.

[0054] The input RF signal RF in the second frequency band IN_B2 can be input to the second input matching network 210_2, and the second input matching network 210_2 can be connected between the terminal of the input RF signal RF in the second frequency band IN_B2 and the gate of the second transistor M1_2. The second input matching network 210_2 can perform impedance matching between the input RF signal RF in the second frequency band IN_B2 and the second transistor M1_2. The second input matching network 210_2 can be implemented by a combination of at least one of an inductor and a capacitor.

[0055] The first transistor M1_1 can be an amplifying transistor, and the input RF signal RF in the first frequency band IN_B1 can be input to the gate of the first transistor M1_1. The first transistor M1_1 amplifies the input RF signal RF in the first frequency band IN_B1。The bias voltage VB1_1 can be applied to the gate of the first transistor M1_1. The first transistor M1_1 can perform an amplification operation based on the bias voltage VB1_1. The amplified signal can be output from the drain of the first transistor M1_1. Since the input RF signal RF in the first frequency band to be amplified IN_B1 is input to the gate of the first transistor M1_1 and the amplified signal is output from the drain of the first transistor M1_1, the first transistor M1_1 can have a common-source amplification structure.

[0056] In the example, the bias voltage VB1_1 can have two voltage levels. That is, the bias voltage VB1_1 can have a conduction voltage level VB1_1_ON and a cut-off voltage level VB1_1_OFF. When the bias voltage VB1_1 is at the conduction voltage level VB1_1_ON, the first transistor M1_1 performs an amplification operation. When the bias voltage VB1_1 is at the cut-off voltage level VB1_1_OFF, the first transistor M1_1 does not perform an amplification operation. When the low-noise amplifier 200A amplifies the input RF signal RF in the first frequency band IN_B1 , the bias voltage VB1_1 can be set to the conduction voltage level VB1_1_ON. When the low-noise amplifier 200A amplifies the input RF signal RF in the second frequency band IN_B2 ,the bias voltage VB1_1 can be set to the cut-off voltage level VB1_1_OFF. As an example, the conduction voltage level VB1_1_ON can be 1.8V, and the cut-off voltage level VB1_1_OFF can be 0V.

[0057] The second transistor M1_2 can be an amplification transistor, and the input RF signal RF in the second frequency band IN_B2 can be input to the gate of the second transistor M1_2. The second transistor M1_2 amplifies the input RF signal RF in the second frequency band IN_B2 。The bias voltage VB1_2 can be applied to the gate of the second transistor M1_2. The second transistor M1_2 can perform an amplification operation based on the bias voltage VB1_2. The amplified signal can be output from the drain of the second transistor M1_2. Since the input RF signal RF in the second frequency band to be amplified IN_B2 is input to the gate of the second transistor M1_2 and the amplified signal is output from the drain of the second transistor M1_2, the second transistor M1_2 can have a common-source amplification structure.

[0058] In the example, the bias voltage VB1_2 can have two voltage levels. That is, the bias voltage VB1_2 can have a conduction voltage level VB1_2_ON and a cut-off voltage level VB1_2_OFF. When the bias voltage VB1_2 is at the conduction voltage level VB1_2_ON, the second transistor M1_2 performs an amplification operation. When the bias voltage VB1_2 is at the cut-off voltage level VB1_2_OFF, the second transistor M1_2 does not perform an amplification operation. When the low-noise amplifier 200A amplifies the input RF signal RF IN_B2 in the second frequency band, the bias voltage VB1_2 can be set to the conduction voltage level VB1_2_ON. When the low-noise amplifier 200A amplifies the input RF signal RFIN_B1 in the first frequency band, the bias voltage VB1_2 can be set to the cut-off voltage level VB1_2_OFF. As an example, the conduction voltage level VB1_2_ON can be 1.8V, and the cut-off voltage level VB1_2_OFF can be 0V.

[0059] The first inductor L1_1 can be connected between the source of the first transistor M1_1 and ground. The first inductor L1_1 can be a degeneration circuit and can improve the impedance matching of the first input matching network 210_1. Thus, the first inductor L1_1 can optimize the gain and noise figure of the first transistor M1_1. When the first transistor M1_1 is implemented as a bipolar transistor, the first inductor L1_1 can provide emitter degeneration. When the first transistor M1_1 is implemented as a field-effect transistor (FET), the first inductor L1_1 can provide source degeneration. In the example, the first inductor L1_1 can be replaced by a resistor to operate as a degeneration circuit.

[0060] The second inductor L1_2 can be connected between the source of the second transistor M1_2 and ground. The second inductor L1_2 can be a degeneration circuit and can improve the impedance matching of the second input matching network 210_2. Therefore, the second inductor L1_2 can optimize the gain and noise figure of the second transistor M1_2. When the second transistor M1_2 is implemented as a bipolar transistor, the second inductor L1_2 can provide emitter degeneration. When the second transistor M1_2 is implemented as a field-effect transistor (FET), the second inductor L1_2 can provide source degeneration. In the example, the second inductor L1_2 can be replaced by a resistor to operate as a degeneration circuit.

[0061] The third transistor M2 can form a cascode structure together with the first transistor M1_1 and can amplify the output signal of the first transistor M1_1. The third transistor M2 can form a cascode structure together with the second transistor M1_2 and can amplify the output signal of the second transistor M1_2. That is to say, the third transistor M2 can amplify both the output signal of the first transistor M1_1 and the output signal of the second transistor M1_2.

[0062] The source of the third transistor M2 can be connected to the drains of the first transistor M1_1 and the second transistor M1_2. The source of the third transistor M2 can receive the RF signal to be amplified from the first transistor M1_1, and the source of the third transistor M2 can receive the RF signal to be amplified from the second transistor M1_2. That is to say, the third transistor M2 can amplify the RF signal output from the drain of the first transistor M1_1, and the third transistor M2 can amplify the RF signal output from the drain of the second transistor M1_2. The drain of the third transistor M2 can output the amplified signal. That is to say, the drain of the third transistor M2 is the output terminal of the low-noise amplifier 200A and outputs the output RF signal RF OUT for output.

[0063] The bias voltage VB2 can be applied to the gate of the third transistor M2. The third transistor M2 can perform an amplification operation based on the bias voltage VB2. Since the third transistor M2 amplifies both the output signal of the first transistor M1_1 and the output signal of the second transistor M1_2, the bias voltage VB2 can always be set to the conduction voltage level VB2_ON.

[0064] The third inductor L2 can be connected between the power supply voltage VDD and the drain of the third transistor M2. The third transistor M2 can receive the power supply voltage VDD through the third inductor L2. In the example, the third inductor L2 can perform an RF choke operation or an output impedance matching operation.

[0065] Hereinafter, reference will be made to Figure 3A and Figure 3B to describe the operation and RF signal path of the low-noise amplifier 200A in the first operating mode and the second operating mode. In the example, the first operating mode can be the mode when an input RF signal RF in the first frequency band IN_B1 is input to the low-noise amplifier 200A. The second operating mode can be the mode when an input RF signal RF in the second frequency band IN_B2 is input to the low-noise amplifier 200A.

[0066] Figure 3A is a diagram showing the operation and RF signal path of the low-noise amplifier 200A in the first operating mode.

[0067] In a first operation mode, an input RF signal RF in a first frequency band is input IN_B1 . In this example, the bias voltage VB1_1 is set to the on voltage level VB1_1_ON, and the bias voltage VB1_2 is set to the off voltage level VB1_2_OFF. The bias voltage VB2 is set to the on voltage level VB2_ON. Accordingly, the first transistor M1_1 and the third transistor M2 perform an amplification operation, and the second transistor M1_2 does not perform an amplification operation.

[0068] In the first operation mode, an RF signal path RFP1 is formed through the first input matching network 210_1, the first transistor M1_1, and the third transistor M2.

[0069] Figure 3B FIG. is a diagram showing the operation of the low-noise amplifier 200A and the RF signal path in a second operation mode.

[0070] In a second operation mode, an input RF signal RF in a second frequency band is input IN_B2 . In this example, the bias voltage VB1_1 is set to the off voltage level VB1_1_OFF, and the bias voltage VB1_2 is set to the on voltage level VB1_2_ON. The bias voltage VB2 is set to the on voltage level VB2_ON. Accordingly, the second transistor M1_2 and the third transistor M2 perform an amplification operation, and the first transistor M1_1 does not perform an amplification operation.

[0071] In the second operation mode, an RF signal path RFP2 is formed through the second input matching network 210_2, the second transistor M1_2, and the third transistor M2.

[0072] In this way, the low-noise amplifier 200A according to one or more embodiments can selectively amplify the input RF signal in each frequency band by adjusting the level of the bias voltage. Accordingly, a separate band selection switch is not required at the front end of the low-noise amplifier 200A. Since insertion loss caused by the band selection switch does not occur, the overall noise figure can be reduced. That is, the low-noise amplifier 200A according to one or more embodiments can perform the operation of the band selection switch internally, thereby not only reducing the noise figure but also performing multi-band operation.

[0073] In the example, with reference to Figure 3A and Figure 3B, in the first operation mode and the second operation mode, the third transistor M2 performs an amplification operation. In this example, the RF signal path RFP1 and the RF signal path RFP2 can pass through the same transistor (i.e., the third transistor M2). As a result, since the input RF signal is input to a transistor that does not perform an amplification operation (e.g., the second transistor M1_2 in the first operation mode and the first transistor M1_1 in the second operation mode), the isolation may deteriorate. That is, since there is some overlap between the RF signal path RFP1 and the RF signal path RFP2, the isolation between the two RF signal paths may deteriorate. Hereinafter, embodiments that can improve the deterioration of isolation will be described.

[0074] Figure 4 FIG. is a diagram showing a low-noise amplifier 200B according to one or more embodiments.

[0075] As Figure 4 shown, the low-noise amplifier 200B according to one or more embodiments may include a first input matching network 210_1, a second input matching network 210_2, a first transistor M1_1, a second transistor M1_2, a third transistor M2_1, and a fourth transistor M2_2. The low-noise amplifier 200B may further include a first inductor L1_1, a second inductor L1_2, and a third inductor L3. Figure 4 The low-noise amplifier 200B of Figure 2 is similar to the low-noise amplifier 200A of

[0076] Refer to Figure 4 , the transistors M1_1, M1_2, M2_1, and M2_2 can be implemented as various transistors (such as but not limited to, field effect transistors (FETs) and bipolar transistors). In Figure 4 , the transistors M1_1, M1_2, M2_1, and M2_2 are shown as n-type transistors. However, this is merely an example, and the transistors M1_1, M1_2, M2_1, and M2_2 can be replaced with p-type transistors. Hereinafter, for the sake of convenience of explanation, it is assumed that the transistors M1_1, M1_2, M2_1, and M2_2 are FETs, but they can also be replaced with other transistors.

[0077] In the example, the gates of the transistors M1_1, M1_2, M2_1, and M2_2 can operate as control terminals, and thus can be respectively identified as "control terminals". The drains of the transistors M1_1, M1_2, M2_1, and M2_2 are one terminal of the transistors, and thus can be respectively identified as "first terminal" or "second terminal". The sources of the transistors M1_1, M1_2, M2_1, and M2_2 are the other terminal of the transistors, and thus can be respectively identified as "second terminal" or "first terminal".

[0078] The input RF signal RF in the first frequency band IN_B1 can be input to the first input matching network 210_1, and the first input matching network 210_1 can perform impedance matching between the input RF signal RF in the first frequency band IN_B1 and the first transistor M1_1.

[0079] The input RF signal RF in the second frequency band IN_B2 can be input to the second input matching network 210_2, and the second input matching network 210_2 can perform impedance matching between the input RF signal RF in the second frequency band IN_B2 and the second transistor M1_2.

[0080] The input RF signal RF in the first frequency band IN_B1 is input to the gate of the first transistor M1_1, and the first transistor M1_1 amplifies the input RF signal RF in the first frequency band IN_B1 . The bias voltage VB1_1 is applied to the gate of the first transistor M1_1, and the first transistor M1_1 can perform an amplification operation due to the bias voltage VB1_1. The amplified signal can be output from the drain of the first transistor M1_1.

[0081] The bias voltage VB1_1 can have a conduction voltage level VB1_1_ON and a cut-off voltage level VB1_1_OFF. When the bias voltage VB1_1 is at the conduction voltage level VB1_1_ON, the first transistor M1_1 performs an amplification operation. When the bias voltage VB1_1 is at the cut-off voltage level VB1_1_OFF, the first transistor M1_1 does not perform an amplification operation. When the low-noise amplifier 200B amplifies the input RF signal RF IN_B1 in the first frequency band, the bias voltage VB1_1 can be set to the conduction voltage level VB1_1_ON. When the low-noise amplifier 200B amplifies the input RF signal RF IN_B2 in the second frequency band, the bias voltage VB1_1 can be set to the cut-off voltage level VB1_1_OFF.

[0082] The input RF signal RF in the second frequency band IN_B2 is input to the gate of the second transistor M1_2, and the second transistor M1_2 amplifies the input RF signal RF in the second frequency band IN_B2 . The bias voltage VB1_2 is applied to the gate of the second transistor M1_2, and the second transistor M1_2 can perform an amplification operation based on the bias voltage VB1_2. The amplified signal can be output from the drain of the second transistor M1_2.

[0083] The bias voltage VB1_2 may have a conduction voltage level VB1_2_ON and a cut-off voltage level VB1_2_OFF. When the bias voltage VB1_2 is at the conduction voltage level VB1_2_ON, the second transistor M1_2 performs an amplification operation. When the bias voltage VB1_2 is at the cut-off voltage level VB1_2_OFF, the second transistor M1_2 does not perform an amplification operation. When the low-noise amplifier 200B amplifies the input RF signal RF in the second frequency band IN_B2 the bias voltage VB1_2 may be set to the conduction voltage level VB1_2_ON. When the low-noise amplifier 200B amplifies the input RF signal RF in the first frequency band IN_B1 the bias voltage VB1_2 may be set to the cut-off voltage level VB1_2_OFF.

[0084] The first inductor L1_1 may be connected between the source of the first transistor M1_1 and the ground, and the second inductor L1_2 may be connected between the source of the second transistor M1_2 and the ground. Since the inductors L1_1 and L1_2, which are degenerative inductors, are respectively connected to the first transistor M1_1 and the second transistor M1_2, the low-noise amplifier 200B can optimize the gain and noise figure according to the frequency band. That is, the first inductor L1_1 may be implemented to be optimal for the input RF signal RF in the first frequency band IN_B1 and the second inductor L1_2 may be implemented to be optimal for the input RF signal RF in the second frequency band IN_B2 is optimal.

[0085] The third transistor M2_1 may form a cascode structure together with the first transistor M1_1 and may amplify the output signal of the first transistor M1_1. The source of the third transistor M2_1 is connected to the drain of the first transistor M1_1, and the source of the third transistor M2_1 may receive the RF signal to be amplified from the first transistor M1_1. That is, the third transistor M2_1 may amplify the RF signal output from the drain of the first transistor M1_1. In addition, the drain of the third transistor M2_1 is connected to the drain of the fourth transistor M2_2, and the drain of the third transistor M2_1 may output the amplified signal. That is, the drain of the third transistor M2_1 is the output terminal of the low-noise amplifier 200B and outputs the output RF signal RF OUT for output.

[0086] A bias voltage VB2_1 can be applied to the gate of the third transistor M2_1. The third transistor M2_1 can perform an amplification operation based on the bias voltage VB2_1. In an example, the bias voltage VB2_1 can have two voltage levels. That is, the bias voltage VB2_1 can have a conduction voltage level VB2_1_ON and a cut-off voltage level VB2_1_OFF. When the bias voltage VB2_1 is at the conduction voltage level VB2_1_ON, the third transistor M2_1 performs an amplification operation. When the bias voltage VB2_1 is at the cut-off voltage level VB2_1_OFF, the third transistor M2_1 does not perform an amplification operation. When the low-noise amplifier 200B amplifies the input RF signal RF in the first frequency band IN_B1 the bias voltage VB2_1 can be set to the conduction voltage level VB2_1_ON. When the low-noise amplifier 200B amplifies the input RF signal RF in the second frequency band IN_B2 the bias voltage VB2_1 can be set to the cut-off voltage level VB2_1_OFF. In an example, the conduction voltage level VB2_1_ON can be 1.8V, and the cut-off voltage level VB2_1_OFF can be 0V.

[0087] The fourth transistor M2_2 can form a cascode structure together with the second transistor M1_2 and can amplify the output signal of the second transistor M1_2. The source of the fourth transistor M2_2 is connected to the drain of the second transistor M1_2, and the source of the fourth transistor M2_2 can receive the RF signal to be amplified from the second transistor M1_2. That is, the fourth transistor M2_2 can amplify the RF signal output from the drain of the second transistor M1_2. Additionally, the drain of the fourth transistor M2_2 is connected to the drain of the third transistor M2_1, and the drain of the fourth transistor M2_2 can output the amplified signal. That is, the drain of the fourth transistor M2_2 is the output terminal of the low-noise amplifier 200B and outputs the output RF signal RF OUT for output.

[0088] A bias voltage VB2_2 can be applied to the gate of the fourth transistor M2_2. The fourth transistor M2_2 can perform an amplification operation based on the bias voltage VB2_2.

[0089] In an example, the bias voltage VB2_2 can have two voltage levels. That is, the bias voltage VB2_2 can have a conduction voltage level VB2_2_ON and a cut-off voltage level VB2_2_OFF. When the bias voltage VB2_2 is at the conduction voltage level VB2_2_ON, the fourth transistor M2_2 performs an amplification operation. When the bias voltage VB2_2 is at the cut-off voltage level VB2_2_OFF, the fourth transistor M2_2 does not perform an amplification operation. When the low-noise amplifier 200B amplifies the input RF signal RF in the second frequency bandIN_B2 When, the bias voltage VB2_2 can be set to the turn-on voltage level VB2_2_ON. When the low-noise amplifier 200B amplifies the input RF signal RF in the first frequency band IN_B1 When, the bias voltage VB2_2 can be set to the turn-off voltage level VB2_2_OFF. In the example, the turn-on voltage level VB2_2_ON can be 1.8V, and the turn-off voltage level VB2_2_OFF can be 0V.

[0090] The first end of the third inductor L3 can be connected to the power supply voltage VDD, and the second end of the third inductor L3 can be connected to the drain of the third transistor M2_1 and the drain of the fourth transistor M2_2. The third transistor M2_1 and the fourth transistor M2_2 can receive the power supply voltage VDD through the third inductor L3. In the example, the third inductor L3 can perform an RF choke operation or an output impedance matching operation.

[0091] In the example, the third inductor L3 can be a variable inductor. When the third inductor L3 is a variable inductor, the inductance value of the third inductor L3 can vary according to the frequency band of the input RF signal. When the input RF signal RF in the first frequency band IN_B1 When, the inductance value of the third inductor L3 can be set to be optimal for the input RF signal RF in the first frequency band IN_B1 When the input RF signal RF in the second frequency band IN_B2 When, the inductance value of the third inductor L3 can be set to be optimal for the input RF signal RF in the second frequency band IN_B2 That is, the inductance value of the third inductor L3 can vary according to the operation modes (the first operation mode and the second operation mode).

[0092] Hereinafter, reference will be made to Figure 5A and Figure 5B to describe the operation and RF signal path of the low-noise amplifier 200B in the first operation mode and the second operation mode. In the example, the first operation mode can be the mode when the input RF signal RF in the first frequency band IN_B1 is input to the low-noise amplifier 200B. The second operation mode can be the mode when the input RF signal RF in the second frequency band IN_B2 is input to the low-noise amplifier 200B.

[0093] Figure 5A shows the operation and RF signal path of the low-noise amplifier 200B in the first operation mode.

[0094] Referring to Figure 5A In the first operation mode, the input RF signal RF in the first frequency band is input IN_B1。In this example, the bias voltage VB1_1 is set to the turn-on voltage level VB1_1_ON, and the bias voltage VB2_1 is set to the turn-on voltage level VB2_1_ON. The bias voltage VB1_2 is set to the turn-off voltage level VB1_2_OFF, and the bias voltage VB2_2 is set to the turn-off voltage level VB2_2_OFF. Therefore, the first transistor M1_1 and the third transistor M2_1 perform an amplification operation, and the second transistor M1_2 and the fourth transistor M2_2 do not perform an amplification operation.

[0095] In the first operation mode, an RF signal path RFP3 is formed through the first input matching network 210_1, the first transistor M1_1, and the third transistor M2_1.

[0096] Figure 5B The operation of the low-noise amplifier 200B and the RF signal path in the second operation mode are shown.

[0097] Referring to Figure 5B , in the second operation mode, an input RF signal RF in the second frequency band is input. IN_B2 。In this example, the bias voltage VB1_2 is set to the turn-on voltage level VB1_2_ON, and the bias voltage VB2_2 is set to the turn-on voltage level VB2_2_ON. The bias voltage VB1_1 is set to the turn-off voltage level VB1_1_OFF, and the bias voltage VB2_1 is set to the turn-off voltage level VB2_1_OFF. Therefore, the second transistor M1_2 and the fourth transistor M2_2 perform an amplification operation, and the first transistor M1_1 and the third transistor M2_1 do not perform an amplification operation.

[0098] In the second operation mode, an RF signal path RFP4 is formed through the second input matching network 210_2, the second transistor M1_2, and the fourth transistor M2_2.

[0099] In this way, the low-noise amplifier 200B according to one or more embodiments can selectively amplify the input RF signal in each frequency band by adjusting the level of the bias voltage. Therefore, a separate band selection switch is not required at the front end of the low-noise amplifier 200B. Since the insertion loss caused by the band selection switch does not occur, the overall noise figure can be reduced. That is, the low-noise amplifier 200B according to one or more embodiments performs the operation of the band selection switch internally, thereby not only reducing the noise figure but also performing multi-band operation.

[0100] Referring to Figure 5A and Figure 5B, in a low-noise amplifier 200B according to one or more embodiments, the RF signal path RFP3 in the first operating mode and the RF signal path RFP4 in the second operating mode are formed not to pass through the same transistor. Therefore, the isolation between the two RF signal paths can be improved. That is to say, the RF signal path RFP3 in the first operating mode and the RF signal path RFP4 in the second operating mode can be independent of each other, so the isolation between the two RF signal paths can be improved.

[0101] Although the present disclosure includes specific examples, it will be readily understood after understanding the disclosure of the present application that various changes in form and detail can be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be understood only in a descriptive sense and not for purposes of limitation. The description of a feature or aspect in each example is considered applicable to similar features or aspects in other examples. Appropriate results can be obtained if the described techniques are performed in a different order and / or if the components in the described systems, architectures, devices, or circuits are combined in a different manner and / or replaced or supplemented by other components or their equivalents.

[0102] Therefore, the scope of the present disclosure is not limited by the specific embodiments, but is defined by the claims and their equivalents, and all variations within the scope of the claims and their equivalents will be construed as being included in the present disclosure.

Claims

1. A low noise amplifier, comprising: a first transistor configured to amplify an input RF signal in a first frequency band and configured to receive a first bias voltage; a second transistor configured to amplify an input RF signal in a second frequency band and configured to receive a second bias voltage; a third transistor configured to amplify the output RF signal of the first transistor and configured to receive a third bias voltage; as well as a fourth transistor configured to amplify the output RF signal of the second transistor and configured to receive a fourth bias voltage, wherein, in the first operation mode, the second bias voltage and the fourth bias voltage are set to a cut-off voltage level, and Wherein, in the second operation mode, the first bias voltage and the third bias voltage are set to a cut-off voltage level.

2. The low noise amplifier according to claim 1, wherein: In the first operation mode, the first bias voltage and the third bias voltage are set to a turn-on voltage level, and In the second operation mode, the second bias voltage and the fourth bias voltage are set to a turn-on voltage level.

3. The low noise amplifier according to claim 2, wherein: In the first operation mode, the first transistor and the third transistor are configured to perform an amplification operation, and the second transistor and the fourth transistor do not perform an amplification operation, and In the second operation mode, the second transistor and the fourth transistor are configured to perform an amplification operation, and the first transistor and the third transistor do not perform an amplification operation.

4. The low noise amplifier according to claim 1, wherein: When an input radio frequency signal in the first frequency band is input, the first operation mode is performed, and When an input radio frequency signal in the second frequency band is input, the second operation mode is performed.

5. The low noise amplifier according to claim 1, wherein: The input radio frequency signal in the first frequency band and the first bias voltage are applied to the control terminal of the first transistor, and An input radio frequency signal in the second frequency band and the second bias voltage are applied to a control terminal of the second transistor.

6. The low noise amplifier according to claim 5, wherein: The third bias voltage is applied to the control terminal of the third transistor, and the output RF signal of the first transistor is applied to the first terminal of the third transistor, and The fourth bias voltage is applied to a control terminal of the fourth transistor, and the output RF signal of the second transistor is applied to a first terminal of the fourth transistor.

7. The low noise amplifier according to claim 6, further comprising: a first inductor connected between the first terminal of the first transistor and ground; as well as A second inductor is connected between the first terminal of the second transistor and the ground.

8. The low noise amplifier according to claim 6, further comprising: A third inductor includes a first end connected to the power supply voltage and a second end connected to the second terminal of the third transistor and the second terminal of the fourth transistor.

9. The low noise amplifier according to claim 8, wherein: An inductance value of the third inductor varies according to the first operation mode and the second operation mode.

10. A method of operating a low noise amplifier, the low noise amplifier comprising a first transistor that amplifies an input radio frequency signal in a first frequency band and a second transistor that amplifies an input radio frequency signal in a second frequency band, the method comprising: In a first operation mode in which an input RF signal in the first frequency band is input, setting the second transistor and the fourth transistor to a cut-off state, wherein the third transistor amplifies an output RF signal of the first transistor; and In a second operation mode in which an input radio frequency signal in the second frequency band is input, the first transistor and the third transistor are set to a cut-off state, wherein the fourth transistor amplifies an output radio frequency signal of the second transistor.

11. The method according to claim 10, further comprising: In the first operation mode, setting the first transistor and the third transistor to an on state; as well as In the second operation mode, the second transistor and the fourth transistor are set to an on state.

12. The method according to claim 11, wherein: In the first operation mode, the bias voltage of the second transistor is set to a cut-off voltage level, and the bias voltage of the fourth transistor is set to a cut-off voltage level, and In the second operation mode, the bias voltage of the first transistor is set to a cut-off voltage level, and the bias voltage of the third transistor is set to a cut-off voltage level.

13. The method according to claim 12, wherein: In the first operation mode, the bias voltage of the first transistor is set to a turn-on voltage level, and the bias voltage of the third transistor is set to a turn-on voltage level, and In the second operation mode, a bias voltage of the second transistor is set to a turn-on voltage level, and a bias voltage of the fourth transistor is set to a turn-on voltage level.

14. The method according to claim 13, wherein: In the first operation mode, a radio frequency signal path is formed by the first transistor and the third transistor, and In the second operation mode, a radio frequency signal path is formed through the second transistor and the fourth transistor.

15. A low noise amplifier, comprising: a first transistor configured to amplify an input RF signal in a first frequency band; a second transistor configured to amplify an input RF signal in a second frequency band; a third transistor configured to amplify the output RF signal of the first transistor and configured to be turned off when the first transistor is turned off; as well as The fourth transistor is configured to amplify the output RF signal of the second transistor and is configured to be turned off when the second transistor is turned off.

16. The low noise amplifier according to claim 15, wherein: In a first operation mode, a radio frequency signal path is formed by the first transistor and the third transistor, and In a second operation mode, a radio frequency signal path is formed by the second transistor and the fourth transistor.

Images