Differential amplifier circuit

Abstract

Provided is a differential amplifier circuit capable of further widening a frequency band reduced by a filter. A differential amplifier circuit (100A) includes a differential amplifier that outputs a signal containing a higher harmonic, a first filter that reduces the level of an even harmonic contained in the output of the differential amplifier, and a second filter. The first filter and the second filter are connected to the output of the differential amplifier. The first filter includes a resonance circuit based on a capacitor (108) and an inductor (114) and a resonance circuit based on a capacitor (110) and an inductor (114). The second filter includes a resonance circuit based on a capacitor (118) and an inductor (124) and a resonance circuit based on a capacitor (120) and an inductor (124). The center frequency of the first filter is lower than the center frequency of the even harmonic, and the center frequency of the second filter is higher than the center frequency of the even harmonic.

Description

Technical Field

[0001] This invention relates to differential amplifier circuits. Background Technology

[0002] Sometimes, filters are incorporated into differential amplifier circuits to reduce higher harmonics. For example, the differential amplifier circuit disclosed in Patent Document 1 includes a filter at the output of the differential amplifier for reducing higher harmonics. The signal with reduced higher harmonics by the filter is then output via an impedance matching circuit.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: U.S. Patent Application Publication No. 2017 / 0149394

[0006] However, the differential amplifier circuit disclosed in Patent Document 1 still has room for improvement in the frequency characteristics of the filter. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] This disclosure was made in view of the above circumstances, and its purpose is to provide a differential amplifier circuit that can further widen the bandwidth reduced by the filter.

[0009] Methods for solving problems

[0010] A differential amplifier circuit based on a certain aspect of this disclosure includes a differential amplifier that outputs a signal containing higher harmonics and a first filter and a second filter that reduce the level of even harmonics contained in the output of the differential amplifier. The first filter and the second filter are connected to the output of the differential amplifier. The center frequency of the first filter is lower than the center frequency of the even harmonics, and the center frequency of the second filter is higher than the center frequency of the even harmonics.

[0011] Invention Effects

[0012] According to the present invention, in a differential amplifier circuit, the bandwidth reduced by the filter can be further widened. Attached Figure Description

[0013] Figure 1 This is a diagram illustrating a first embodiment of the differential amplifier circuit of this disclosure.

[0014] Figure 2 This is a diagram showing a portion of a differential amplifier circuit.

[0015] Figure 3 This shows the differential mode. Figure 2 A diagram showing the state of the circuit.

[0016] Figure 4 This shows the in-phase mode. Figure 2 A diagram showing the state of the circuit.

[0017] Figure 5 This is a diagram showing a differential amplifier circuit in differential mode.

[0018] Figure 6 This is a graph showing the frequency characteristics of a differential amplifier circuit in differential mode.

[0019] Figure 7 This is a diagram showing a differential amplifier circuit in non-inverting mode.

[0020] Figure 8 This is a diagram showing the frequency characteristics of a differential amplifier circuit in in-phase mode.

[0021] Figure 9 This is a diagram illustrating a second embodiment of the differential amplifier circuit of this disclosure.

[0022] Figure 10 This is a diagram showing a differential amplifier circuit in differential mode.

[0023] Figure 11 This is a graph showing the frequency characteristics in differential mode based on a differential amplifier circuit.

[0024] Figure 12 This is a diagram showing a differential amplifier circuit in non-inverting mode.

[0025] Figure 13 This is a graph showing the frequency characteristics in non-inverting mode based on a differential amplifier circuit.

[0026] Figure 14 This is a diagram illustrating a third embodiment of the differential amplifier circuit of this disclosure.

[0027] Figure 15 This is a diagram showing a differential amplifier circuit in differential mode.

[0028] Figure 16 It is shown Figure 14 The frequency response of the differential amplifier circuit in differential mode is shown in the figure.

[0029] Figure 17 This is a diagram showing a differential amplifier circuit in non-inverting mode.

[0030] Figure 18 It is shown Figure 14 The frequency response of the differential amplifier circuit in non-inverting mode is shown in the figure.

[0031] Figure 19 This is a diagram illustrating a fourth embodiment of the differential amplifier circuit of this disclosure.

[0032] Figure 20 This is a diagram showing a differential amplifier circuit in differential mode.

[0033] Figure 21 It is shown Figure 19 The frequency response of the differential amplifier circuit in differential mode is shown in the figure.

[0034] Figure 22 This is a diagram showing a differential amplifier circuit in non-inverting mode.

[0035] Figure 23 It is shown Figure 19 The frequency response of the differential amplifier circuit in non-inverting mode is shown in the figure.

[0036] Figure 24 This is a diagram illustrating a fifth embodiment of the differential amplifier circuit of this disclosure.

[0037] Explanation of reference numerals in the attached figures

[0038] 100A, 100B, 100C, 100D: Differential amplifier circuit;

[0039] 103: Output terminal;

[0040] 104, 105: Amplifiers;

[0041] 106, 112, 114, 116, 122, 124, 132, 134: Inductors;

[0042] 108, 110, 118, 120, 140: Capacitors;

[0043] 130, 130a: Balanced / unbalanced converters. Detailed Implementation

[0044] Hereinafter, embodiments of the differential amplifier circuit of this disclosure will be described in detail based on the accompanying drawings. However, the present invention is not limited to these embodiments. Furthermore, the constituent elements of each embodiment include those that can be easily substituted by those skilled in the art or are substantially the same. Each embodiment is illustrative, and substitutions or combinations of parts of the structure shown in different embodiments are possible. Following the second embodiment, descriptions of matters common to the first embodiment are appropriately omitted, and the description focuses on the differences. In particular, descriptions of the same effects resulting from the same structure are appropriately omitted and are not mentioned repeatedly in each embodiment.

[0045] (First Embodiment)

[0046] [Circuit Structure]

[0047] Figure 1 This is a diagram illustrating a first embodiment of the differential amplifier circuit of this disclosure. The differential amplifier circuit 100A of the first embodiment is, for example, a differential amplifier circuit in a subsequent stage (power stage) located at the output of a primary (driver stage) amplifier circuit (not shown). Figure 1 As shown, the differential amplifier circuit 100A has amplifiers 104 and 105, capacitors 108, 110, 118 and 120, inductors 114 and 124 and a balun 130.

[0048] The first terminal of capacitor 108 and the first terminal of capacitor 118 are connected between amplifier 104 and balun 130. The first terminal of capacitor 110 and the first terminal of capacitor 120 are connected between amplifier 105 and balun 130.

[0049] The second terminals of capacitor 108 and capacitor 110 are connected. This connection point is designated as node N1. The first terminal of inductor 114 is connected to node N1. The second terminal of inductor 114 is connected to a reference potential. This reference potential is, for example, ground, but this disclosure is not limited thereto. The same applies in the following description.

[0050] Terminals 2 of capacitor 118 and 120 are connected. This connection point is designated as node N2. Terminal 1 of inductor 124 is connected to node N2. Terminal 2 of inductor 124 is connected to a reference potential.

[0051] The balun 130 includes an inductor 132 as the primary winding and an inductor 134 as the secondary winding. Inductor 132 and inductor 134 are magnetically coupled. The output of amplifier 104 is applied to the first terminal of inductor 132. The output of amplifier 105 is applied to the second terminal of inductor 132. The first terminal of inductor 134 is connected to the output terminal 103. The second terminal of inductor 134 is connected to a reference potential.

[0052] The differential amplifier circuit 100A, for example, is incorporated into mobile communication devices such as portable telephones, amplifying the power of the input signal to the level required for transmission to a base station and outputting it as the output signal. The input signal is, for example, a radio frequency (RF) signal modulated by an RFIC (Radio Frequency Integrated Circuit) or similar circuit according to a given communication method. The communication standard of the input signal includes, for example, 2G (2nd generation mobile communication system), 3G (3rd generation mobile communication system), 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), LTE (Long Term Evolution)-FDD (Frequency Division Duplex), LTE-TDD (Time Division Duplex), LTE-Advanced, or LTE-Advanced Pro, with frequencies ranging from hundreds of MHz to tens of GHz. However, the communication standard and frequency of the input signal are not limited to these.

[0053] When high-order harmonic signals are output from amplifiers 104 and 105, the operation of the differential amplifier circuit 100A can be considered in differential mode and common mode. Common mode focuses on the operation of even-order harmonics within the high-order harmonics. Differential mode focuses on the operation of odd-order harmonics within the high-order harmonics.

[0054] Here, focusing on Figure 1 It contains two capacitors, 108 and 110, and an inductor, 114. Figure 2 This is a diagram showing a portion of the differential amplifier circuit 100A. Figure 2 Two capacitors, 108 and 110, and an inductor, 114, are shown. Figure 2 In the diagram, node A is connected to the first terminal of capacitor 108. Furthermore, node A is connected to... Figure 1 The output connection of amplifier 104 is shown. Node A' is connected to the first terminal of capacitor 110. Furthermore, node A' is connected to... Figure 1 The output connection of amplifier 105 is shown. Node N1 is the midpoint between node A and node A'.

[0055] Figure 3 This shows the differential mode. Figure 2The diagram shows the state of the circuit. In differential mode, node N1, which is the midpoint, becomes a virtual short circuit relative to the reference potential. Therefore, in differential mode, if viewed from node A, i.e., amplifier 104, it appears that the reference potential is connected to the end of capacitor 108. Furthermore, in differential mode, if viewed from node A', i.e., amplifier 105, it appears that the reference potential is connected to the end of capacitor 110. In differential mode, the impedance of the fundamental frequency can be adjusted via capacitor 110.

[0056] Figure 4 This shows the in-phase mode. Figure 2 The diagram shows the state of the circuit. In non-inverting mode, node N1 does not form a virtual short circuit relative to the reference potential. Therefore, in non-inverting mode, viewed from node A (amplifier 104), it appears that the reference potential is connected to the end of the series circuit of capacitor 108 and inductor 114. Furthermore, in non-inverting mode, viewed from node A' (amplifier 105), it appears that the reference potential is connected to the end of the series circuit of capacitor 110 and inductor 114. Additionally, Figure 4 The inductance value of inductor 114 in the middle is Figure 2 The inductance of inductor 114 is twice that of the inductor in the middle.

[0057] In addition, for Figure 1 The two capacitors 118 and 120 and the inductor 124 in the differential mode also appear to be the same as Figure 3 Similarly, it also looks the same in in-phase mode. Figure 4 same.

[0058] (Differential mode)

[0059] Figure 5 This is a diagram showing the differential amplifier circuit 100A in differential mode. (See diagram for example.) Figure 5 As shown, in differential mode, it appears that the first terminal of capacitor 108 is connected to the output of amplifier 104, and the second terminal of capacitor 108 is connected to the reference potential. Furthermore, in differential mode, it appears that the first terminal of capacitor 118 is connected to the output of amplifier 104, and the second terminal of capacitor 118 is connected to the reference potential.

[0060] Furthermore, in differential mode, it appears that the first terminal of capacitor 110 is connected to the output of amplifier 105, and the second terminal of capacitor 110 is connected to the reference potential. Also, in differential mode, it appears that the first terminal of capacitor 120 is connected to the output of amplifier 105, and the second terminal of capacitor 120 is connected to the reference potential. Additionally, let capacitor 108 be capacitance value C1, capacitor 118 be capacitance value C2, capacitor 110 be capacitance value C3, and capacitor 120 be capacitance value C4.

[0061] Figure 6This is a graph showing the frequency characteristics of a 100A differential amplifier circuit in differential mode. Figure 6 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. For example... Figure 6 As shown, f0 is the fundamental frequency, 2f0 is the second harmonic frequency, 3f0 is the third harmonic frequency, and so on. The higher the order of the harmonic, the more it is attenuated by the horizontal.

[0062] (In-phase mode)

[0063] Figure 7 This is a diagram showing a differential amplifier circuit 100A in non-inverting mode. (See diagram for example.) Figure 7 As shown, in non-inverting mode, it appears that the first terminal of capacitor 108 is connected to the output of amplifier 104, the second terminal of capacitor 108 is connected to the first terminal of inductor 114, and the second terminal of inductor 114 is connected to a reference potential. Furthermore, in non-inverting mode, it appears that the first terminal of capacitor 118 is connected to the output of amplifier 104, the second terminal of capacitor 118 is connected to the first terminal of inductor 124, and the second terminal of inductor 124 is connected to a reference potential.

[0064] Furthermore, in non-inverting mode, it appears that the first terminal of capacitor 110 is connected to the output of amplifier 105, the second terminal of capacitor 110 is connected to the first terminal of inductor 114, and the second terminal of inductor 114 is connected to a reference potential. Also, in non-inverting mode, it appears that the first terminal of capacitor 120 is connected to the output of amplifier 105, the second terminal of capacitor 120 is connected to the first terminal of inductor 124, and the second terminal of inductor 124 is connected to a reference potential.

[0065] In non-inverting mode, capacitor 108 and inductor 114 operate as a resonant circuit. The resonant circuit based on capacitor 108 and inductor 114 becomes a first filter that attenuates the output of amplifier 104. The resonant frequency of this first filter is set as frequency fA. Frequency fA is a frequency slightly lower than the second harmonic frequency 2f0. If the capacitance value of capacitor 108 is set to C1 and the inductance value of inductor 114 is set to L2, then frequency fA can be expressed by equation (1).

[0066] fA=1 / 2π(C1×2L2)1 / 2……(1)

[0067] Since node N1 is the midpoint, the capacitance value C3 of capacitor 110 is equal to the capacitance value C1 of capacitor 108. Therefore, the resonant frequency of the resonant circuit based on capacitor 110 and inductor 114 is frequency fA. The term "equality" in this paper means that even differences caused by manufacturing errors are defined as equal.

[0068] Furthermore, in in-phase mode, capacitor 118 and inductor 124 operate as a resonant circuit. The resonant circuit based on capacitor 118 and inductor 124 becomes a second filter that attenuates the output of amplifier 104. The resonant frequency of this second filter is set as frequency fB. Frequency fB is a frequency slightly higher than the 2nd harmonic frequency 2f0. If the capacitance value of capacitor 118 is set to C2 and the inductance value of inductor 124 is set to L3, then frequency fB can be expressed by equation (2).

[0069] fB=1 / 2π(C2×2L3)1 / 2……(2)

[0070] Since node N2 is the midpoint, the capacitance C4 of capacitor 120 is equal to the capacitance C2 of capacitor 118. Therefore, the resonant frequency of the resonant circuit based on capacitor 120 and inductor 124 is frequency fB.

[0071] Figure 8 This is a graph showing the frequency characteristics of a 100A differential amplifier circuit in non-inverting mode. Figure 8 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. For example... Figure 8 As shown, frequency fA is a frequency slightly lower than the second harmonic frequency 2f0. That is, the resonant circuit based on capacitor 108 and inductor 114, and the resonant circuit based on capacitor 110 and inductor 114 operate as the first filter whose horizontal level drops the most at frequency fA. Furthermore, frequency fB is a frequency slightly higher than the second harmonic frequency 2f0. That is, the resonant circuit based on capacitor 118 and inductor 124, and the resonant circuit based on capacitor 120 and inductor 124 operate as the second filter whose horizontal level drops the most at frequency fB. Alternatively, the structure for implementing the resonant circuit at frequency fB can also be capacitor 110 and inductor 114. The structure for implementing the resonant circuit at frequency fA can also be capacitor 120 and inductor 124.

[0072] For reference Figure 8 As explained, frequency fA is slightly lower than the second harmonic frequency 2f0, and frequency fB is slightly higher than the second harmonic frequency 2f0. Frequency fA and frequency fB are slightly different. That is, the resonant frequencies of the first and second resonant circuits, which constitute the first and second filters, are slightly different.

[0073] When the fundamental frequency f0 of the signal output from amplifiers 104 and 105 is above f0_1 and below f0_2, the frequency of the 2-fold wave, i.e., the intermediate frequency fcenter1 between frequency fA and frequency fB, can be represented by equation (3).

[0074] fcenter1=(f0_1+f0_2) / 2×2……(3)

[0075] Moreover, the frequencies fA and fB can be represented by equations (4) and (5), for example.

[0076] fA≥fcenter1×0.9……(4)

[0077] fB≤fcenter1×1.1……(5)

[0078] That is, the center frequency of the first filter (e.g., frequency fA) is 0.9 times the center frequency of the even harmonic (e.g., frequency fcenter1), and the center frequency of the second filter (e.g., frequency fB) is 1.1 times the center frequency of the even harmonic (e.g., frequency fcenter1).

[0079] Thus, by using a first resonant circuit with slightly different resonant frequencies and a second filter, the frequency bands that decrease in horizontal direction can be made to overlap. By making the two frequency bands of these resonant circuits overlap, thus achieving... Figure 8 As shown, it is possible to reduce the pass-through level for frequencies below and above the twice-wavelength frequency 2f0 as the center frequency.

[0080] Furthermore, by coinciding the frequency bands of resonant circuits with higher Q values, the frequency band that causes the passivity to decrease can be widened. To obtain a wider frequency band, it might be possible to use only one resonant circuit with a lower Q value. However, the decrease in the passivity of a resonant circuit with a lower Q value is insufficient, and it cannot function as a filter. Therefore, in this disclosure, by using a first resonant circuit with a higher Q value and a second resonant circuit, and by coinciding the frequency bands that cause the passivity to decrease, a sufficient decrease in the passivity is achieved over a relatively wide frequency band.

[0081] Here, the relationship between the capacitance values ​​C1 of capacitor 108, C2 of capacitor 118, C3 of capacitor 110, and C4 of capacitor 120 is, for example, C1, C3 > C2, C4. If capacitance values ​​C1 and C2 are equal, both being relatively small values, then an additional capacitor is needed to achieve impedance matching for the fundamental frequency f0. For example, an additional capacitor needs to be added between the output of amplifier 104 and the output of amplifier 105. Conversely, if capacitance value C1 > capacitance value C2, then the desired frequency characteristics can be obtained without adding an additional capacitor. The same applies to capacitance values ​​C3 and C4.

[0082] Furthermore, when C1 and C3 are greater than C2 and C4, the relationship between the inductance value L2 of inductor 114 and the inductance value L3 of inductor 124 is, for example, L2 < L3.

[0083] [Effect]

[0084] As described above, by using a first resonant circuit with a slightly different resonant frequency and a first filter and a second filter, it is possible to make the frequency bands passing through the horizontal drop overlap. Therefore, the frequency band passing through the horizontal drop can be wider than that based on a single resonant circuit.

[0085] (Second Implementation)

[0086] [Circuit Structure]

[0087] Figure 9 This diagram illustrates a second embodiment of the differential amplifier circuit of this disclosure. The differential amplifier circuit 100B of the second embodiment is based on the differential amplifier circuit 100A of the first embodiment, with the addition of inductors 106, 112, 116, and 122. The first terminal of inductor 106 is connected to the output of amplifier 104, and its second terminal is connected to the first terminal of capacitor 108. The first terminal of inductor 116 is connected to the output of amplifier 104, and its second terminal is connected to the first terminal of capacitor 118. The first terminal of inductor 112 is connected to the output of amplifier 105, and its second terminal is connected to the first terminal of capacitor 110. The first terminal of inductor 122 is connected to the output of amplifier 105, and its second terminal is connected to the first terminal of capacitor 120.

[0088] (Differential mode)

[0089] Figure 10 This is a diagram showing the differential amplifier circuit 100B in differential mode. (See diagram for example.) Figure 10 As shown, in differential mode, a series resonant circuit based on inductor 106 and capacitor 108 appears to be connected between the output of amplifier 104 and node N1. Furthermore, it appears that the first terminal of inductor 106 is connected to the output of amplifier 104, and the first terminal of capacitor 108 is connected to a reference potential. Also in differential mode, a series resonant circuit based on inductor 116 and capacitor 118 appears to be connected between the output of amplifier 104 and node N2. Furthermore, it appears that the first terminal of inductor 116 is connected to the output of amplifier 104, and the first terminal of capacitor 118 is connected to a reference potential.

[0090] In addition, such as Figure 10As shown, in differential mode, a series resonant circuit based on inductor 112 and capacitor 110 appears to be connected between the output of amplifier 105 and node N1. Furthermore, it appears that the first terminal of inductor 112 is connected to the output of amplifier 105, and the first terminal of capacitor 110 is connected to a reference potential. Also in differential mode, a series resonant circuit based on inductor 122 and capacitor 120 appears to be connected between the output of amplifier 105 and node N2. Furthermore, it appears that the first terminal of inductor 122 is connected to the output of amplifier 105, and the first terminal of capacitor 120 is connected to a reference potential.

[0091] In differential mode, inductor 106 and capacitor 108 operate as a series resonant circuit. The resonant frequency of the resonant circuit based on inductor 106 and capacitor 108 is set as frequency fC. Frequency fC is a frequency slightly lower than the third harmonic frequency 3f0. If the capacitance of capacitor 108 is set to C1 and the inductance of inductor 106 is set to L5, then frequency fC can be expressed by equation (6).

[0092] fC=1 / 2π(C1×L5)1 / 2……(6)

[0093] Node N1 is the midpoint, therefore the capacitance C3 of capacitor 110 is equal to the capacitance C1 of capacitor 108, and the inductance L7 of inductor 112 is equal to the inductance L5 of inductor 106. Therefore, the resonant frequency of the resonant circuit based on inductor 112 and capacitor 110 is frequency fC. Furthermore, in this specification, "equal capacitance values" means that the capacitance values ​​are the same within the range of manufacturing tolerances. The same applies to inductance values; both mean that the inductance values ​​are the same within the range of manufacturing tolerances. The same principle applies to the following explanations.

[0094] Furthermore, in differential mode, inductor 116 and capacitor 118 operate as a series resonant circuit. The resonant frequency of the resonant circuit based on inductor 116 and capacitor 118 is set as frequency fD. Frequency fD is a frequency slightly higher than the third harmonic frequency 3f0. If the capacitance of capacitor 118 is set to C2 and the inductance of inductor 116 is set to L6, then frequency fD can be expressed by equation (7).

[0095] fD=1 / 2π(C1×L6)1 / 2……(7)

[0096] Since node N2 is the midpoint, the capacitance C4 of capacitor 120 is equal to the capacitance C2 of capacitor 118, and the inductance L8 of inductor 122 is equal to the inductance L6 of inductor 116. Therefore, the resonant frequency of the series resonant circuit of inductor 122 and capacitor 120 is frequency fD.

[0097] Figure 11This is a graph showing the frequency characteristics in differential mode based on the differential amplifier circuit 100B. Figure 11 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. For example... Figure 11 As shown, frequency fC is slightly lower than the third harmonic frequency 3f0. That is, the resonant circuit based on inductor 106 and capacitor 108 and the resonant circuit based on inductor 112 and capacitor 110 operate as filters where the pass level drops the most at frequency fC. Furthermore, frequency fD is slightly higher than the third harmonic frequency 3f0. That is, the resonant circuit based on inductor 116 and capacitor 118 and the resonant circuit based on inductor 122 and capacitor 120 operate as filters where the pass level drops the most at frequency fD. By aligning the frequency characteristics of the two resonant circuits, the pass level can be reduced over a wide bandwidth centered at the third harmonic frequency 3f0.

[0098] For reference Figure 11 As explained, frequency fC is slightly lower than the third harmonic frequency 3f0, and frequency fD is slightly higher than the third harmonic frequency 3f0. Frequency fC and frequency fD are slightly different. That is, the resonant frequencies of the first and second resonant circuits, which constitute the first and second filters, are slightly different.

[0099] When the fundamental frequency f0 of the signal output from amplifiers 104 and 105 is above f0_1 and below f0_2, the frequency of the third harmonic, i.e. the intermediate frequency fcenter2 between frequency fC and frequency fD, can be represented by equation (8).

[0100] fcenter2=(f0_1+f0_2) / 2×3……(8)

[0101] Moreover, the frequencies fC and fD can be expressed, for example, by equations (9) and (10).

[0102] fC≥fcenter2×0.9……(9)

[0103] fD≤fcenter2×1.1……(10)

[0104] (In-phase mode)

[0105] Figure 12 This is a diagram showing the differential amplifier circuit 100B in non-inverting mode. (See diagram for example.) Figure 12As shown, in non-inverting mode, it appears that a series resonant circuit based on inductor 106, capacitor 108, and inductor 114 is connected to the output of amplifier 104. Furthermore, it appears that the first terminal of inductor 106 is connected to the output of amplifier 104, and the first terminal of inductor 114 is connected to a reference potential. Also, in non-inverting mode, it appears that a series resonant circuit based on inductor 116, capacitor 118, and inductor 124 is connected to the output of amplifier 104. Furthermore, it appears that the second terminal of inductor 116 is connected to the output of amplifier 104, and the second terminal of inductor 124 is connected to a reference potential.

[0106] Furthermore, in non-inverting mode, it appears that a series resonant circuit based on inductor 112, capacitor 110, and inductor 114 is connected to the output of amplifier 105. Also, it appears that the first terminal of inductor 112 is connected to the output of amplifier 105, and the second terminal of inductor 114 is connected to a reference potential. Furthermore, in non-inverting mode, it appears that a series resonant circuit based on inductor 122, capacitor 120, and inductor 124 is connected to the output of amplifier 105. Also, it appears that the first terminal of inductor 122 is connected to the output of amplifier 105, and the second terminal of inductor 124 is connected to a reference potential.

[0107] In in-phase mode, inductor 106, capacitor 108, and inductor 114 operate as a resonant circuit. The resonant frequency of the resonant circuit based on inductor 106, capacitor 108, and inductor 114 is set as frequency fE. Frequency fE is a frequency slightly lower than the second harmonic frequency 2f0. If the inductance value of inductor 106 is set to L5, the capacitance value of capacitor 108 is set to C1, and the inductance value of inductor 114 is set to L2, then frequency fE can be expressed by equation (11).

[0108] fE=1 / 2π(C1×(L5+2L2))1 / 2……(11)

[0109] Since node N1 is the midpoint, the inductance value L7 of inductor 112 is equal to the inductance value L5 of inductor 106, and the capacitance value C3 of capacitor 110 is equal to the capacitance value C1 of capacitor 108. Therefore, the resonant frequency of the resonant circuit based on inductor 112, capacitor 110, and inductor 114 is frequency fE.

[0110] Furthermore, in the in-phase mode, inductor 116, capacitor 118, and inductor 124 operate as a resonant circuit. The resonant frequency of the resonant circuit based on inductor 116, capacitor 118, and inductor 124 is set as frequency fF. Frequency fF is a frequency slightly higher than the second harmonic frequency 2f0. If the inductance value of inductor 116 is set to L6, the capacitance value of capacitor 118 is set to C2, and the inductance value of inductor 124 is set to L3, then frequency fF can be expressed by equation (12).

[0111] fF=1 / 2π(C2×(L6+2L3))1 / 2……(12)

[0112] Since node N2 is the midpoint, the inductance value L8 of inductor 122 is equal to the inductance value L6 of inductor 116, and the capacitance value C4 of capacitor 120 is equal to the capacitance value C2 of capacitor 118. Therefore, the resonant frequency of the resonant circuit based on inductor 122, capacitor 120, and inductor 124 is frequency fF.

[0113] Figure 13 This is a graph showing the frequency characteristics in in-phase mode implemented by the differential amplifier circuit 100B. Figure 13 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. (See reference...) Figure 13 It can reduce the pass level in a wide bandwidth with a center frequency of 2f0, which is twice the wave frequency.

[0114] For reference Figure 13 As explained, frequency fE is slightly lower than the second harmonic frequency 2f0, and frequency fF is slightly higher than the second harmonic frequency 2f0. Frequency fE and frequency fF are slightly different. That is, the resonant frequencies of the first and second resonant circuits, which constitute the first and second filters, are slightly different.

[0115] When the fundamental frequency f0 of the signal output from amplifiers 104 and 105 is above f0_1 and below f0_2, the frequency of the 2-fold wave, i.e., the intermediate frequency fcenter3 between frequency fE and frequency fF, can be represented by equation (13).

[0116] fcenter3=(f0_1+f0_2) / 2×2……(13)

[0117] Moreover, the frequencies fE and fF can be expressed, for example, by equations (14) and (15).

[0118] fE≥fcenter3×0.9……(14)

[0119] fF≤fcenter3×1.1……(15)

[0120] Furthermore, the capacitance values ​​C1 of capacitor 108, C2 of capacitor 118, C3 of capacitor 110, and C4 of capacitor 120 are related in, for example, C1 and C3 > C2 and C4. Additionally, the inductance values ​​L2 of inductor 114 and L3 of inductor 124 are related in, for example, L2 < L3.

[0121] [Effect]

[0122] As described above, by using a first resonant circuit and a second resonant circuit with slightly different resonant frequencies, it is possible to make the frequency bands that decrease horizontally overlap. By making the two frequency bands of these resonant circuits overlap, thus achieving... Figure 13 As shown, it is possible to reduce the pass-through level for frequencies below and above the 2x wave frequency 2f0 as the center frequency.

[0123] (Third Implementation)

[0124] [Circuit Structure]

[0125] Figure 14 This diagram illustrates a third embodiment of the differential amplifier circuit of this disclosure. The differential amplifier circuit 100C of the third embodiment replaces the inductors 106, 112, 114, 116, 122, and 124 included in the differential amplifier circuit 100B of the second embodiment with microstrip lines or striplines. That is, each inductor is implemented using microstrip lines or striplines. The first terminal of inductor 106 is connected to the output of amplifier 104, and the second terminal is connected to the first terminal of capacitor 108. The first terminal of inductor 116 is connected to the output of amplifier 104, and the second terminal is connected to the first terminal of capacitor 118. The first terminal of inductor 112 is connected to the output of amplifier 105, and the second terminal is connected to the first terminal of capacitor 110. The first terminal of inductor 122 is connected to the output of amplifier 105, and the second terminal is connected to the first terminal of capacitor 120.

[0126] (Differential mode)

[0127] Figure 15 This is a diagram showing the differential amplifier circuit 100C in differential mode. (See diagram for example.) Figure 15 As shown, in differential mode, it appears that a series resonant circuit based on inductor 106 and capacitor 108 is connected between the output of amplifier 104 and node N1. Furthermore, in differential mode, it appears that a series resonant circuit based on inductor 116 and capacitor 118 is connected between the output of amplifier 104 and node N2.

[0128] In addition, such as Figure 15 As shown, in differential mode, with Figure 11Similarly, it appears that a series resonant circuit based on inductor 112 and capacitor 110 is connected between the output of amplifier 105 and node N1. Moreover, in differential mode, it appears that a series resonant circuit based on inductor 122 and capacitor 120 is connected between the output of amplifier 105 and node N2.

[0129] The resonant frequency of the resonant circuit based on inductor 106 and capacitor 108 is set as frequency fC. Frequency fC is slightly lower than the third harmonic frequency 3f0.

[0130] Node N1 is the midpoint, therefore the capacitance C3 of capacitor 110 is equal to the capacitance C1 of capacitor 108, and the inductance L7 of inductor 112 is equal to the inductance L5 of inductor 106. That is, the characteristic impedance and electrical length of the microstrip line and stripline of inductors 112 and 106 are equal, respectively. Therefore, the resonant frequency of the resonant circuit based on inductor 112 and capacitor 110 is frequency fC.

[0131] Furthermore, the resonant frequency of the resonant circuit based on inductor 116 and capacitor 118 is set as frequency fD. Frequency fD is a frequency slightly higher than the third harmonic frequency 3f0.

[0132] Node N2 is the midpoint, therefore the capacitance C4 of capacitor 120 is equal to the capacitance C2 of capacitor 118, and the inductance L8 of inductor 122 is equal to the inductance L6 of inductor 116. That is, the characteristic impedance and electrical length of the microstrip line and stripline of inductors 122 and 116 are equal, respectively. Therefore, the resonant frequency of the series resonant circuit of inductor 122 and capacitor 120 is frequency fD.

[0133] Figure 16 It is shown Figure 14 The frequency response of the differential amplifier circuit 100C in differential mode is shown in the figure. Figure 16 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. For example... Figure 16 As shown, by making the frequency characteristics of the two resonant circuits coincide, the pass level can be reduced in a wide frequency band with the 3rd harmonic frequency 3f0 as the center frequency.

[0134] (In-phase mode)

[0135] Figure 17 This is a diagram showing the differential amplifier circuit 100C in non-inverting mode. (See diagram for example.) Figure 17 As shown, in in-phase mode, and Figure 12Similarly, it appears that a series resonant circuit based on inductor 106, capacitor 108, and inductor 114 is connected to the output of amplifier 104. Moreover, in non-inverting mode, it appears that a series resonant circuit based on inductor 116, capacitor 118, and inductor 124 is connected to the output of amplifier 104.

[0136] Furthermore, in in-phase mode, with Figure 12 Similarly, it appears that a series resonant circuit based on inductor 112, capacitor 110, and inductor 114 is connected to the output of amplifier 105. Furthermore, in non-inverting mode, it appears that a series resonant circuit based on inductor 122, capacitor 120, and inductor 124 is connected to the output of amplifier 105. Moreover, it appears that the first terminal of inductor 122 is connected to the output of amplifier 105, and the second terminal of inductor 124 is connected to a reference potential.

[0137] In in-phase mode, inductor 106, capacitor 108, and inductor 114 operate as a resonant circuit. The resonant frequency of the resonant circuit based on inductor 106, capacitor 108, and inductor 114 is set as frequency fE. Frequency fE is a frequency slightly lower than the second harmonic frequency 2f0.

[0138] Node N1 is the midpoint, therefore the inductance value L7 of inductor 112 is equal to the inductance value L5 of inductor 106, and the capacitance value C3 of capacitor 110 is equal to the capacitance value C1 of capacitor 108. That is, the characteristic impedance and electrical length of the microstrip line and stripline of inductors 112 and 106 are equal, respectively. Therefore, the resonant frequency of the resonant circuit based on inductor 112, capacitor 110, and inductor 114 is frequency fE.

[0139] Furthermore, in in-phase mode, inductor 116, capacitor 118, and inductor 124 operate as a resonant circuit. The resonant frequency of the resonant circuit based on inductor 116, capacitor 118, and inductor 124 is set as frequency fF. Frequency fF is a frequency slightly higher than the second harmonic frequency 2f0.

[0140] Since node N2 is the midpoint, the inductance value L8 of inductor 122 is equal to the inductance value L6 of inductor 116, and the capacitance value C4 of capacitor 120 is equal to the capacitance value C2 of capacitor 118. Therefore, the resonant frequency of the resonant circuit based on inductor 122, capacitor 120, and inductor 124 is frequency fF.

[0141] Figure 18 It is shown by Figure 14 The graph shows the frequency response of the differential amplifier circuit 100C in non-inverting mode. Figure 18 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. (See reference...) Figure 18It can reduce the pass level in a wide bandwidth with a center frequency of 2f0, which is twice the wave frequency.

[0142] Alternatively, it can be set not to Figure 14 In the second embodiment, all inductors 106, 112, 114, 116, 122, and 124 are replaced with microstrip lines or striplines, or only a portion of them are replaced with microstrip lines or striplines. That is, at least one of the inductors 106, 112, 114, 116, 122, and 124 included in the differential amplifier circuit 100B is implemented using microstrip lines or striplines.

[0143] Furthermore, the capacitance values ​​C1 of capacitor 108, C2 of capacitor 118, C3 of capacitor 110, and C4 of capacitor 120 are related in, for example, C1 and C3 > C2 and C4. Additionally, the inductance values ​​L2 of inductor 114 and L3 of inductor 124 are related in, for example, L2 < L3.

[0144] [Effect]

[0145] As described above, by using a first resonant circuit and a second resonant circuit with slightly different resonant frequencies, it is possible to make the frequency bands that decrease horizontally overlap. By making the two frequency bands of these resonant circuits overlap, thus achieving... Figure 18 As shown, it can reduce the pass-through level for frequencies below and above the twice-wavelength frequency 2f0 as the center frequency.

[0146] (Fourth implementation)

[0147] [Circuit Structure]

[0148] Figure 19 This diagram illustrates a fourth embodiment of the differential amplifier circuit of this disclosure. The differential amplifier circuit 100D of the fourth embodiment, like the differential amplifier circuit 100B of the second embodiment, has a resonant circuit based on inductor 106, capacitor 108, and inductor 114, and a resonant circuit based on inductor 112, capacitor 110, and inductor 114. In the differential amplifier circuit 100D of the fourth embodiment, this resonant circuit serves as a first filter.

[0149] The differential amplifier circuit 100D of the fourth embodiment includes a capacitor 140. The first terminal of capacitor 140 is connected to the midpoint P1 of the inductor 132 in the primary winding of the balun 130a. The second terminal of capacitor 140 is connected to a reference potential. The inductor 132 of the balun 130a is magnetically coupled to the inductor 134. A resonant circuit is implemented by the inductor 132 and the capacitor 140. In the differential amplifier circuit 100D of the fourth embodiment, the resonant circuit based on the inductor 132, which forms the primary winding of the balun 130a, and the third capacitor 140, serves as a second filter.

[0150] The resonant frequency of the resonant circuit based on inductor 132 and capacitor 140 is higher than the resonant frequency of the resonant circuit based on inductor 106, capacitor 108, and inductor 114. The resonant frequency of the resonant circuit based on inductor 132 and capacitor 140 is higher than the resonant frequency of the resonant circuit based on inductor 112, capacitor 110, and inductor 114. Furthermore, the resonant circuits based on inductor 116, capacitor 118, and inductor 124 and the resonant circuits based on inductor 122, capacitor 120, and inductor 124 included in the differential amplifier circuit 100B of the second embodiment are not included in the differential amplifier circuit 100D. Therefore, the differential amplifier circuit 100D of the fourth embodiment can reduce the mounting area compared to the differential amplifier circuit 100B of the second embodiment.

[0151] (Differential mode)

[0152] Figure 20 This is a diagram showing the differential amplifier circuit 100D in differential mode. (See diagram for example.) Figure 20 As shown, in differential mode, with Figure 10 Similarly, it appears that a series resonant circuit based on inductor 106 and capacitor 108 is connected between the output of amplifier 104 and node N1. Moreover, in differential mode, it appears that a series resonant circuit based on inductor 112 and capacitor 110 is connected between the output of amplifier 105 and node N1.

[0153] Figure 21 It is shown by Figure 19 The graph shows the frequency response in differential mode implemented by the differential amplifier circuit. Figure 21 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. (See reference...) Figure 21 It can reduce the pass-through level in a frequency band centered at a frequency of 3 times the harmonic frequency 3f0.

[0154] (In-phase mode)

[0155] Figure 22 This is a diagram showing the differential amplifier circuit 100D in non-inverting mode. (See diagram for example.) Figure 22As shown, in in-phase mode, and Figure 12 Similarly, it appears that the output of amplifier 104 is connected to a series resonant circuit based on inductor 106, capacitor 108, and inductor 114, and also to a series resonant circuit based on inductor 132 and capacitor 140. Furthermore, in differential mode, it appears that the output of amplifier 105 is connected to a series resonant circuit based on inductor 112, capacitor 110, and inductor 114, and also to a series resonant circuit based on inductor 132 and capacitor 140.

[0156] Figure 23 It is shown by Figure 19 The graph shows the frequency response of the differential amplifier circuit implemented in non-inverting mode. Figure 23 In the diagram, the horizontal axis represents frequency, and the vertical axis represents the horizontal axis. (See reference...) Figure 23 It can reduce the pass level in a wide bandwidth with a center frequency of 2f0, which is twice the wave frequency.

[0157] (Fifth Embodiment)

[0158] Figure 24 This is a diagram illustrating a fifth embodiment of the differential amplifier circuit of this disclosure. Figure 24 Showing targets Figure 9 An example of the layout of the differential amplifier circuit 100B of the second embodiment shown.

[0159] [structure]

[0160] like Figure 24 As shown, in this example, an inductor 106 and a capacitor 108 are provided at the output of amplifier 104. Furthermore, an inductor 112 and a capacitor 110 are provided at the output of amplifier 105. An inductor 114 is provided near capacitors 108 and 110. "Near" refers to a position within a distance of 6 μm to 20 μm from capacitors 108 and 110. Additionally, an inductor 116 and a capacitor 118 are provided at the output of amplifier 104. Furthermore, an inductor 122 and a capacitor 120 are provided at the output of amplifier 105. An inductor 124 is provided near capacitors 118 and 120. A balun (not shown) is connected to the outputs of amplifiers 104 and 105.

[0161] exist Figure 24 In this configuration, inductors 106 and 112 can be arranged symmetrically. Furthermore, capacitors 108 and 110 can be arranged symmetrically. Therefore, as shown in reference... Figure 10 As explained, it can be achieved in differential mode. Figure 9 The node N1 shown is configured as the midpoint.

[0162] Similarly, inductors 116 and 122 can be configured symmetrically. Furthermore, capacitors 118 and 120 can be configured symmetrically. Therefore, as shown in the reference... Figure 10 As explained, it can be achieved in differential mode. Figure 9 The node N2 shown is configured as the midpoint.

[0163] [Effect]

[0164] By adopting Figure 24 The layout shown can achieve the reference Figure 9 The differential amplifier circuit 100B of the second embodiment described herein. Furthermore, it is possible to configure nodes N1 and N2 as midpoints in differential mode. Therefore, it is possible to achieve the reference... Figure 11 The frequency characteristics and reference in differential mode are described. Figure 13 The frequency characteristics in in-phase mode are explained.

[0165] The above is aimed at Figure 9 The layout of the differential amplifier circuit 100B in the second embodiment shown has been described, but for Figure 1 The differential amplifier circuit 100A of the first embodiment shown Figure 14 The differential amplifier circuit 100C of the third embodiment shown Figure 19 The differential amplifier circuit 100D of the fourth embodiment shown can also be configured to be symmetrical. Therefore, it is possible to configure nodes N1 and N2 as the midpoints.

Claims

1. A differential amplifier circuit, comprising: A differential amplifier that outputs signals containing high-order harmonics; and The first filter and the second filter reduce the level of even harmonics in the output of the differential amplifier. The first filter and the second filter are connected to the output of the differential amplifier. The center frequency of the first filter is lower than the center frequency of the even harmonic. The center frequency of the second filter is higher than the center frequency of the even harmonic.

2. The differential amplifier circuit according to claim 1, wherein, The first filter is a resonant circuit that includes a first capacitor and a first inductor. The second filter is a resonant circuit that includes a second capacitor and a second inductor. The capacitance value of the first capacitor is greater than the capacitance value of the second capacitor. The inductance value of the first inductor is less than the inductance value of the second inductor.

3. The differential amplifier circuit according to claim 2, wherein, The first filter also includes a third inductor. The third inductor, together with the first capacitor and the first inductor, operates as a resonant circuit. The second filter also includes a fourth inductor. The fourth inductor, together with the second capacitor and the second inductor, operates as a resonant circuit.

4. The differential amplifier circuit according to any one of claims 1 to 3, wherein, At least one of the inductors is implemented using microstrip lines and striplines.

5. The differential amplifier circuit according to any one of claims 1 to 3, wherein, The differential amplifier circuit further includes a balun, which is located at the output of the differential amplifier. The first filter and the second filter are provided between the differential amplifier and the balun.

6. The differential amplifier circuit according to any one of claims 1 to 3, wherein, The differential amplifier circuit further includes a balun, which is located at the output of the differential amplifier. The differential amplifier circuit further includes a third capacitor connected between the midpoint of the inductor that forms the primary winding of the balun and the reference potential. The resonant circuit based on the inductor that forms the primary winding and the third capacitor forms the second filter.

7. The differential amplifier circuit according to any one of claims 1 to 3, wherein, The center frequency of the first filter is 0.9 times the center frequency of the even harmonic. The center frequency of the second filter is 1.1 times the center frequency of the even harmonic.

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