Active balanced-unbalanced transformer circuit, power amplifier circuit and module

Abstract

The present invention provides an active balanced-unbalanced transformer circuit, a power amplifier circuit, and a power amplifier module that can suppress the area of ​​a semiconductor chip from increasing. The active balanced-unbalanced transformer circuit (10) includes: a transistor (Q1) and a transistor (Q2), the emitters of which are electrically connected to each other and output a differential signal; and a circuit element (30), which is connected between the connection point of the emitter of the transistor (Q1) and the emitter of the transistor (Q2) and a reference potential, and the impedance at a specific frequency of the input signal appears to be sufficiently greater than the impedance at other frequencies. The input signal of the input terminal (Pin) is applied to the base of the transistor (Q1), the reference potential is applied to the base of the transistor (Q2), and the power supply voltage (Vcc) is applied to the collectors of the transistor (Q1) and the transistor (Q2), and the signals of the collectors of the transistor (Q1) and the transistor (Q2) are output as the above-mentioned differential signal.

Description

Technical Field

[0001] The invention relates to an active balanced-unbalanced transformer circuit, a power amplifier circuit and a power amplifier module. Background Art

[0002] Conventionally, a balanced-unbalanced transformer formed by a differential transformer circuit is sometimes provided at the input stage or the output stage of an amplifier of a power amplifier circuit. Fig.18 (a) A structure in which a balun is provided at the output stage of an amplifier is disclosed.

[0003] Prior Art Literature

[0004] Non-patent literature

[0005] Non-patent document 1: Kyu Hwan An et al., "Power-Combining Transformer Techniques for Fully-Integrated CMOS Power Amplifiers", (USA), IEEE JOURNAL OF SOLID-STATE CIRCUITS, Institute of Electrical and Electronics Engineers, May 2008, Vol. 43, No. 5, pp. 1064-1075

[0006] Here, consider the case where a balun using a transformer circuit including passive elements is provided on a semiconductor chip together with a power amplifier circuit. In this case, if an inductor required for the balun is formed on the semiconductor chip, the area of ​​the semiconductor chip will increase. Summary of the invention

[0007] Problems to be solved by the invention

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to realize an active balun circuit, a power amplifier circuit, and a power amplifier module that can suppress an increase in the area of ​​a semiconductor chip.

[0009] Technical solutions to solve problems

[0010] An active balun circuit according to one aspect of the present invention is an active balun circuit, namely, comprising:

[0011] a first transistor and a second transistor; and

[0012] The impedance of a circuit element at a specific frequency of the input signal appears to be sufficiently greater than the impedance at other frequencies.

[0013] A pair of differential signals corresponding to the input signal are output from the first transistor and the second transistor.

[0014] An active balun circuit according to another aspect of the present invention is an active balun circuit comprising:

[0015] a first transistor including a first terminal connected to a reference potential via a circuit element, a second terminal connected to an input terminal, and a third terminal connected to a power supply voltage terminal; and

[0016] a second transistor including a first terminal connected to a reference potential via the circuit element, a second terminal connected to the reference potential, and a third terminal connected to the power supply voltage terminal,

[0017] The first terminal of the first transistor is a source or a drain,

[0018] The second terminal of the first transistor is a gate,

[0019] The third terminal of the first transistor is a drain or a source,

[0020] The first terminal of the second transistor is a source or a drain,

[0021] The second terminal of the second transistor is a gate,

[0022] The third terminal of the second transistor is a drain or a source,

[0023] A pair of differential signals is output from the third terminal of the first transistor and the third terminal of the second transistor.

[0024] Effects of the Invention

[0025] According to the present invention, it is possible to provide an active balun circuit capable of suppressing an increase in the area of ​​a semiconductor chip, a power amplifier circuit including the active balun circuit, and a power amplifier module. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a diagram showing a power amplifier circuit including a balun.

[0027] Figure 2 : is a diagram showing an example of a power amplifier circuit including an active balun circuit.

[0028] Figure 3 It is shown Figure 2 This is a Smith chart showing an example of impedance when the circuit elements are resistors.

[0029] Figure 4 is a diagram showing a reference example of an active balun circuit.

[0030] Figure 5 It shows that the Figure 4 Graph showing characteristics of a power amplifier circuit of an active balun circuit according to a reference example.

[0031] Figure 6 It shows that the Figure 4 Graph showing characteristics of a power amplifier circuit of an active balun circuit according to a reference example.

[0032] Figure 7 It shows that the Figure 4 Graph showing characteristics of a power amplifier circuit of an active balun circuit according to a reference example.

[0033] Figure 8 It shows that the Figure 4 Graph showing characteristics of a power amplifier circuit of an active balun circuit according to a reference example.

[0034] Fig. 9 is a diagram showing another example of an active balun circuit.

[0035] Fig.10 It is shown Fig. 9 A Smith chart showing an example of impedance when the circuit element is an inductor.

[0036] Fig.11 It shows that the Fig. 9 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0037] Fig.12 It shows that the Fig. 9 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0038] Fig.13 It shows that the Fig. 9 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0039] Fig.14 It shows that the Fig. 9 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0040] Fig.15is a diagram showing another example of an active balun circuit.

[0041] Fig.16 It shows that the Fig.15 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0042] Fig.17 It shows that the Fig.15 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0043] Fig.18 It shows that the Fig.15 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0044] Fig.19 It shows that the Fig.15 A graph showing the characteristics of a power amplifier circuit with an active balun circuit.

[0045] Fig. 20 It is shown Figure 2 A diagram of a modified example of the power amplifier circuit shown.

[0046] Fig.21 is a diagram showing an example of a power amplifier module including a semiconductor chip having an active balun circuit of the present disclosure.

[0047] Fig. 22 is a diagram showing another example of a power amplification module including a semiconductor chip having the active balun circuit of the present disclosure.

[0048] Fig.23 FIG. 2 is a diagram showing an example of an equivalent circuit of an active balun circuit using a distributed constant circuit.

[0049] Description of Reference Numerals

[0050] 10, 10a, 10b, 10c, 10d, 10e: active balun circuit;

[0051] 11, 12, 13: amplifier;

[0052] 30, 30a, 30b, 30c; circuit elements;

[0053] 41, 42: Wiring;

[0054] 100: semiconductor chips;

[0055] Pin: input terminal;

[0056] Pout: output terminal;

[0057] Q1: transistor;

[0058] Q2: transistor;

[0059] T1, T2: Transmission line transformers. DETAILED DESCRIPTION

[0060] Hereinafter, an embodiment of the active balanced-unbalanced transformer circuit disclosed in the present invention is described in detail based on the accompanying drawings. In addition, the present invention is not limited to the embodiment. In addition, the constituent elements of each embodiment include constituent elements that can be and easily replaced by those skilled in the art, or substantially the same constituent elements. Each embodiment is an example, and partial replacement or combination of the structures shown in different embodiments can be performed. After the second embodiment, the description of matters common to the first embodiment is omitted, and only the differences are described. In particular, the same effects based on the same structure will not be mentioned one by one in each embodiment.

[0061] The following describes an active balanced-unbalanced transformer circuit of the present disclosure. The active balanced-unbalanced transformer circuit of the present disclosure is different from a balanced-unbalanced transformer formed by a differential transformer circuit, and does not use a wiring inductor of a winding. In order to make each embodiment easy to understand, a power amplifier circuit including a balanced-unbalanced transformer formed by a differential transformer circuit is first described as a comparative example.

[0062] (Comparative Example)

[0063] [Circuit structure]

[0064] Figure 1 is a diagram showing a power amplifier circuit including a balun. Figure 1 The power amplifier circuit shown includes a balanced-unbalanced transformer B formed by a transformer circuit using a wiring inductor of a winding. The balanced-unbalanced transformer B is provided between nodes N1 and N2 on the input side of a pair of amplifiers 11 and 12 at the final stage and an amplifier 13 at the preceding stage. On the output side of the pair of amplifiers 11 and 12, a transformer T and a filter formed by an inductor L and a capacitor C are provided. The midpoint of the primary winding of the transformer T is connected to a power supply voltage Vcc. The capacitors CP1 and CP2 electrically connected between the midpoint of the primary winding of the transformer T and a reference potential, respectively, function as bypass capacitors. As for the reference potential, a ground potential can be exemplified, but the present disclosure is not limited thereto.

[0065] [action]

[0066] The signal input to the input terminal Pin, for example, an RF (Radio Frequency) signal is amplified by the amplifier 13 and input to the balanced-unbalanced transformer B. Through the balanced-unbalanced transformer B, a differential output can be obtained at nodes N1 and N2. The differential outputs of nodes N1 and N2 are amplified by amplifiers 11 and 12. The outputs of the amplifiers 11 and 12 are output to the output terminal Pout via a transformer T and a filter formed by an inductor L and a capacitor C. In this comparative example, by providing a balanced-unbalanced transformer B between the stages, the final stage formed by the amplifiers 11 and 12 and the previous stage formed by the amplifier 13 can be separated, and a differential output can be obtained.

[0067] In referring to Figure 1 When the power amplifier circuit of the comparative example described above is implemented as a semiconductor chip, the area of ​​the semiconductor chip increases due to the balun transformer B. Therefore, in the power amplifier circuit of the comparative example, it is difficult to reduce the area of ​​the entire semiconductor chip.

[0068] (First embodiment)

[0069] [Circuit structure]

[0070] Figure 2 1 is a diagram showing an example of a power amplifier circuit including an active balun circuit. Figure 2 As shown, an active balun circuit 10 is provided between an input terminal Pin and nodes N1 and N2 on the input side of a pair of amplifiers 11 and 12 .

[0071] The active balun circuit 10 includes a transistor Q1 as a first transistor, a transistor Q2 as a second transistor, and a circuit element 30. The transistors Q1 and Q2 have an emitter as a first terminal, a base as a second terminal, and a collector as a third terminal. The active balun circuit 10 is not a balun including a winding inductor, but is a balun implemented by the transistors Q1, Q2, and the circuit element 30.

[0072] The base of transistor Q1 is connected to input terminal Pin. The base of transistor Q2 is connected to a reference potential. As for the reference potential, a ground potential can be exemplified, but the present disclosure is not limited thereto. The emitter of transistor Q1 is connected to the emitter of transistor Q2, and their connection point is connected to one end of circuit element 30. The other end of circuit element 30 is connected to the reference potential. The collector of transistor Q1 and the collector of transistor Q2 are connected to power supply voltage Vcc.

[0073] The signal Pi of the collector of the transistor Q1 and the signal Ph of the collector of the transistor Q2 become a pair of differential signals. The signal Pi of the collector of the transistor Q1 is input to the amplifier 11 via a filter formed by the inductor L1 and the capacitor C1. The wiring 41 and the capacitor C41 function as a matching circuit. The signal Ph of the collector of the transistor Q2 is input to the amplifier 12 via a filter formed by the inductor L2 and the capacitor C2. The wiring 42 and the capacitor C42 function as a matching circuit.

[0074] The transistors Q1 and Q2 may be NPN transistors, but the present disclosure is not limited thereto. The transistors Q1 and Q2 may be PNP transistors.

[0075] In addition, in the present disclosure, each transistor is set as a bipolar transistor, but the present disclosure is not limited to this. Regarding the bipolar transistor, a heterojunction bipolar transistor (HBT) can be exemplified, but the present disclosure is not limited to this. Each transistor can also be a field effect transistor (FET), for example. In this case, it is sufficient to replace the collector with the drain, the base with the gate, and the emitter with the source. Therefore, the above-mentioned first terminal can also be called an emitter or a source, the above-mentioned second terminal can also be called a base or a gate, and the above-mentioned third terminal can also be called a collector or a drain.

[0076] Each transistor may be a multi-finger transistor in which a plurality of unit transistors (also referred to as "fingers") are electrically connected in parallel. The so-called unit transistor refers to the minimum structure constituting a transistor.

[0077] The circuit element 30 includes, for example, at least one of a wiring of a specific length, an inductor, a capacitor, and a resistor. The circuit element 30 can also be called an impedance element. The circuit element 30 preferably has a high impedance at the fundamental frequency of the input signal. The circuit element 30 preferably has a large impedance at the fundamental frequency. That is, preferably, the impedance of the circuit element 30 at a specific frequency of the input signal appears to be sufficiently greater than the impedance at other frequencies. However, the impedance of the circuit element 30 appears to be large only when the power amplifier circuit does not oscillate.

[0078] Figure 3 : is a Smith chart showing an example of impedance when the circuit element 30 is a resistor. When the frequency is changed from 1.930 GHz to 1.950 GHz, the impedance value ( Figure 3 The circle mark in the Figure 3The impedance at point ml at a frequency of 1.950 GHz is 540 Ω, which is about 10 times the value of 50 Ω. Therefore, it can be said that the impedance appears to be sufficiently large.

[0079] Here, a case where the circuit element 30 is a wiring will be described. Figure 4 : is a diagram showing an active balun circuit 10a as a reference example. Figure 4 The active balun circuit 10a shown includes a wiring 30h as the circuit element 30. Therefore, a connection point between the emitter of the transistor Q1 and the emitter of the transistor Q2 is electrically connected to a reference potential via the wiring 30h. Figure 4 The active balun circuit 10a shown does not include a transformer circuit using a wiring inductor of a winding. Therefore, by using the active balun circuit 10a in a power amplifier circuit, the area of ​​a semiconductor chip can be reduced.

[0080] [action]

[0081] Figures 5 to 8 It shows that the Figure 4 Graph showing characteristics of a power amplifier circuit of an active balun circuit 10a according to a reference example. Figure 5 It is shown that Figure 4 The active balun circuit 10a of the reference example shown is used for Figure 2 In the case of a power amplifier circuit Figure 2 Graph of the characteristics obtained at nodes N1 and N2 in .

[0082] Figure 5 : shows the relationship between the level of the signal Pi at the node N1 and the level of the signal Ph at the node N2 with respect to the level of the input signal of the input terminal Pin. Figure 5 In the example, when the level of the input signal of the input terminal Pin changes, the level of the signal Pi changes in the same way as the level of the signal Ph. Figure 5 As shown, the level of signal Pi and the level of signal Ph differ, and signal Pi and signal Ph become differential signals with unbalanced amplitudes. In addition, the so-called unbalanced in the present disclosure is defined as the phase difference being independent of the level of the input signal and not fixed, or the amplitude being not output in proportion to the level of the input signal. On the other hand, the so-called balanced is defined as the phase difference being independent of the level of the input signal and fixed, and the amplitude being output in proportion to the level of the input signal.

[0083] Figure 6 The relationship between the level of the input signal of the input terminal Pin and the phase changes of the signal Pi and the signal Ph is shown. Figure 7The relationship between the level of the input signal of the input terminal Pin and the phase difference between the signal Pi and the signal Ph is shown. The signal Pi and the signal Ph as differential signals preferably have a phase difference of 180°. Figure 6 as well as Figure 7 It can be understood that the phase difference between the signal Pi and the signal Ph is approximately 130°, and the phase difference between the signal Pi and the signal Ph deviates from 180°.

[0084] Figure 8 The relationship between the level of the signal at the output terminal Pout and the gain of the power amplifier circuit is shown. The signal Pi and the signal Ph become differential signals, that is, the differential transformer circuit that synthesizes the phase from the 180° phase difference on the output matching side to the same phase has a phase deviation from 180°, and its output is unbalanced. Therefore, the two output stage transistors cannot be driven separately under the optimal load conditions, and the output stage of the differential amplifier becomes a load operation state in which the desired saturated output cannot be obtained. Therefore, as Figure 8 As shown in FIG. 1 , if the signal at the output terminal Pout exceeds 25 [dBm], the gain starts to decrease, and thereafter, the gain decreases sharply. Figure 4 In the active balun circuit 10a of the reference example shown in the figure, it is not possible to drive the two output stage transistors Q1 and Q2 under the optimum load conditions. Figure 4 The active balun circuit 10a of the reference example shown here can operate normally as a power amplifier circuit.

[0085] [Effect]

[0086] Reference Figure 2 The active balun circuit 10a is illustrated with Figure 1 Unlike the balun B shown, a transformer circuit using a wiring inductor of a winding is not included. Therefore, by adopting the active balun circuit 10a in the power amplifier circuit, it is possible to suppress an increase in the area of ​​a semiconductor chip.

[0087] (Second embodiment)

[0088] [Circuit structure]

[0089] Fig. 9 is a diagram showing another example of an active balun circuit 10b. Fig. 9 The active balun circuit 10b shown is Figure 4Compared with the active balanced-unbalanced transformer circuit 10a shown in FIG. 1 , the active balanced-unbalanced transformer circuit 10b includes a circuit element 30a. The active balanced-unbalanced transformer circuit 10b is not a balanced-unbalanced transformer including a winding inductor, but a balanced-unbalanced transformer implemented by transistors Q1, Q2 and the circuit element 30a. The connection point between the emitter of transistor Q1 and the emitter of transistor Q2 is connected to one end of the circuit element 30a. Figure 4 The circuit configuration of is different in that the circuit element 30a includes the inductor L3. Therefore, the connection point between the emitter of the transistor Q1 and the emitter of the transistor Q2 is connected to the reference potential via the inductor L3.

[0090] The inductance value of the inductor L3 is selected so that the impedance of the fundamental wave of the circuit element 30a becomes sufficiently large within a range where it does not oscillate at the fundamental frequency. When the circuit element 30a is formed in a semiconductor chip, the length of the wiring, etc. can be adjusted in micrometer units, for example. Therefore, the required impedance at the fundamental wave can be easily achieved. For example, at a fundamental frequency of 2 GHz, the inductance value of the inductor L3 is about 5.13 nH.

[0091] Fig.10 It is shown Fig. 9 The Smith chart of the impedance example when the circuit element 30a in FIG. 1 is the inductor L3. When the frequency is changed from 1.930 GHz to 1.950 GHz, the normalized impedance value ( Fig.10 The short line in Fig.10 The impedance at point m2 at a frequency of 1.950 GHz is 516Ω, which is about 10 times the value of 50Ω. Therefore, it can be said that the impedance appears to be sufficiently large.

[0092] [action]

[0093] Figures 11 to 14 It shows that the Fig. 9 Graph showing characteristics of a power amplifier circuit of the active balun circuit 10b. Fig.11 It is shown that Fig. 9 The active balun circuit 10b is shown for use in Figure 2 In the case of a power amplifier circuit Figure 2 Graph of the characteristics obtained at nodes N1 and N2 in .

[0094] Fig.11 : shows the relationship between the level of the signal Pi at the node N1 and the level of the signal Ph at the node N2 with respect to the level of the input signal of the input terminal Pin. Fig.11In FIG. 1 , when the level of the input signal of the input terminal Pin changes, the level of the signal Pi changes in the same manner as the level of the signal Ph. Since the signal Pi and the signal Ph are differential signals, they are preferably at the same level. Fig.11 and Figure 5 , the difference between the level of the signal Pi and the level of the signal Ph is small, and the state of the imbalance of the amplitudes of the signal Pi and the signal Ph is improved. Thus, the symmetry of the differential signal can be satisfied.

[0095] Fig.12 The relationship between the level of the input signal of the input terminal Pin and the phase changes of the signal Pi and the signal Ph is shown. Fig.13 The relationship between the level of the input signal of the input terminal Pin and the phase difference between the signal Pi and the signal Ph is shown. Fig.12 as well as Fig.13 It can be understood that the phase difference between the signal Pi and the signal Ph is close to 180°. Figure 6 as well as Figure 7 Compared with the case of , the phase difference between the signal Pi and the signal Ph is improved. Figure 4 Compared with the active balanced-unbalanced transformer of the structure, Fig. 9 In an active balun transformer having a structure of , even if the input level of the input signal changes, the phases of the signals Pi and Ph also change in the same manner. Therefore, as a phase difference, even if the input signal changes, a fixed phase difference can always be achieved, and its value can be maintained at a phase difference close to 180°.

[0096] Fig.14 The relationship between the level of the signal at the output terminal Pout and the gain of the power amplifier circuit is shown. Fig.14 As shown in FIG. 1 , when the signal at the output terminal Pout exceeds 20 [dBm], the gain starts to decrease, and thereafter the gain decreases rapidly. According to the third embodiment described below, this rapid decrease in gain can be improved.

[0097] Like reference Fig.11 As described above, the state of the imbalance of the amplitudes of the signal Pi and the signal Ph is improved, and as shown in FIG. Fig.12 as well as Fig.13 As described above, the phase difference between the signal Pi and the signal Ph is improved.

[0098] [Effect]

[0099] Active balun circuit 10b and Figure 1Unlike the balun B shown in the figure, the active balun circuit 10b does not include a transformer circuit using a wiring inductor of a winding. In addition, the area of ​​the wiring inductor used in the active balun circuit 10b can be made much smaller than the area of ​​the balun B including a combination of complex wiring transformer circuits. Therefore, by adopting the active balun circuit 10b in the power amplifier circuit, it is possible to suppress the increase in the area of ​​the semiconductor chip.

[0100] Furthermore, when a balun is formed on a semiconductor chip, there are certain limitations in the process regarding the number of wiring layers, dielectric film thickness, etc. used to form the balun, and in order to form a high-performance balun, the process cost may increase due to the increase in the number of masks, etc. In this regard, according to the active balun circuit 10b, it is possible to prevent the cost from increasing. Furthermore, the active balun circuit 10b can reduce the level difference of the output differential signal and improve the phase difference of the differential signal compared with the active balun circuit 10a.

[0101] (Third embodiment)

[0102] [Circuit structure]

[0103] Fig.15 is a diagram showing an example of an active balun circuit 10c. Fig.15 The active balanced-unbalanced transformer circuit 10c shown includes a circuit element 30b. The active balanced-unbalanced transformer circuit 10c is not a balanced-unbalanced transformer including a winding inductor, but a balanced-unbalanced transformer implemented by transistors Q1, Q2 and circuit element 30b. The connection point between the emitter of transistor Q1 and the emitter of transistor Q2 is connected to one end of circuit element 30b. Unlike the first embodiment and the second embodiment, circuit element 30b includes an inductor L3 and a capacitor C3. The inductor L3 and the capacitor C3 are connected in parallel between the emitter of transistor Q1 and the emitter of transistor Q2 and the reference potential. A parallel resonant circuit (tank circuit) is formed by the inductor L3 and the capacitor C3. The inductance value and the capacitance value can be appropriately determined so that the resonant frequency of the parallel resonant circuit is set to a specific frequency and the emitter impedance of the transistor is set to a desired size.

[0104] Through the resonance of the parallel circuit of inductor L3 and capacitor C3, the characteristic impedance of circuit element 30b becomes infinite at the base frequency. When circuit element 30b is formed in a semiconductor chip, the length of the wiring, etc. can be adjusted in nanometer units, for example. Therefore, the desired characteristic impedance can be easily achieved. For example, at a base frequency of 2GHz, the inductance value of inductor L3 is approximately 0.98nH, and the capacitance value of capacitor C3 is approximately 6pF. By setting the above values, the resonant frequency becomes 2GHz, which can be regarded as a sufficiently large impedance at an ideal 2GHz. The so-called sufficiently large impedance described here is defined as an impedance that is more than 10 times the standardized impedance when considering the standardized impedance. That is to say, in the case where circuit element 30b includes inductor L3 and capacitor C3, it is also the same as reference. Fig.10 In the example of impedance described above, it can be said that the impedance appears to be sufficiently large.

[0105] [action]

[0106] Figures 16 to 19 It shows that the Fig.15 Graph showing characteristics of a power amplifier circuit of the active balun circuit 10c. Fig.16 It is shown that Fig.15 The active balun circuit 10c shown is used for Figure 2 In the case of a power amplifier circuit Figure 2 Graph of the characteristics obtained at nodes N1 and N2 in .

[0107] Fig.16 : shows the relationship between the level of the signal Pi at the node N1 and the level of the signal Ph at the node N2 with respect to the level of the input signal of the input terminal Pin. Fig.16 In the embodiment, when the level of the input signal of the input terminal Pin changes, the level of the signal Pi and the level of the signal Ph change in the same manner. Since the difference between the level of the signal Pi and the level of the signal Ph is very small, the state of the amplitude imbalance between the signal Pi and the signal Ph is improved. Thus, the symmetry of the differential signal can be satisfied.

[0108] Fig.17 The relationship between the level of the input signal of the input terminal Pin and the phase changes of the signal Pi and the signal Ph is shown. Fig.18 The relationship between the level of the input signal of the input terminal Pin and the phase difference between the signal Pi and the signal Ph is shown. Fig.17 as well as Fig.18 It can be understood that the signal Pi and the signal Ph change similarly with respect to the change in the signal level of the input signal, so the phase difference between the signal Pi and the signal Ph is very close to 180. Therefore, the phase difference between the signal Pi and the signal Ph is further improved.

[0109] Fig.19 The relationship between the level of the signal at the output terminal Pout and the gain of the power amplifier circuit is shown. Fig.19 As shown in FIG. 1 , even when the level of the signal at the output terminal Pout is 30 (dBm), the gain hardly decreases, and a good characteristic can be obtained. Fig.17 as well as Fig.18 As explained above, the phase difference between the signal Pi and the signal Ph can be kept close to 180°, and the signal levels of the two signals are also approximately equal. Therefore, the subsequent two output stage transistors can be driven under the optimal load conditions. As a result, the differential amplifier as a whole of the two-stage structure is Fig.19 As shown, it becomes the action under ideal load conditions.

[0110] This point will be described by comparing with the second embodiment. Fig.14 As shown in FIG. 1 , the gain drops sharply due to the resistance component of the inductor L3 of the circuit element 30a. That is, in the second embodiment, as shown in FIG. Fig.12 as well as Fig.13 As explained above, the phase difference between the signal Pi and the signal Ph is improved. However, since the desired inductance value of the inductor L3 is large, the resistance component accompanying the increase in the wiring length is also very large, resulting in an increase in the emitter resistance of the driver transistor. Figure 5 and Fig.11 The comparison of the input-output characteristics of the amplifier also shows that the gain of the driver stage itself is greatly reduced. Therefore, the transistors in the output stage cannot be fully driven, and the gain of the amplifier as a whole is reduced. Fig.14 As shown in FIG. 1 , the gain drops sharply due to the resistance component of the inductor L3 of the circuit element 30a. Fig.19 As shown, even when the level of the signal at the output terminal Pout is 30 (dBm), the gain hardly decreases, and good characteristics can be obtained.

[0111] [Effect]

[0112] Active balun circuit 10c and Figure 1Unlike the balun B shown in FIG. 1 , the balun B does not include a transformer circuit using a wiring inductor of a winding. Therefore, by adopting the active balun circuit 10c in the power amplifier circuit, it is possible to suppress the increase in the area of ​​the semiconductor chip. Furthermore, compared with the active balun circuit 10b, the level difference of the output differential signal can be reduced, and the phase difference of the differential signal can be improved, and a good gain characteristic can be obtained. Compared with a structure with only a wiring inductor, the LC energy storage circuit can reduce the area by combining an inductor and a capacitor. Therefore, by using the active balun circuit 10c, the circuit can be miniaturized.

[0113] Modifications of the active balun circuit described above will be described below.

[0114] (Variant 1)

[0115] Fig. 20 It is shown Figure 2 FIG. 1 is a diagram showing a modified example of a power amplifier circuit. Fig. 20 In the active balun circuit 10d, the circuit element 30b and Fig.15 The active balun circuit 10c shown similarly includes an inductor L3 and a capacitor C3. The inductor L3 and the capacitor C3 are connected in parallel between the emitter of the transistor Q1 and the emitter of the transistor Q2 and the reference potential. The impedance of the circuit element 30b can be set large at the fundamental frequency by resonance of the parallel circuit of the inductor L3 and the capacitor C3.

[0116] In addition, the active balanced-unbalanced transformer circuit 10d of the power amplifier circuit of this example has transmission line transformers (Transmission Line Transformer) T1 and T2. The transmission line transformers T1 and T2 are provided between the final stage formed by a pair of amplifiers 11 and 12 and the previous stage thereof, that is, provided in the transmission paths 110 and 120 between the stages. That is, the transmission line transformers T1 and T2 are provided in the transmission paths 110 and 120 of a pair of differential signals. The transmission line transformers T1 and T2 make the magnetic field generated in the transmission line act as a transformer, and have the function of a matching circuit with an impedance conversion function. By not adopting Figure 1 The balun B including the windings shown creates a margin in the layout of the semiconductor chip, so that the transmission line transformers T1 and T2 can be provided on the semiconductor chip.

[0117] The transmission line transformer T1 includes wirings 511 and 512. The wiring 511 is connected in series between the collector of the transistor Q1 and the amplifier 11. The wiring 512 and the wiring 511 are arranged adjacent to each other. One end of the wiring 512 is connected to one end of the wiring 511, and the other end of the wiring 512 is connected to the power supply voltage Vcc. In addition, the capacitor C41 functions as a bypass capacitor.

[0118] The transmission line transformer T2 includes wirings 521 and 522. The wiring 521 is connected in series between the collector of the transistor Q2 and the amplifier 12. The wiring 522 and the wiring 521 are arranged adjacent to each other. One end of the wiring 522 is connected to one end of the wiring 521, and the other end of the wiring 522 is connected to the power supply voltage Vcc. In addition, the capacitor C42 functions as a bypass capacitor.

[0119] Generally, by combining transmission line transformers T1 and T2 in a power amplifier circuit, it is possible to easily achieve wideband and low-loss impedance matching of transistors Q1 and Q2 and amplifiers 11 and 12. As a result, a high-performance power amplifier circuit having a wider frequency band and high gain characteristics can be realized. In addition, the above configuration is such that transmission line transformers T1 and T2 are provided in the inter-stage transmission paths 110 and 120, but a configuration may also be such that a transmission line transformer and a balanced-unbalanced transformer are provided on the output matching side after the output stage transistor.

[0120] (Variant 2)

[0121] Fig.21 is a diagram showing an example of a power amplifier module including a semiconductor chip having an active balun circuit of the present disclosure. Fig.21 In the power amplifier module shown, the semiconductor chip 100 has the active balun circuit of the present disclosure. However, among the components of the active balun circuit, the circuit element 30 is formed on the multilayer substrate 200 as described below. Fig.21 The structure of each layer is schematically shown.

[0122] like Fig.21 As shown, the semiconductor chip 100 has an active balun region AB in which an active balun circuit is formed and an amplifier circuit region PS in which an amplifier circuit is formed. In addition, the semiconductor chip 100 has bumps 101a and 101b. The bumps 101a and 101b are, for example, CPB (Copper Pillar Bump), but are not limited thereto.

[0123] In addition, the multilayer substrate 200 has dielectric layers 201, 202, and 203. The dielectric layer 201 has electrodes 211 and 212 provided at positions corresponding to the bumps 101a and 101b. The semiconductor chip 100 is electrically connected to the corresponding electrodes 211 and 212 through the bumps 101a and 101b. The electrode 212 is connected to vias 215a, 215b, and 215c penetrating the dielectric layers 201, 202, and 203.

[0124] The dielectric layer 202 has an electrode 213 at a position opposite to a part of the electrode 211. The electrode 211 and the electrode 213 are opposite to each other with the dielectric layer 201 interposed therebetween, and they function as a capacitor C3. A via 214a penetrating the dielectric layers 202 and 203 is connected to the electrode 213. In addition, a via 214b penetrating the dielectric layers 201, 202, and 203 is connected to the electrode 211. The via 214b functions as an inductor L3 in a high frequency band. The inductor L3 is not limited to being formed by the via 214b, and may also be formed by a conductive wiring connected to the via 214b.

[0125] Through the above structure, the semiconductor chip 100 is electrically connected to the multilayer substrate 200. Moreover, instead of providing the circuit element 30 in the active balun circuit, the circuit element 30 is formed by the multilayer substrate 200. In this case, the semiconductor chip 100 includes a portion of the active balun circuit other than the circuit element 30, and the multilayer substrate 200 forms the circuit element 30 including the inductor L3 and the capacitor C3. That is, the multilayer substrate 200 has the circuit element 30 as one of the components of the active balun circuit, and the circuit element 30 required in the active balun circuit can be provided outside the active balun circuit. Thus, the semiconductor chip 100 can be reduced in size. In addition, in this example, for example, Fig.10 Likewise, the impedance of circuit element 30 appears to be sufficiently large at the fundamental frequency.

[0126] (Variant 3)

[0127] Fig. 22 is a diagram showing another example of a power amplifier module including a semiconductor chip having an active balun circuit of the present disclosure. Fig. 22 In the power amplifier module shown, the semiconductor chip 300 has the active balun circuit of the present disclosure. However, among the components of the active balun circuit, the circuit element 30 is formed on the multilayer substrate 200 as described below. Fig. 22 The structure of each layer is schematically shown.

[0128] like Fig. 22As shown, the semiconductor chip 300 has an active balun region AB in which an active balun circuit is formed and an amplifier circuit region PS in which an amplifier circuit of an output stage is formed. In addition, the semiconductor chip 300 has electrodes 216, 217, and 218. The electrode 218 is electrically connected to the electrode 216 formed on the back side of the semiconductor chip 300 through vias 219a and 219b that penetrate the semiconductor chip 300. The electrode 216 is electrically connected to the vias 215a, 215b, and 215c. The transistors of the output stage generally handle large power, so the vias 215a, 215b, and 215c also play a role as thermal vias with a heat dissipation effect. The electrode 217 is electrically connected to the electrode 211 formed on the surface of the dielectric layer 201 through the bonding wire W1. The electrode 218 is electrically connected to the electrode 212a formed on the surface of the dielectric layer 201 through the bonding wire W2.

[0129] and Fig.21 Similarly to the case of , the electrode 211 faces the electrode 213 via the dielectric layer 201, and they function as a capacitor C3. Fig.21 Similarly to the case of , a via 214b is connected to the electrode 211. The via 214b functions as an inductor L3 in a high frequency band.

[0130] Through the above structure, the semiconductor chip 300 is electrically connected to the multilayer substrate 200. Moreover, instead of setting the circuit element 30 in the active balun circuit, it is constituted by the multilayer substrate 200. In this case, the semiconductor chip 300 includes the portion of the active balun circuit other than the circuit element 30, and the multilayer substrate 200 constitutes the circuit element 30 including the inductor L3 and the capacitor C3. That is, the multilayer substrate 200 has the circuit element 30 as one of the components of the active balun circuit, and the circuit element 30 required in the active balun circuit can be set outside the active balun circuit. Thus, the semiconductor chip 300 can be reduced in size. In addition, compared with the semiconductor chip 300, the manufacturing process of the multilayer substrate 200 is short, so the design cycle can be shortened. In addition, the characteristics can be fine-tuned by using the bonding leads together, adjusting the mounting position, etc. In addition, in this example, for example, it is also possible to Fig.10 Likewise, the impedance of circuit element 30 appears to be sufficiently large at the fundamental frequency.

[0131] (Variant 4)

[0132] In the second and third embodiments described above, the circuit elements 30a and 30b are lumped constant circuits. The present disclosure is not limited to lumped constant circuits, and circuit elements that are distributed constant circuits may also be used. For example, in Figure 4A wiring 30h having a given distance from the connection point between the emitters of transistor Q1 and transistor Q2 to the reference potential. If parasitic wiring capacitance and parasitic wiring inductance are taken into consideration, it can be considered that a distributed constant circuit is formed by wiring 30h. Therefore, it can be considered that wiring 30h is a distributed constant circuit with a given characteristic impedance. Therefore, instead of using circuit elements 30a and 30b as lumped constant circuits, high impedance can be achieved by wiring from the connection point between the emitters to the reference potential according to the fundamental frequency. If the wavelength of the fundamental frequency is set to λ, wiring 30h is preferably λ / 4 in length. That is, at the fundamental frequency, wiring 30h having a length of 1 / 4 wavelength is set as a circuit element. In addition, because there is a wavelength shortening effect caused by the relative dielectric constant of the semiconductor substrate, it is not 1 / 4 wavelength in free space, but 1 / 4 wavelength as electrical length. For example, when the fundamental frequency is 30GHz to 650MHz, λ / 4 is about 0.7 [mm] to about 58 [mm]. In addition, the length of the wiring 30h is not limited to 1 / 4 wavelength, and may be n / 4 wavelength (n is an odd number greater than or equal to 3).

[0133] Fig.23 FIG. 1 is a diagram showing an example of an equivalent circuit of an active balun circuit using a distributed constant circuit. Fig.23 In FIG. 1 , a circuit element 30c formed of wiring as a distributed constant circuit exists between a connection point between the emitter of the transistor Q1 and the emitter of the transistor Q2 and a reference potential. The impedance of the circuit element 30c appears to be sufficiently large at the fundamental frequency. Fig.23 The active balun circuit 10e shown is not a balun including a winding inductor, but is a balun implemented by transistors Q1, Q2 and circuit element 30c.

[0134] As described above, by using the active balun circuit of the present disclosure, the size of the semiconductor chip can be reduced and the symmetry of the differential signal can be satisfied.

Claims

1. An active balun circuit, comprising: A circuit element, directly connected to a reference potential, whose impedance at the fundamental frequency of an input signal becomes an impedance that is 10 times or more of the normalized impedance; a first transistor including a first terminal connected to a reference potential via the circuit element, a second terminal connected to the input terminal, and a third terminal connected to a power supply voltage terminal; and a second transistor including a first terminal connected to the reference potential via the circuit element, a second terminal directly connected to the reference potential, and a third terminal connected to the power supply voltage terminal, outputting a pair of differential signals corresponding to the input signal from the third terminal of the first transistor and the third terminal of the second transistor, The first terminal of the first transistor is an emitter, The second terminal of the first transistor is a base, The third terminal of the first transistor is a collector. The first terminal of the second transistor is an emitter, The second terminal of the second transistor is a base, The third terminal of the second transistor is a collector, The circuit element includes an inductor having one end connected to a connection point between the first terminal of the first transistor and the first terminal of the second transistor and having the other end connected to the reference potential.

2. An active balun circuit, comprising: A circuit element, directly connected to a reference potential, whose impedance at the fundamental frequency of an input signal becomes an impedance that is 10 times or more of the normalized impedance; a first transistor having a first terminal connected to the reference potential via the circuit element, a second terminal connected to the input terminal, and a third terminal connected to the power supply voltage terminal; and a second transistor including a first terminal connected to the reference potential via the circuit element, a second terminal directly connected to the reference potential, and a third terminal connected to the power supply voltage terminal, outputting a pair of differential signals corresponding to the input signal from the third terminal of the first transistor and the third terminal of the second transistor, The first terminal of the first transistor is an emitter, The second terminal of the first transistor is a base, The third terminal of the first transistor is a collector. The first terminal of the second transistor is an emitter, The second terminal of the second transistor is a base, The third terminal of the second transistor is a collector, The circuit elements include: an inductor having one end connected to a connection point between the first terminal of the first transistor and the first terminal of the second transistor and the other end connected to the reference potential; and A capacitor is connected in parallel with the inductor.

3. An active balun circuit, comprising: A circuit element, directly connected to a reference potential, whose impedance at the fundamental frequency of an input signal becomes an impedance that is 10 times or more of the normalized impedance; a first transistor including a first terminal connected to a reference potential via the circuit element, a second terminal connected to the input terminal, and a third terminal connected to a power supply voltage terminal; and a second transistor including a first terminal connected to the reference potential via the circuit element, a second terminal directly connected to the reference potential, and a third terminal connected to the power supply voltage terminal, outputting a pair of differential signals corresponding to the input signal from the third terminal of the first transistor and the third terminal of the second transistor, The first terminal of the first transistor is an emitter, The second terminal of the first transistor is a base, The third terminal of the first transistor is a collector. The first terminal of the second transistor is an emitter, The second terminal of the second transistor is a base, The third terminal of the second transistor is a collector, The circuit element has a wiring having a quarter wavelength of a fundamental frequency of an input signal to the input terminal.

4. A power amplifier circuit, comprising: An active balun circuit as claimed in any one of claims 1 to 3; and A pair of amplifiers takes the pair of differential signals as input.

5. The power amplifier circuit according to claim 4, wherein: The active balun circuit includes a transmission line transformer connected to the transmission paths of the pair of differential signals, respectively. The transmission line transformer performs impedance matching between the first transistor and the second transistor and the pair of amplifiers.

6. A power amplifier module, comprising: A semiconductor chip comprising a portion of the active balun circuit according to any one of claims 1 to 3 except for the circuit elements; a substrate, electrically connected to the semiconductor chip; and A pair of amplifiers, taking the differential signal as input, The substrate has the circuit elements of the active balun circuit.

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