JP4733560B2 - Power amplifier and wireless communication device - Google Patents

Description

  The present invention relates to a power amplifier, in particular, a power amplifier that compensates for temperature characteristics of a power amplifier using a bipolar transistor by using a VBE (base-emitter voltage) dependent voltage source as a base bias circuit, and such a power amplifier. The present invention relates to a communication terminal device using the.

  In recent years, the demand for wireless communication devices typified by mobile phones has been increasing. In such a wireless communication apparatus, the operation of the power amplifier is important.

  As an amplifying element of a power amplifier for amplifying a signal or the like, a bipolar transistor is generally used. The bipolar transistor has a temperature characteristic that when the ambient temperature increases, the on-voltage between the base and the emitter decreases and the collector current increases.

  As a technique for compensating for such temperature characteristics, there is one disclosed in Patent Document 1. In this technique, a temperature compensation circuit using a VBE-dependent voltage source is used for a bias circuit that applies a bias voltage to a power amplifier. The VBE-dependent voltage source is a voltage source having the same temperature characteristics as the on-voltage between the base and emitter of a bipolar transistor that is an amplifying element of a power amplifier. By this temperature compensation circuit, the change of the collector current due to the temperature change is canceled, and the power amplifier is stabilized.

  As another technique for compensating the temperature characteristic, there is a technique disclosed in Patent Document 2. This technique employs a configuration in which the bias circuit is separated from the amplifying element in high frequency by a high frequency choke coil. In general, it is difficult to manufacture a high frequency choke coil on a semiconductor substrate. In order to solve this problem, there is a method using a large spiral inductance. However, this method has a drawback that the spiral inductance occupies a large area on the semiconductor substrate and the manufacturing cost increases. Therefore, Patent Document 2 proposes a method using a resistor instead of the high-frequency choke coil.

  Still another technique for compensating temperature characteristics is disclosed in Patent Document 3. In this technique, a configuration in which transistors are stacked in two stages is adopted as a voltage source circuit.

  Patent Document 4 discloses a configuration in which a current source circuit is used as a power source of a voltage source circuit.

  Patent Document 5 discloses a configuration in which transistors are stacked in two stages, and a bias circuit and an amplifying element are separated in a high frequency by a wire and a spiral inductance. In this configuration, the collector terminal and the base terminal of the transistor are connected, and the transistor is used as a diode.

  Patent Document 6 discloses a structure in which two transistors are combined in another configuration.

  The distortion compensation circuit of the power amplifier using the bipolar transistor used in the above Patent Documents 1 to 5 is based on the technology disclosed in Patent Documents 6 and 7.

  Moreover, the adjustment method of the said distortion compensation circuit is disclosed by patent document 8 and patent document 9. FIG.

  FIG. 1 shows a schematic diagram of a circuit configuration of a general power amplifier 30 according to the prior art. Referring to FIG. 1, power amplifier 30 has an input terminal 40 and an output terminal 52.

  The power amplifier 30 further includes a matching circuit 42, a VBE dependent voltage source 44, a bias terminal 46, a transistor 48, and a matching circuit 50.

  VBE-dependent voltage source 44 includes a bias terminal 60, a resistor 62, a transistor 64, and a resistor 66.

  One terminal of the matching circuit 42 is connected to the input terminal 40. The other terminal of the matching circuit 42 is commonly connected to one end of the resistor 62 included in the VBE-dependent voltage source 44 and the collector terminal and base terminal of the transistor 64. The other end of the resistor 62 is connected to the bias terminal 60.

  The emitter terminal of the transistor 64 is connected to one end of the resistor 66. The other end of the resistor 66 is grounded.

  The base terminal of the transistor 48 is connected to a connection node between the matching circuit 42 and the resistor 62. The emitter terminal of the transistor 48 is grounded.

  Further, the collector terminal of the transistor 48 is connected to the bias terminal 46 and one end of the matching circuit 50 via a connection node. The other end of the matching circuit 50 is connected to the output terminal 52.

  The power amplifier 30 operates as follows. Since the emitter terminal of the transistor 48 is grounded and the bias terminal 46 is connected to the collector terminal, a bias voltage is applied between the collector and emitter of the transistor 48.

  Of the voltage applied from the input terminal 40, only the AC component passes through the matching circuit 42. The passed AC component is applied to the base terminal of the transistor 48. The amplified signal is output from the collector terminal of the transistor 48, and only the AC component is output from the output terminal 52 by the matching circuit 50.

  According to the power amplifier 30, temperature compensation can be performed so that the output voltage of the VBE-dependent voltage source 44 has the same temperature characteristics as the voltage to be applied to the base terminal of the transistor 48 that is an amplifying element. That is, the VBE dependent voltage source 44 functions as a temperature compensation circuit.

  When the temperature increases in the VBE-dependent voltage source 44, the on-voltage between the base and the emitter of the transistor 64 included in the VBE-dependent voltage source 44 decreases. As a result, the bias voltage to the base terminal of the transistor 48 decreases.

Therefore, the influence due to the collector current increase of the transistor 48 accompanying the temperature rise is canceled out. As described above, the base bias voltage can be changed according to the temperature by the VBE-dependent voltage source 44. The fluctuation of the output characteristic of the power amplifier 30 due to the temperature can be suppressed by the fluctuation of the base bias voltage.
Japanese Patent Laid-Open No. 2003-17947 JP 2001-257540 A JP 2003-283274 A JP 2002-335135 A JP 2005-143079 A Japanese Patent Laid-Open No. 2004-80356 JP-A-9-260964 JP 2002-84144 A JP 2001-94360 A

  2. Description of the Related Art In recent years, wireless communication devices used as mobile phones and wireless network devices that are generally used have been required to have power amplifiers with higher wireless transmission performance and higher linearity. High linearity means that the gain variation and phase variation depending on the input signal level are small. There is also a demand for a power amplifier with high output and high linearity.

  However, if the input signal level is increased by using the power amplifier including the conventional temperature compensation circuit as described above, there is a problem that the gain is greatly lowered and the linearity is deteriorated at a certain signal level or higher.

  Therefore, an object of the present invention is to provide a power amplifier that can maintain a high linearity even when the signal level exceeds a certain level.

  Another object of the present invention is to provide a power amplifier that can maintain high linearity even at a certain signal level or higher and can be easily and inexpensively manufactured on an integrated circuit.

  Still another object of the present invention is to provide a wireless communication apparatus having a good linearity using a power amplifier as described above.

  An amplifier according to a first aspect of the present invention is an amplifier having a signal input terminal, a signal output terminal, and a first control terminal, which is connected to a first potential and outputs an output signal to the signal output terminal. A first bipolar transistor having a collector terminal connected to output, an emitter terminal connected to a second potential, and a base terminal connected to receive an input signal from the signal input terminal; A base bias circuit defining a base bias of the first bipolar transistor, wherein the base bias circuit includes a second bipolar transistor having a collector terminal connected to the base terminal of the first bipolar transistor, a third potential, A first resistor connected between the collector terminals of the two bipolar transistors and a collector terminal of the second bipolar transistor The second bipolar transistor is connected between the base terminal of the second bipolar transistor and connected between the low-pass filter having continuity with respect to direct current, the emitter terminal of the second bipolar transistor, and the second potential. Including resistance.

  According to this amplifier, a VBE-dependent voltage source is configured in which the collector terminal of the second bipolar transistor is the voltage output terminal. There is a low-pass filter that is conductive to direct current and connects between the collector terminal of the second bipolar transistor included in the base bias circuit and the base terminal of the second bipolar transistor. Due to the presence of the low-pass filter, even if the fluctuation of the input signal level reaches between the collector terminal and the base terminal of the second bipolar transistor, the magnitude is attenuated. As a result, the base bias circuit is less dependent on the input signal level. As a result, it is possible to provide an amplifier with little gain change up to high output and improved linearity.

  Preferably, the second potential is a ground potential.

  Preferably, the low-pass filter includes a third resistor connected between the collector terminal and the base terminal of the second bipolar transistor, and a capacitive element connected between the second base terminal and the second potential. Including.

  According to this amplifier, the low-pass filter is composed of the third resistor and the capacitive element, so that it is conductive to direct current. The third resistor is connected to the collector terminal side of the second bipolar transistor, that is, the voltage output side, rather than the capacitive element. Therefore, the impedance of the low-pass filter when viewed from the first transistor side appears to be greater than or equal to the resistance value of the third resistor. That is, the impedance matching of the base terminal of the first transistor is hardly affected. As a result, it is possible to provide an amplifier with little gain change up to high output and improved linearity.

  More preferably, the amplifier further includes a matching circuit connected between the signal input terminal and the base terminal.

  More preferably, the amplifier further includes a distortion compensation circuit connected between a connection point between the first resistor of the base bias circuit and the second bipolar transistor and a base terminal of the first bipolar transistor.

  According to this amplifier, a distortion compensation circuit is incorporated. Therefore, the linearity can be improved by suppressing a temporary increase in gain. As a result, an amplifier with improved linearity can be provided.

  More preferably, the amplifier further includes a third bipolar transistor having a collector terminal and a base terminal connected to the emitter terminal of the second bipolar transistor, and an emitter terminal connected to the second resistor.

  According to this amplifier, the voltage of the base bias circuit is defined by the base-emitter voltage of the second bipolar transistor and the third bipolar transistor. An appropriate voltage considering the voltage effect in the distortion compensation circuit can be supplied to the first bipolar transistor, and as a result, an amplifier capable of efficiently amplifying an electric signal can be provided.

  Preferably, the distortion compensation circuit includes a collector terminal connected to the fourth potential, a base terminal connected to a connection point between the first resistor and the collector terminal of the second bipolar transistor, and the first bipolar transistor. A fourth bipolar transistor having an emitter terminal connected to the base terminal; and an impedance element connected to the base terminal of the fourth bipolar transistor and a fourth potential.

  According to this amplifier, the distortion compensation circuit includes an impedance element. Therefore, this impedance element is an element for adjusting the distortion compensation circuit. As a result, an amplifier capable of efficiently compensating for distortion can be provided.

  Preferably, the connection path between the collector terminal and the base terminal of the second bipolar transistor is only a low-pass filter.

  According to this amplifier, the collector terminal and the base terminal of the second bipolar transistor are connected only by the low-pass filter. Therefore, an AC signal is not applied to the base terminal of the second transistor without the signal being attenuated by the low-pass filter. As a result, an amplifier with improved linearity can be provided.

  An amplifier according to a second aspect of the present invention is an amplifier having a signal input terminal, a signal output terminal, and a first control terminal, which is connected to a first potential and outputs an output signal to the signal output terminal. A first bipolar transistor having a collector terminal connected to output, an emitter terminal connected to a second potential, and a base terminal connected to receive an input signal from the signal input terminal; A base bias circuit for defining a base bias of the bipolar transistor, and a distortion compensation circuit connected between the base bias circuit and the base terminal of the first bipolar transistor, wherein the base bias circuit is one end of the distortion compensation circuit. And a second bipolar transistor having a collector terminal connected to the third potential and between the third potential and the collector terminal of the second bipolar transistor. A third bipolar transistor having a first resistor connected, a collector terminal connected to a fourth potential, and an emitter terminal connected to a base terminal of the second bipolar transistor; and a second bipolar transistor Connected between the collector terminal of the first bipolar transistor and the base terminal of the third bipolar transistor, and is connected between the low-pass filter that is conductive to direct current, the emitter terminal of the second bipolar transistor, and the second potential. A second resistor.

  According to this amplifier, there is a low-pass filter that is conductive to direct current and that connects between the collector terminal of the second bipolar transistor and the base terminal of the third bipolar transistor. Due to the presence of the low-pass filter, the fluctuation in the level of the base-emitter voltage of the second bipolar transistor due to the input AC signal is attenuated, and the base bias circuit becomes less dependent on the input signal level. As a result, it is possible to provide an amplifier with little gain change up to high output and improved linearity.

  Preferably, the low pass filter includes a resistor connected between the collector terminal of the second bipolar transistor and the base terminal of the third bipolar transistor, and between the base terminal of the third bipolar transistor and the second potential. And a capacitor element connected to the capacitor.

  According to this amplifier, the low-pass filter is constituted by a resistor and a capacitive element connected between the base terminal of the third bipolar transistor, so that it is conductive to direct current. The resistor is connected to the collector terminal side of the second bipolar transistor, that is, the voltage output side, rather than the capacitor element. Therefore, the impedance of the low-pass filter when viewed from the first transistor side appears to be greater than the resistance value of the resistor. That is, the impedance matching of the base terminal of the first transistor is hardly affected. As a result, it is possible to provide an amplifier with little gain change up to high output and improved linearity.

  Preferably, the distortion compensation circuit includes a collector terminal connected to the fifth potential, an emitter terminal connected to the base terminal of the first bipolar transistor, and a base terminal connected to the collector terminal of the second bipolar transistor. A fourth bipolar transistor, and an impedance element connected between the base terminal of the fourth bipolar transistor and the second potential.

  According to this amplifier, the distortion compensation circuit includes an impedance element. Therefore, this impedance element is an element for adjusting the distortion compensation circuit. As a result, an amplifier capable of efficiently compensating for distortion can be provided.

  Preferably, the impedance element includes a variable impedance circuit that changes the impedance according to a control signal given from the outside.

  According to this amplifier, the impedance can be changed according to a control signal given from the outside. Therefore, the distortion compensation circuit can be operated with the optimum impedance value. As a result, an amplifier capable of efficiently compensating for distortion can be provided.

  Preferably, the variable impedance circuit includes a capacitor having a first terminal connected to a base terminal of the fourth bipolar transistor, a source terminal connected to the second terminal of the capacitor of the variable impedance circuit, and a second terminal. And a field effect transistor having a drain terminal connected to the potential and a gate terminal connected to receive a control signal.

  According to this amplifier, the impedance of the impedance element can be changed by changing the gate voltage of the field effect transistor. Therefore, the distortion compensation circuit can be operated with the optimum impedance value. As a result, an amplifier capable of efficiently compensating for distortion can be provided.

  The field effect transistor may include a metal-oxide semiconductor field-effect transistor (MOSFET).

  A wireless communication apparatus according to a third aspect of the present invention includes any of the amplifiers described above.

  According to this wireless device, a wireless communication device with good linearity can be provided by using a power amplifier that can maintain high linearity.

  A wireless communication apparatus according to a fourth aspect of the present invention includes any one of the amplifiers described above, and means for providing a control signal to the amplifier according to the operating state of the amplifier.

  According to the present invention, it is possible to provide an amplifier with little gain change up to high output and improved linearity.

  Further, since the magnitude of the voltage can be easily changed by the amplifying element, it is possible to provide an amplifier capable of efficiently amplifying the electric signal.

  Furthermore, it is possible to provide an amplifier capable of efficiently compensating for distortion and a wireless communication apparatus with good linearity.

  Furthermore, since it is not necessary to use an element that occupies a large area, an integrated circuit can be easily formed at low cost.

[First Embodiment]
<Configuration>
FIG. 2 is a circuit diagram showing the configuration of the power amplifier 70 according to the first embodiment of the present invention. Referring to FIG. 2, power amplifier 70 has a signal input terminal 80, a signal output terminal 92, a collector bias terminal 86, and a bias terminal 100.

  The power amplifier 70 includes a matching circuit 82 having one terminal connected to the signal input terminal 80, a VBE-dependent voltage source 84 having one terminal connected to the other terminal of the matching circuit 82, and a VBE-dependent voltage source 84. The transistor 88 has a base terminal connected to the other terminal, a collector terminal connected to the collector bias terminal 86, a matching terminal connected to the collector terminal of the transistor 88, and the other terminal connected to the signal output terminal 92. Circuit 90.

  The VBE-dependent voltage source 84 includes a resistor 102 having one end connected to the bias terminal 100 and the other end connected to the base terminal of the transistor 88, and a collector terminal connected to the matching circuit 82 and the base terminal of the transistor 88. , A low-pass filter 108 connected between the collector terminal and the base terminal of the transistor 104, and a resistor 106 having one terminal connected to the emitter terminal of the transistor 104 and the other terminal grounded.

  The low-pass filter 108 has one terminal connected to the emitter terminal of the transistor 104, the other terminal connected to the base terminal of the transistor 104, one terminal connected to the base terminal of the transistor 104, and the other terminal grounded. Capacity 110 is included. The low-pass filter 108 is conductive to direct current.

  The transistor 104 of the VBE-dependent voltage source 84 is a transistor that defines a voltage applied to the base terminal of the transistor 88 by the base-emitter voltage. The collector terminal of the transistor 104 is a voltage output terminal.

  The element values of the resistor 112 and the capacitor 110 constituting the low-pass filter 108 need to be designed as a filter that can cut off the applied AC signal as much as necessary. This can be designed with known techniques in low pass filter design. For example, the cutoff frequency of the filter may be designed to be sufficiently smaller than the operating frequency. Alternatively, the value of the resistor 112 is increased, and the transmission loss of the filter is designed to be large.

  The element used in the low-pass filter 108 according to the present embodiment needs to be configured by a linear element whose impedance value does not change with respect to a change in the AC signal level. Otherwise, the impedance changes as the AC signal level increases, causing the DC voltage output of the VBE-dependent voltage source 84 to fluctuate.

  Further, in a configuration in which another circuit is connected in parallel with the low-pass filter 108 and the AC signal reaches the base terminal of the transistor 104, the effect of reducing the input signal level dependency of the present invention does not occur.

  Furthermore, the positions of the capacitor 110 and the resistor 112 of the low-pass filter 108 are also important. Since the resistor 112 is on the collector side of the transistor 104, the impedance of the VBE-dependent voltage source 84 seen from the base terminal of the transistor 88 appears large. Therefore, when the low-pass filter 108 is used as a bias circuit, there is an advantage that impedance matching of the base terminal of the transistor 88 is hardly affected.

  The reason why the impedance looks large is that the resistor 112 is arranged on the output side of the VBE-dependent voltage source as a series resistor. With this arrangement, the impedance of the filter viewed from the base terminal of the transistor 88 appears to be greater than or equal to the resistance value of the resistor 112.

  The collector terminal of the transistor 104 is also connected to the base terminal of the transistor 88. Transistor 88 acts as a current source whose collector current depends on the base-emitter voltage of the transistor. In the transistor 104, since the low-pass filter 108 is connected to the collector terminal and the base terminal, the AC signal is attenuated and applied to the base terminal, and the impedance of the collector terminal looks large.

  Due to these properties, the VBE-dependent voltage source 84 of the power amplifier 70 according to the present embodiment has high output impedance with respect to AC. From the above, it can be said that even in the same low-pass filter, a low-pass filter having a series resistance on the output side of the VBE-dependent voltage source is the most effective configuration.

  Other methods are also conceivable as long as the input signal level dependency of the voltage output of the VBE-dependent voltage source is reduced. As an example, there is a method in which a plurality of impedances are included in the VBE-dependent voltage source and any one of the impedance values is increased.

  For example, the resistance value is increased by using an impedance element connected to the emitter terminal of a transistor included in the VBE-dependent voltage source as a resistance element. However, in this case, since the emitter current of the transistor flows in the impedance element, a large voltage drop occurs, which greatly affects the voltage output of the VBE-dependent voltage. Examples of the influence include deterioration of voltage characteristics. Therefore, it is inappropriate as a means for reducing the dependency of the voltage output of the VBE-dependent voltage source on the input signal level.

  This is the same even when the resistance value is increased by using the impedance element connected to the collector terminal of the transistor as a resistance element. A transistor collector current flows through this impedance. Therefore, a large voltage drop occurs, and the voltage output of the VBE-dependent voltage source is greatly affected as in the case of the impedance element.

<Operation>
Referring to FIG. 2, power amplifier 70 operates as follows. An AC signal is applied to the power amplifier 70 through the signal input terminal 80. The applied AC signal is applied to the base terminal of the transistor 88 via the matching circuit 82, and the amplified AC signal is output from the collector terminal of the transistor 88. The amplified AC signal is output from the output terminal 92 via the matching circuit 90.

  Next, the operation of the VBE-dependent voltage source 84 according to this embodiment as a voltage source circuit will be described.

  The relationship between the base current Ib and the collector current Ic of the transistor 104 can be expressed by the following equation (1).

Ib = Ic ÷ β (1)
Here, β is a current amplification factor of the transistor 104 and takes a value of about 100, for example.

  The voltage drop Vfilter due to the low-pass filter 108 can be expressed by Expression (2).

Vfilter = R1 × Ib (2)
Here, R1 is the resistance value of the resistor 112, which is a series resistor included in the low-pass filter 108. The voltage drop Vfilter due to the low-pass filter 108 has a relatively small value because β takes a large value. As a result, the collector voltage and the base voltage of the transistor 104 have substantially the same value.

  If the collector voltage and the base voltage of the transistor 104 are substantially the same value, the VBE-dependent voltage source 84 is connected to the collector voltage of the transistor 104 in the same manner as the conventional VBE-dependent voltage source 44 shown in FIG. Depending on the constituent material, a voltage having a substantially constant value is supplied.

  At this time, the collector voltage Vc of the transistor 104 is expressed by the following equation (3).

Vc = Vfilter + Von + Ic × (1 + 1 ÷ β) × R2 (3)
Here, Von is a base-emitter on-voltage determined by the constituent material of the transistor 104. The on-voltage is a voltage at which a current starts to flow between the collector and the emitter of the transistor 104. Ic × (1 + 1 ÷ β) is an emitter current. Therefore, Ic × (1 + 1 ÷ β) × R2 corresponds to a voltage drop due to the resistor 106. Here, R2 is a resistance value of the resistor 106, and is generally a relatively small resistance value added for adjusting the temperature characteristics.

  For the above-described operation, the low-pass filter 108 in the present embodiment needs to have a transfer characteristic having direct current conduction.

  Next, temperature compensation characteristics of the power amplifier when the VBE-dependent voltage source 84 according to the present embodiment is used as a bias circuit will be described.

  As described above, the collector voltage of the transistor 104, which is the output power of the VBE-dependent voltage source 84, depends on the on-voltage Von as shown in the equation (3), and the temperature dependence reflects the temperature dependence of Von. Have sex. The role played by this temperature dependence will be described below.

  The transistor 88 which is an amplifying element has a temperature characteristic that when the ambient temperature increases, the on-voltage between the base and the emitter decreases and the collector current increases. However, at that time, the on-voltage Von between the base and emitter of the transistor 104 included in the VBE-dependent voltage source 84 also decreases. As the ON voltage Von decreases, the output voltage of the VBE-dependent voltage source 84 also decreases. That is, the base bias voltage of the transistor 88 is lowered, thereby canceling the action of increasing the collector current of the transistor 88. Accordingly, the temperature dependency of the collector current characteristic reflecting the temperature dependency of the ON voltage between the base and the emitter of the transistor 88 is also canceled out.

<Comparison of results>
FIG. 3 is a graph showing a comparison between a temperature-dependent circuit simulation when temperature compensation is performed and a temperature-dependent circuit simulation when temperature compensation is not performed. A graph 120 shows the circuit simulation result of the temperature dependence when the base voltage of the transistor is constant at 0.81 V and temperature compensation is not performed. A graph 122 shows the circuit simulation result of the temperature dependence of the collector current of the transistor 88 having the configuration shown in FIG.

  Here, a model of a SiGe bipolar transistor having an ON voltage of about 0.8 V was used as the transistor 88.

  The calculation was performed assuming that the resistance value of the resistor 102 is 2400Ω, the resistance value of the resistor 106 is 20Ω, the resistance value of the resistor 112 is 1000Ω, and the capacitance 110 is 3 pF. In addition, the matching circuit 82 and the matching circuit 90 are configured not to conduct with respect to the direct current so that the direct current bias does not pass therethrough. A voltage of 2.9 V was applied to the bias terminal 100 and a voltage of 3.3 V was applied to the collector bias terminal 86.

  As shown in FIG. 3, the collector current increased when the temperature compensation represented by the graph 120 was not performed as the temperature increased. On the other hand, in the configuration of the present embodiment represented by the graph 122, the collector current hardly changed even when the temperature increased.

  Since the low-pass filter 108 has a series resistance 112 (1000Ω), there is a difference in characteristics that cannot be distinguished from the scale of the graph of FIG. 3 between the configuration of the conventional technique and the configuration of the present embodiment. However, this can be easily adjusted with a slight change in the adjusting resistor 106. For example, in order to match the characteristics when the resistance 66 is set to 30Ω in the prior art (FIG. 1), the resistance 106 may be set to 20Ω in the configuration of the present embodiment shown in FIG.

  In general, the temperature compensation of the power amplifier 70 is adjusted so that the collector current of the transistor 88 is approximately constant, thereby making the gain of the power amplifier 70 approximately constant. In practice, the temperature compensation may be adjusted so that the collector current has a moderate temperature dependence according to the specifications of the entire circuit. The resistor 102 and the resistor 106 can finely adjust the temperature dependence and finely adjust the absolute value of the collector current.

  Next, input signal level dependency when the VBE-dependent voltage source 84 of the present invention is used as a bias circuit will be described.

  When an AC signal is applied from the input signal terminal 80, the input AC signal is applied not only to the base terminal of the transistor 88 but also to the VBE-dependent voltage source 84. When the signal level of the AC input increases, the impedances of the resistors 102, 106, and 112 and the capacitor 110 are linear elements that do not change regardless of the signal level. On the other hand, since the transistor 104 is a non-linear element, the impedance changes as the signal level increases, causing changes in the voltage and current components.

  Specifically, when the level of the AC signal reaching between the base and emitter of the transistor 104 increases, the DC component of the collector current of the transistor 104 increases. As a result, the voltage drop due to the resistor 102 increases, and the DC component of the collector voltage of the transistor 104 decreases. Then, the bias condition of the transistor 88 is affected.

  However, according to the configuration according to the present embodiment in FIG. 2, the input AC signal reaches the base terminal via the low-pass filter 108. That is, the level of the AC signal is attenuated by the low-pass filter 108. Therefore, for the same input signal level, the AC signal level applied to the base terminal is reduced, and the dependency of the voltage output of the VBE-dependent voltage source 84 on the input signal level is reduced. That is, the input signal level dependency of the DC voltage output of the VBE-dependent voltage source 84 is reduced.

  Hereinafter, the voltage output of the voltage source circuit in the present invention means a DC voltage output.

  FIG. 4 is a graph 130 showing the circuit simulation result of the input signal level dependency which is the relationship between the collector voltage of the transistor 88, which is the output voltage of the power amplifier 70 according to the present embodiment, and the input signal power. A graph 132 shows the results of circuit simulation of the dependency of the collector voltage on the input signal level in the circuit configuration according to the prior art (see FIG. 1). The circuit parameters and bias conditions used were the same as when the above temperature characteristics were calculated.

  Referring to FIG. 4, for example, the input signal level when the collector voltage of transistor 88 is reduced to 0.7 V is about 7 dBm as shown in graph 132 in the circuit configuration according to the prior art. On the other hand, in the circuit configuration of the present embodiment, as shown in the graph 130, it was about 15 dBm. From the above, it can be said that, according to the power amplifier 70 according to the present embodiment, the dependency on the input signal level is reduced as compared with the conventional one.

  FIG. 5 shows the relationship between the gain of the power amplifier and the input signal power in the case similar to the above by graphs 140 and 142 for the present embodiment and the prior art of FIG. Referring to FIG. 5, for example, the input signal level when the gain is reduced to 6 dB is 5 dBm as shown by the graph 142 in the circuit configuration according to the related art. On the other hand, in the circuit configuration of the present embodiment, as indicated by the graph 140, it was 7.5 dBm. From the above, it can be said that in the power amplifier 70 according to the present embodiment, the gain change is small up to a high output and the linearity is improved as compared with the prior art.

  The power amplifier 70 according to the present embodiment can be manufactured without occupying a large area in an integrated circuit on a semiconductor substrate. Therefore, a power amplifier with high linearity can be provided inexpensively and easily.

  Instead of connecting the emitter terminal of the transistor 104 to the ground terminal via the resistor 106 as shown in FIG. 2, the resistor 106 may be omitted and the emitter terminal of the transistor 104 may be directly connected to the ground terminal.

  Further, a current source circuit may be used instead of the resistor 102 and the bias terminal 100 as in the conventional temperature compensation circuit.

If only the input signal level dependency of the voltage output of the VBE-dependent voltage source is reduced,
For example, an inductance element may be provided between the connection node of the base terminal of the transistor 48 and the resistor 62 shown in FIG. 1 and the collector terminal of the transistor 64 to increase the inductance value. However, in order to sufficiently attenuate the AC signal, a large inductance is required. If the inductance element is manufactured on a semiconductor substrate with a spiral inductor or the like, the element area becomes large. Therefore, there is a drawback that the cost of the integrated circuit is greatly increased. In addition to this, a method using a large inductance is conceivable, but all occupy a large area on the semiconductor substrate, which is not preferable.

  On the other hand, in the structure of this embodiment mode, the integrated circuit on the semiconductor substrate can be manufactured without occupying a large area. Therefore, it is possible to provide an inexpensive communication device that can perform stable communication with few communication errors by using a communication device using the power amplifier with high linearity.

[Second Embodiment]
<Configuration>
FIG. 6 is a circuit diagram showing a configuration of a power amplifier 148 according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the element same as the element contained in the amplifier which concerns on 1st Embodiment. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 6, power amplifier 148 has a signal input terminal 80, a signal output terminal 92, and a collector bias terminal 86.

  The power amplifier 148 includes a matching circuit 82 having a first terminal connected to the signal input terminal 80, a base terminal connected to the second terminal of the matching circuit 82, a collector terminal connected to the collector bias terminal 86, A transistor 88 having an emitter terminal grounded, and a matching circuit 90 connected between the collector terminal of the transistor 88 and the signal output terminal 92 are included.

  The power amplifier 148 further includes a first terminal connected to a connection node between the second terminal of the matching circuit 82 and the base terminal of the transistor 88, a second terminal, and a bias terminal 170. And a VBE-dependent voltage source 150 connected to the second terminal of the distortion compensation circuit 152.

  The VBE dependent voltage source 150 has a bias terminal 100. The VBE-dependent voltage source 150 includes a resistor 102 having one terminal connected to the bias terminal 100 and the other terminal connected to the second terminal of the distortion compensation circuit 152, and the resistor 102 and the distortion compensation circuit 152. A transistor 160 having a collector terminal connected to the connection node, a low-pass filter 108 connected between the collector terminal and the base terminal of the transistor 160, and a collector terminal and a base terminal connected to the emitter terminal of the transistor 160 Transistor 162 and resistor 106 connected between the emitter terminal of transistor 162 and ground are included.

  The low-pass filter 108 includes a resistor 112 and a capacitor 110 similar to those according to the first embodiment.

  The distortion compensation circuit 152 includes a collector terminal connected to the bias terminal 170, a base terminal connected to a connection node between the first resistor 102 of the VBE-dependent voltage source 150 and the collector terminal of the transistor 160, and a matching circuit 82. Transistor 172 having an emitter terminal connected to a connection node with the base terminal of transistor 88, and impedance element 174 connected between the base terminal of transistor 172 and ground.

  Here, the transistor 160 and the transistor 162 are transistors that define a voltage applied to the base terminal of the transistor 88 by a base-emitter voltage. The collector terminal of the transistor 160 is a voltage output terminal.

  The basic configuration of the distortion compensation circuit 152 is shown in Patent Document 7. In particular, Patent Document 8 and Patent Document 9 describe a method for adjusting the distortion compensation circuit. The impedance element 174 in the present embodiment corresponds to the adjustment element.

  Examples in which these circuits are combined with a voltage source circuit for temperature compensation are described in Patent Document 4 and Patent Document 6.

  Further, as in the first embodiment, the following can be said.

  First, the low-pass filter 108 needs to be designed as a filter that can cut off the applied AC signal as much as necessary. Further, the element used in the low-pass filter 108 needs to be composed of a linear element whose impedance value does not change with respect to the change of the AC signal level.

  Furthermore, in the configuration in which another circuit is connected in parallel with the low-pass filter 108 and the AC signal reaches the base of the transistor 88, the effect of reducing the input signal level dependency of the present invention does not occur. Further, in order for the VBE-dependent voltage source 150 to function as a voltage source circuit, it is necessary that the low-pass filter 108 is conductive to direct current.

  Furthermore, the positions of the capacitor 110 and the resistor 112 of the low-pass filter 108 are also important. Since the resistor 112 is on the output terminal side of the VBE-dependent voltage source 150, the impedance of the VBE-dependent voltage source 150 viewed from the base terminal of the transistor 172 appears large. The reason why the impedance looks large is the same as in the first embodiment.

  In this embodiment, since the output terminal of the VBE-dependent voltage source 150 is not directly connected to the base terminal of the transistor 88, the influence on the impedance matching of the transistor 88 is small. However, it is necessary to pay attention to the influence of the power amplifier on the distortion compensation circuit 152.

  By changing the impedance value of the impedance element 174, the linearity is adjusted as described later in <Result comparison>. A VBE-dependent voltage source 150 is connected to the base terminal of the transistor 172 in parallel with the impedance circuit 174. Therefore, when the impedance of the VBE-dependent voltage source 150 is small, the impedance viewed from the base terminal of the transistor 172 does not become larger than the impedance of the VBE-dependent voltage source 150 even if the impedance of the impedance circuit 174 is increased. As a result, the adjustment range of the distortion compensation circuit 152 is narrowed.

  However, in the configuration of the present invention, the resistor 112 is on the output terminal side of the VBE dependent voltage source 150. Therefore, the impedance of the VBE-dependent voltage source 150 viewed from the base terminal of the transistor 88 is increased, and there is an advantage that the adjustment range of the distortion compensation circuit 152 is not narrowed. This is particularly effective when the impedance element 174 is a variable impedance circuit in the configuration described in the fourth embodiment to be described later, and the distortion compensation circuit is adjusted according to the operating state, and the adjustment range is wide. It has the advantage of being able to.

  Thus, even with the same low-pass filter, a low-pass filter having a series resistance on the output side of the VBE-dependent voltage source 150 is the most effective configuration for the present invention.

<Operation>
The basic operation of the power amplifier 148 according to the present embodiment is the same as that of the power amplifier 70 according to the first embodiment. Therefore, detailed description thereof will not be repeated here. However, the operation of the VBE-dependent voltage source 150 included in the power amplifier 148 according to the present embodiment is different from that of the first embodiment, and this point will be described below.

  Referring to FIG. 6, an AC signal is input from signal input terminal 80. The input AC signal is applied to the collector terminal of the transistor 160 that is the output terminal of the VBE-dependent voltage source 150 through the matching circuit 82 and the transistor 172.

  Here, as in the case of the power amplifier 70 according to the first embodiment, the applied AC signal reaches between the base and emitter terminals of the transistor 160. As a result, the collector current of the transistor 160 increases as the input signal level increases. As a result, a voltage drop due to the resistor 102 occurs, and the output voltage of the VBE-dependent voltage source 150 expressed as the collector voltage of the transistor 160 decreases.

  However, in the VBE-dependent power supply 150 according to the present embodiment, the AC signal reaches the base terminal of the transistor 160 after being attenuated by the low-pass filter 108. Therefore, the dependency of the voltage output of the VBE-dependent voltage source 150 on the input signal level is reduced.

<Comparison of results>
7 shows the relationship between the output voltage of the transistor 160 included in the power amplifier 148 and the input signal included in the power amplifier 148 according to the second embodiment, and the voltage without the low-pass filter 108 shown in FIG. The relationship between the output voltage of the transistor 160 and the input signal power when replaced by the source circuit is shown.

  The values used in the circuit simulation are as follows. The resistance value of the resistor 102 was 12530Ω, and the resistance value of the resistor 106 was 480Ω. Further, the resistance value of the resistor 112 was 1000Ω, and the value of the capacitor 110 was 3 pF. The transistor used was a multi-unit SiGe bipolar transistor with a built-in base ballast resistor (equivalent to 16Ω). The capacitance of the impedance element 174 was 0.3 pF. A voltage of 2.9 V was applied to the bias terminal 100 and 3 V was applied to the collector bias terminal 86.

  FIG. 11 shows a voltage source circuit without the low-pass filter 108. In FIG. 11, the same elements as those shown in FIG. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated here. Referring to FIG. 11, this circuit has a terminal 220 connected to a connection node between the first resistor 102 and the collector terminal of the second transistor 160. Terminal 220 is connected to the base terminal of transistor 172 shown in FIG.

  A graph 180 shows the relationship between the output voltage of the collector voltage of the transistor 160 included in the power amplifier 148 according to the present embodiment and the input signal power. A graph 182 shows the relationship between the output voltage of the collector voltage of the transistor 160 included in the circuit shown in FIG. 11 and the input signal power.

  8 is a graph 190 showing the relationship between the base voltage of the transistor 88 included in the power amplifier 148 according to the present embodiment and the input signal power, and the VBE-dependent voltage source 150 of FIG. 6 is shown in FIG. A graph 192 shows the relationship between the base voltage of the transistor 88 and the input signal power when it is replaced by a voltage source circuit having no voltage.

  Referring to FIG. 7, the transistor 160 according to the present embodiment represented by a graph 180 has a voltage source circuit up to an input signal level higher than that of the transistor 160 included in the voltage source circuit of FIG. There was little fluctuation in the output voltage. As a result, as shown in FIG. 8, the decrease in the base voltage of the transistor 88 included in the power amplifier 148 according to the present embodiment represented by the graph 190 is the voltage of FIG. 11 represented by the graph 192. It can be seen that the input signal level is higher than that of the transistor 88 included in the source circuit.

  FIG. 9 is a graph 200 showing the relationship between the gain and the input signal power when the capacitance of the impedance element 174 included in the power amplifier 148 according to the present embodiment is 0.3 pF, and the relationship when the capacitance is 0.1 pF. Is shown by a graph 202.

  FIG. 10 is a graph 210 showing the relationship between the gain and the input signal power when the capacitance of the impedance element 174 included in the power amplifier using the voltage source circuit of FIG. 11 is 0.3 pF, and 0.1 pF. The relationship is shown by a graph 212.

  With reference to FIG. 9 and FIG. 10, for example, attention is paid to a portion where the input signal power in which the base voltage is greatly different in FIG. 8 is 20 dBm. In the graph 200, the gain was about 9.3 dB at this time. On the other hand, in the graph 212, the gain decreased to about 8.6 dB. From the above, it can be seen that the power amplifier 148 according to the present embodiment has little decrease in gain and excellent linearity.

  However, in the configuration replaced with the voltage source circuit of FIG. 11 (graph 210), when the capacitance is reduced, the gain decrease at a high input level is rapidly accelerated as shown in the graph 212. As a result, the linearity is reduced. That is, in the conventional configuration in which the distortion compensation circuit and the voltage source circuit for temperature compensation are simply combined, the assumed distortion compensation effect may not be obtained at a high input signal level as in the graph 212.

  The inventors of the present invention can solve the above problems by using a base-emitter voltage type voltage source circuit having the configuration of the present invention, and can provide an amplifier having more linearity. Then, it has been found that a power amplifier circuit having high linearity using such a base-emitter voltage type voltage source circuit can be constructed.

  As a result of the examination, it has been found that the sharp decrease in gain at a high input level in the graph 212 is also caused by the input signal level dependency of the voltage source circuit. When the impedance of the impedance element 174 decreases, a large AC signal voltage is applied to the output terminal of the VBE-dependent voltage source 150. This application causes a decrease in the output voltage, resulting in a decrease in the base voltage of transistor 88 and a decrease in gain.

  Further, the low-pass filter 108 between the base terminal and the collector terminal of the transistor 160 that defines the base-emitter voltage of the VBE-dependent voltage source 150 in FIG. 6 is omitted, the collector-base terminal is short-circuited, instead, A configuration in which a low-pass filter is connected between the collector and base of the transistor 162 can also be employed.

  In the case of a circuit in which the terminal of the circuit described above is connected to the base of the transistor 172 instead of the VBE-dependent voltage source 150 of FIG. 6, the dependency of the input signal level as the voltage source circuit is not so small. There is almost no effect of improving the linearity when used for. This circuit is considered to be less effective because an AC signal is applied to the base terminal of the transistor 160 before the signal is attenuated by the low-pass filter. That is, when there are a plurality of transistors constituting the voltage source circuit, it is necessary to connect the low pass filter 108 to the base terminal connected to the output terminal of the voltage source circuit as shown in FIG.

  According to the configuration of the present embodiment, a power amplifier with high linearity can be provided.

  Further, as in the first embodiment, since it is not necessary to use an element that occupies a large area, an integrated circuit can be easily formed at low cost.

[Third Embodiment]
<Configuration>
FIG. 12 is a circuit diagram showing a configuration of a power amplifier 228 according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the element same as the element contained in the amplifier which concerns on 1st Embodiment and 2nd Embodiment. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated here.

  Referring to FIG. 12, power amplifier 228 is different from power amplifier 148 according to the second embodiment in that, instead of VBE-dependent voltage source 150 in the second embodiment, bias terminal 100 and bias A VBE dependent voltage source 230 having a terminal 240. In other respects, power amplifier 228 is identical to power amplifier 148.

  The VBE-dependent voltage source 230 includes a resistor 102 having one end connected to the bias terminal 100, a transistor 242 having a collector terminal connected to the other end of the resistor 102, and an emitter terminal of the transistor 242 and ground. , A transistor 244 having a collector terminal connected to the bias terminal 240, and an emitter terminal connected to the base terminal of the transistor 242, and between the collector terminal of the transistor 242 and the base terminal of the transistor 244 And a low-pass filter 108 connected to.

  The internal configuration of the low-pass filter 108 is the same as that described in the first and second embodiments.

  Here, the transistor 242 and the transistor 244 are transistors that define a voltage applied to the base terminal of the transistor 88 by a base-emitter voltage.

  The collector terminal of the transistor 242 becomes a voltage output terminal.

  Further, what is described below is the same as in the case of the first embodiment.

  First, the low-pass filter 108 is designed as a filter that can cut off the applied AC signal as much as necessary, and the elements used in the low-pass filter 108 are composed of linear elements whose impedance value does not change with changes in the AC signal level. It is necessary to be.

  Furthermore, in the configuration in which another circuit is connected in parallel with the low-pass filter 108 and the AC signal reaches the base of the transistor 88, the effect of reducing the input signal level dependency of the present invention does not occur. Further, in order for the VBE-dependent voltage source 230 to function as a voltage source circuit, it is necessary that the low-pass filter 108 is conductive to direct current.

  The positions of the capacitor 110 and the resistor 112 of the low pass filter are also important. Since the resistor 112 is on the output terminal side of the VBE dependent voltage source 230, the impedance of the VBE dependent voltage source 230 seen from the base terminal of the transistor 172 appears large. The reason why the impedance looks large is the same as in the first embodiment. In the power amplifier 228 according to the present embodiment, the output terminal of the VBE dependent voltage source 230 is not directly connected to the base terminal of the transistor 88. Therefore, the influence on the impedance matching of the transistor 88 is small.

  However, it is necessary to pay attention to the influence of the power amplifier on the distortion compensation circuit 152. By changing the impedance value of the impedance element 174, the linearity is adjusted as will be described later in <Result comparison>.

  A VBE-dependent voltage source 230 is connected to the base terminal of the transistor 172 in parallel with the impedance circuit 174. Therefore, when the impedance of the VBE-dependent voltage source 230 is small, even if the impedance of the impedance element 174 is increased, the impedance viewed from the base terminal of the transistor 172 does not become larger than the impedance of the VBE-dependent voltage source 230. As a result, the adjustment range of the distortion compensation circuit 152 is narrowed.

  However, in the configuration of the present invention, since the resistor 112 is on the output terminal side of the VBE dependent voltage source 230, the impedance of the VBE dependent voltage source 230 viewed from the base terminal of the transistor 88 is greatly increased. This has the advantage of not narrowing the adjustment range.

  This is particularly effective when the impedance element 174 is a variable impedance circuit and the distortion compensation circuit is adjusted according to the operating state in the configuration described in the fourth embodiment to be described later. Has the advantage of being broad.

  Thus, even with the same low-pass filter, it can be said that a low-pass filter having a series resistance on the output side of the VBE-dependent voltage source 230 is the most effective configuration for the present invention.

<Operation>
The basic operation of the power amplifier 228 according to the present embodiment is the same as that of the power amplifier 70 according to the first embodiment and the power amplifier 148 according to the second embodiment. Therefore, detailed description of power amplifier 228 will not be repeated here. However, the operation of the VBE-dependent voltage source 230 included in the power amplifier 228 according to this embodiment is different from that of the first embodiment and that of the second embodiment, and this will be described below. To do.

  Referring to FIG. 12, the AC signal input from input terminal 80 is applied to the collector terminal of transistor 242 that is the output terminal of VBE-dependent voltage source 230 via matching circuit 82 and transistor 172. When the applied AC signal reaches between the base and emitter terminals of the transistor 244, the collector current of the transistor 242 increases as the input signal level increases. When the collector current of the transistor 242 increases, the voltage drop due to the resistor 102 increases and the collector voltage of the transistor 242 decreases. However, since the AC signal is attenuated by the low-pass filter 108 and reaches the base terminal of the transistor 244, the fluctuation in the signal level of the base terminal of the transistor 244 is reduced. As a result, the voltage output of the VBE-dependent voltage source 230 is reduced. Input signal level dependency is reduced.

<Comparison of results>
FIG. 13 shows the relationship between the output voltage of the transistor 242 included in the power amplifier 228 and the input signal power included in the power amplifier 228 according to this embodiment, and the VBE-dependent voltage source 230 shown in FIG. 17 shows the relationship between the output voltage of the transistor 242 and the input signal power.

  FIG. 17 shows a voltage source circuit without the low-pass filter 108. In FIG. 17, the same elements as those shown in FIG. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated here. A terminal 290 illustrated in FIG. 17 is connected to a connection node between the first resistor 102 and the second transistor 244, and is connected to the connection node illustrated in FIG.

  The values used in the circuit simulation whose results are shown in FIG. 13 are as follows. The resistance value of the resistor 102 was 2060Ω, and the resistance value of the resistor 106 was 155Ω. The resistance value of the resistor 112 was 1000Ω, and the value of the capacitor 110 was 3 pF. As the transistor, a multi-unit SiGe bipolar transistor incorporating a base ballast resistor (equivalent to 16Ω) was used. The capacitance of the impedance element 174 was set to 0.1F. A voltage of 2.9 V was applied to the bias terminal 100, and a voltage of 3.3 V was applied to the collector bias terminal 86, the bias terminal 170, and the bias terminal 240.

  Referring to FIG. 13, a graph 250 shows the relationship between the output voltage of the collector voltage of the transistor 242 included in the power amplifier 228 according to the present embodiment and the input signal power. A graph 252 shows the relationship between the output voltage of the collector voltage of the transistor 242 and the input signal power in the circuit shown in FIG.

  14 is a graph 260 showing the relationship between the base voltage of the transistor 88 included in the power amplifier 228 according to the present embodiment and the input signal power, and the VBE-dependent voltage source 230 shown in FIG. 12 is shown in FIG. A graph 262 shows the relationship between the base voltage of the transistor 88 included in the power amplifier replaced by the voltage source circuit having no input and the input signal power.

  Referring to FIG. 13, in the graph 250, the output voltage of the voltage source circuit fluctuated little up to an input signal level higher than that in the graph 252. As a result, as shown in FIG. 14, it can be seen that the graph 260 suppresses the decrease in the base voltage of the transistor 88 up to the input signal level higher than the graph 262.

  FIG. 15 is a graph 270 showing the relationship between the gain and the input signal level when the capacitance of the impedance element 174 included in the power amplifier 228 according to the third embodiment is 0.1 F, and 0.01 pF. A graph 272 shows the relationship between the gain and the input signal level.

  FIG. 16 is a graph 280 showing the relationship between the gain and the input signal power when the impedance of the impedance element 174 included in the power amplifier using the voltage source circuit of FIG. The relationship between the gain and the input signal power is shown by a graph 282, respectively.

  Referring to FIGS. 15 and 16, for example, when attention is paid to a 20 dBm input in which the base voltage is greatly different in FIG. 14, the gain in the graph 270 is about 9.2 dB, whereas the gain in the graph 280 is 8 The gain decreased to about 4 dB. In the graph 272, the gain is about 9.0 dBm, whereas in the graph 282, the gain is lowered to below 8 dBm. From these results, it can be seen that the power amplifier 228 according to the present embodiment has a low gain reduction and excellent linearity.

  This adjustment results in a slightly faster gain decrease at high input levels as a side effect of suppressing the temporary gain increase. However, in the configuration replaced with the voltage source circuit of FIG. 17 (graph 280), when the capacitance is reduced, the gain decrease at a high input level is rapidly accelerated as shown in the graph 282. As a result, the linearity is rather lowered. That is, in the conventional configuration in which the distortion compensation circuit and the voltage source circuit for temperature compensation are simply combined, the assumed distortion compensation effect may not be obtained at a high input signal level as in the graph 282.

  The inventors of the present invention can solve the above problems by using a base-emitter voltage type voltage source circuit having the configuration of the present invention, and can provide an amplifier having more linearity. It has also been found that a power amplifier circuit having high linearity using the base-emitter voltage type voltage source circuit of the configuration of the present invention can be configured.

  As a result of the examination, it has been found that the sharp decrease in gain at a high input level in the graph 282 is also caused by the input signal level dependency of the voltage source circuit. That is, when the impedance of the impedance element 174 decreases, a large AC signal voltage is applied to the output terminal of the VBE-dependent voltage source 230, causing a decrease in the output voltage. As a result, the base voltage of the transistor 88 is lowered and the gain is lowered.

  In the voltage source circuit in which the low-pass filter is connected to the base terminal of the transistor 242, the low-pass filter between the base terminal and the collector terminal of the transistor 244 that defines the base-emitter voltage of the VBE-dependent voltage source 230 in FIG. The configuration is such that the collector of the transistor 242 and the base terminal of the transistor 244 are short-circuited, and the low-pass filter 108 is connected between the emitter terminal of the transistor 244 and the base terminal of the transistor 242 instead.

  In the case of a circuit in which the above-described circuit terminals are connected instead of the VBE-dependent voltage source 230 of FIG. 12, the dependency on the input signal level as the voltage source circuit is not so small. There is almost no effect of improving linearity. This circuit is considered to be less effective because an AC signal is applied to the base terminal of the transistor 244 before the signal is attenuated by the low-pass filter 108.

  That is, when there are a plurality of transistors constituting the voltage source circuit, it is considered necessary to connect the low-pass filter 108 to the base terminal connected to the output terminal of the voltage source circuit as shown in FIG.

  As described above, the configuration of this embodiment can provide a power amplifier with high linearity.

  According to the present embodiment, it is not necessary to use an element that occupies a large area as in the first embodiment, so that an integrated circuit can be easily and inexpensively made.

[Fourth Embodiment]
<Configuration>
FIG. 18 shows an example of a wireless communication apparatus 300 using a power amplifier 314 according to the fourth embodiment of the present invention. Referring to FIG. 18, radio communication apparatus 300 is generated by baseband encoder 310 for generating a baseband signal, local transmitter 318 for transmitting a high-frequency signal, and baseband encoder 310. And a modulation unit 312 for modulating a high frequency signal generated from the local transmitter 318 by the baseband signal.

  The wireless communication apparatus 300 further includes a power amplifier 314 for amplifying the modulated wave modulated by the modulation unit 312, a control unit 316 for controlling a voltage applied to a control terminal of the power amplifier 314, and an output of the power amplifier 314. For switching circuits by selectively connecting the first and second terminals to the third terminal. Switch 326, and an antenna 328 connected to the third terminal of switch 326 for transmitting the modulated wave amplified by power amplifier 314 as a radio wave and receiving the radio wave.

  Wireless communication apparatus 300 further has an input connected to the second terminal of switch 326, low noise amplifier 324 for amplifying the signal received by antenna 328, the output of low noise amplifier 324, and a local oscillator By mixing the high frequency signal from 318, a demodulator 322 for demodulating the output of the low noise amplifier 324 into a baseband signal, and for extracting necessary data from the baseband signal demodulated by the demodulator 322 A baseband decoding unit 320.

  FIG. 19 is a circuit diagram showing the internal configuration of the power amplifier 314 according to the present embodiment. In FIG. 19, the same elements as those shown in FIGS. 2, 6, and 12 are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated here.

  Referring to FIG. 19, the power amplifier 314 according to the fourth embodiment is different from the power amplifier 228 shown in FIG. 12 in that a VBE dependent voltage source 230, instead of the distortion compensation circuit 152 in FIG. This is a point including a connection node between the matching circuit 82 and the transistor 88 and a distortion compensation circuit 334 connected to the control terminal 330.

  The distortion compensation circuit 334 differs from the distortion compensation circuit 152 shown in FIG. 12 in that it is connected between the base terminal of the transistor 172 and the ground instead of the impedance element 174 shown in FIG. The variable impedance circuit 340 whose impedance value changes is included.

  The variable impedance circuit 340 includes a capacitor 350 having one end connected to the base terminal of the transistor 172, a MOSFET 352 having a source terminal connected to the other end of the capacitor 350, and a grounded drain terminal, a MOSFET 352, and a control terminal 330. And a resistor 332 connected between them.

<Operation>
Referring to FIGS. 18 and 19, radio communication apparatus 300 employing power amplifier 314 according to the present embodiment operates as follows. Referring to FIG. 18, baseband encoding section 310 generates a baseband signal. The modulation unit 312 modulates the high-frequency signal generated from the local transmitter 318 by the generated baseband signal. The control unit 316 applies a control voltage to the control terminal 330 (see FIG. 19) of the power amplifier 314.

  A control voltage is applied from the control terminal 330 to the gate terminal of the MOSFET 352 through the resistor 332. By this application, the resistance between the source and drain of the MOSFET 352 changes. As a result, the impedance value of the entire variable impedance circuit 340 changes. Since other operations of power amplifier 314 are similar to those described in the third embodiment, detailed description thereof will not be repeated here.

  As described above, the power amplifier 314 amplifies the modulated wave modulated by the modulation unit 312. The antenna 328 outputs the amplified modulated wave as a radio wave via the switch 326.

  When the antenna 328 receives a radio wave, the low noise amplifier 324 amplifies the radio wave received by the antenna 328. The demodulator 322 demodulates the radio wave amplified by the low noise amplifier 324 into baseband. The baseband decoding unit 320 takes out necessary data from the baseband demodulated from radio waves.

<Comparison of results>
FIG. 20 shows the relationship between the gain of the power amplifier 314 shown in FIG. 19 and the input signal power when the control voltage is changed in order to finely adjust the effect of the distortion compensation circuit.

  Referring to FIG. 20, the characteristics of the circuit of FIG. 19 are shown by solid line graphs 360, 364, and 368, respectively. Characteristics of a configuration in which a circuit without the low-pass filter 108 shown in FIG. 17 is connected instead of the voltage source circuit of the circuit of FIG. 19 are shown by broken line graphs 362, 366, and 370, respectively.

Graphs 360 and 362 represent the relationship between the gain and the input signal when the control voltage is 2V. Graphs 364 and 366 represent the relationship between the gain and the input signal when the control voltage is 1V. Graphs 368 and 370 represent the relationship between the gain and the input signal when the control voltage is 0V.

  Even in the broken line graphs 362, 366, and 370 representing the results obtained by the configuration without the low-pass filter, the linearity of the gain is adjusted when the input power is in the range of -5 dBm to 10 dBm, for example, by changing the control voltage. it can. However, at a high input power of 10 dBm or more, particularly when the control voltage is 0 V, the gain is significantly reduced as shown by the portion 372 surrounded by the broken line in the graph 370, and the linearity of the gain is impaired.

  On the other hand, in the solid line graphs 360, 364, and 368 representing the results obtained by the circuit of FIG. 19, the input power dependence of the gain in the input signal in the range of −5 dBm to 15 dBm is adjusted by the change of the control voltage. it can. It can also be seen that the gain does not drop significantly even in a high output region of 15 dBm or more, and that the adjustment mechanism of the distortion compensation circuit 334 operates normally.

  According to radio communication apparatus 300 according to the present embodiment, for example, the control unit 316 can store the set value of the control voltage with respect to the power supply voltage for canceling fluctuations in the power supply voltage. Therefore, when the power supply voltage during operation varies, the voltage of the control terminal 330 of the power amplifier 314 can be controlled according to the power supply voltage. As a result, it is possible to provide a wireless device that can maintain the linearity of the power amplifier 314 in an optimum state.

  Similarly, the distortion of the power amplifier can be set to the minimum by configuring the control unit 316 to set the voltage of the control terminal 330 according to the operating state such as output power, frequency, or ambient temperature. Therefore, it is possible to provide a wireless communication apparatus with few communication errors.

  In radio communication apparatus 300 according to the present embodiment, gate voltage of MOSFET 352 is changed by control unit 316 in accordance with a change in input level and a change in power supply voltage. By this change, the impedance of the variable impedance circuit 340 is changed, and the effect of the distortion compensation circuit is finely adjusted according to the state of the power amplifier 314. However, the wireless communication device is not limited to this example.

  The power amplifier 314 of FIG. 19 used in the wireless communication apparatus 300 according to the present embodiment has a configuration in which the impedance element 174 of the power amplifier 228 according to the third embodiment is replaced with a variable impedance circuit 340. Similarly, in the power amplifier 148 according to the second embodiment, the impedance element 174 may be replaced with the variable impedance circuit 340.

  Further, in wireless communication apparatus 300 according to the present embodiment, the distortion compensation circuit is adjusted by the control voltage. However, the present invention is not limited to the configuration.

  In addition, the power amplifier 314 according to the present embodiment is used as a power amplifier having a single amplification element. However, the present invention can also be used in a multistage amplifier circuit in which amplifier elements are multistaged and a differential amplifier circuit that amplifies differential inputs.

  In the above embodiment, a SiGe bipolar transistor is used as the transistor. However, the transistor is not limited to a SiGe bipolar transistor. The present invention can be applied to all bipolar transistors such as Si and GaAs.

  The variable impedance circuit 340 shown in FIG. 19 uses a MOSFET as an element whose impedance can be changed. However, a general field effect transistor can also be used. In addition, a variable capacitance element such as a varactor diode can be used, and a voltage change of the parasitic capacitance of the transistor can also be used.

  In the above embodiment, a low-pass filter including a resistor and a capacitor and not including an inductance is used. However, the present invention is not limited to such an embodiment, and a low-pass filter including an inductance element may be used. However, when the inductance element is formed on a semiconductor integrated circuit, it occupies a large area and leads to an increase in the cost of the entire integrated circuit, which is not preferable. On the other hand, the series resistance used in the low-pass filter 108 of the above embodiment has a drawback of causing a voltage drop. However, because of the voltage drop that occurs for a much smaller base current relative to the collector current, the value of the voltage drop is small and has little effect.

  Further, the voltage drop due to the low-pass filter 108 can be corrected by slightly changing the values of the resistors 102 and 106, and this does not constitute a substantial defect. This is because a collector current and an emitter current flow through the resistors 102 and 106, respectively, and a slight change in the resistor 106 can cancel the voltage drop due to the series resistance of the low-pass filter 108.

  That is, in order to configure a low-cost integrated circuit, it is preferable to configure the voltage source circuit of the present invention using a configuration in which the low-pass filter 108 includes at least one series resistor.

  In the present embodiment, the low-pass filter 108 has a one-stage configuration including a resistor 112 and a capacitor 110. However, it is also possible to use a multistage low-pass filter with a plurality of resistors and capacitors. Further, an inductance may be used as the low pass filter.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by each claim in the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are intended. Including.

It is the schematic which shows the circuit structure of the general power amplifier 30 by a prior art. It is a circuit diagram which shows the structure of the power amplifier 70 which concerns on 1st Embodiment. It is the graph which showed the comparison of the circuit simulation of the temperature dependence with the case where temperature compensation is performed, and the case where temperature compensation is not performed. 6 is a graph showing the relationship between the output voltage and the input signal power of the transistor 104 as the output voltage of the power amplifier 70 according to the first embodiment and the conventional power amplifier 30 (see FIG. 1) without a low-pass filter. . 5 is a graph showing the relationship between the gain of the power amplifier and the input signal power in the same case as in FIG. It is a circuit diagram which shows the structure of the power amplifier 148 which concerns on 2nd Embodiment. Output voltage of the transistor 160 included in the power amplifier 148 according to the second embodiment and the transistor 160 when the VBE-dependent voltage source 150 of FIG. 6 is replaced by a voltage source circuit without the low-pass filter 108 shown in FIG. It is a graph which shows the relationship between and input signal power. The base voltage between the transistor 88 included in the power amplifier 148 according to the second embodiment and the transistor 88 when the VBE-dependent voltage source 150 of FIG. 6 is replaced by a voltage source circuit without the low-pass filter 108 shown in FIG. It is a graph which shows the relationship between and input signal power. It is a graph which shows the relationship between the gain of the power amplifier 148 which concerns on 2nd Embodiment, and input signal power when the capacity | capacitance of the impedance element 174 is 0.3 pF and 0.1 pF. 12 is a graph showing the relationship between the gain of the power amplifier using the voltage source circuit of FIG. 11 and the input signal power when the capacitance of the impedance element 174 is 0.3 pF and 0.1 pF. It is a figure which shows the voltage source circuit without the low-pass filter 108. It is a circuit diagram which shows the structure of the power amplifier 228 which concerns on 3rd Embodiment. Output voltage of the transistor 242 when the transistor 242 included in the power amplifier 228 according to the third embodiment and the VBE-dependent voltage source 230 of FIG. 12 are replaced by a voltage source circuit without the low-pass filter 108 shown in FIG. It is a graph which shows the relationship between and input signal power. The base voltage between the transistor 88 included in the power amplifier 228 according to the third embodiment and the transistor 88 when the VBE-dependent voltage source 230 of FIG. 12 is replaced by a voltage source circuit without the low-pass filter 108 shown in FIG. It is a graph which shows the relationship between and input signal power. It is a graph which shows the relationship between the gain of the power amplifier 228 which concerns on 3rd Embodiment, and an input signal level when the capacity | capacitance of the impedance element 174 is 0.1F and 0.01pF. 18 is a graph showing the relationship between the gain of the power amplifier using the voltage source circuit of FIG. 17 and the input signal power when the capacitance of the impedance element 174 is 0.1 F and 0.01 pF. 3 is a circuit diagram of a voltage source circuit without a low-pass filter 108. FIG. It is a figure which shows the example of the radio | wireless communication apparatus 300 using the power amplifier 314 which concerns on 4th Embodiment. It is a circuit diagram which shows the internal structure of the power amplifier 314 which concerns on 4th Embodiment. 20 is a graph showing the relationship between the gain of the power amplifier shown in FIG. 19 and the input signal power when the control voltage is changed to finely adjust the effect of the distortion compensation circuit.

Explanation of symbols

70, 148, 228, and 314 Power amplifier, 80 Signal input terminal, 82 and 90 Matching circuit, 84, 150, and 230 VBE dependent voltage source, 86 Collector bias terminal, 88, 104, 160, 162, 172, 242 , And 244 transistors, 92 signal output terminals, 100 and 240 bias terminals, 102, 106, 112, and 332 resistors, 108 low-pass filters, 110 and 350 capacitors, 174 impedance elements, 152 and 334 distortion compensation circuits, 330 control terminals, 340 Variable impedance circuit, 352 MOSFET

Claims (8)

An amplifier having a signal input terminal and a signal output terminal, and a first control terminal,
A collector terminal connected to the first potential and connected to output an output signal to the signal output terminal, an emitter terminal connected to the second potential, and an input signal received from the signal input terminal A first bipolar transistor having a base terminal connected to
A base bias circuit defining a base bias of the first bipolar transistor;
The base bias circuit is
A second bipolar transistor having a collector terminal connected to the base terminal of the first bipolar transistor;
A first resistor connected between a third potential and the collector terminal of the second bipolar transistor;
A low-pass filter that is conductive to direct current, connected between the collector terminal of the second bipolar transistor and a base terminal of the second bipolar transistor;
And the emitter terminal of said second bipolar transistor, seen including a second resistor connected between said second potential,
An amplifier in which a connection path between the collector terminal and the base terminal of the second bipolar transistor is only the low-pass filter .   The amplifier of claim 1, wherein the second potential is a ground potential. The low-pass filter includes a third resistor connected between the collector terminal and the base terminal of the second bipolar transistor;
3. The amplifier according to claim 1, further comprising a capacitive element connected between the second base terminal and the second potential.   The amplifier according to claim 1, further comprising a matching circuit connected between a signal input terminal and the base terminal.   The distortion compensation circuit is further connected between a connection point between the first resistor of the base bias circuit and the second bipolar transistor and the base terminal of the first bipolar transistor. The amplifier according to claim 4.   6. The third bipolar transistor according to claim 5, further comprising a third bipolar transistor having a collector terminal and a base terminal connected to the emitter terminal of the second bipolar transistor, and an emitter terminal connected to the second resistor. amplifier. The distortion compensation circuit includes:
A collector terminal connected to a fourth potential, a base terminal connected to a connection point between the first resistor and the collector terminal of the second bipolar transistor, and a base terminal of the first bipolar transistor; A fourth bipolar transistor having an emitter terminal connected thereto;
The amplifier according to claim 6, comprising an impedance element connected to the base terminal of the fourth bipolar transistor and the fourth potential. To any one of claims 1 to 7 comprising an amplifier as claimed, the wireless communication device.

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