JP2008172538A - Bias circuit and power amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To output stabler bias current with respect to the variation of power supply voltage. <P>SOLUTION: This bias circuit 100a for feeding bias current to a transistor 12 for amplification is provided with: a voltage source circuit connected to a Vbb power supply terminal 101 through a resistance 102 and including a first transistor 103 and a second transistor 104; a third transistor 106, wherein the Vbb power supply terminal 101 feeds the power to a collector terminal through a resistance 105, and a base terminal forms a current mirror with a base terminal of the second transistor 104; and a fourth transistor 108, wherein a base terminal is connected to the collector terminal of the third transistor 106, and an emitter terminal feeds bias current to a base terminal of the transistor 12 for amplification, and a resistance 110 for adjustment is provided between the base terminal of the second transistor 104 and the base terminal of the third transistor 106. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bias circuit and a power amplifier, and more particularly to a bias circuit that includes a bipolar transistor and has improved stability against fluctuations in power supply voltage, and a power amplifier that uses the bias circuit.

  2. Description of the Related Art Conventionally, there is a power amplifier (power amplifier) as one of essential electronic components in a transmission circuit such as a mobile phone. The power amplifier functions to amplify a low-power electric signal of several mW order generated by a signal processing IC (Integrated Circuit) at a stretch to a high power close to the W order and send it to the transmitting antenna.

  In recent years, MMIC (Microwave Monolithic Integrated Circuit) using GaAs-HBT (gallium arsenide-heterojunction bipolar transistor) has become the mainstream as a device form for power amplifiers. In the case of a bipolar power amplifier, there are two types of bias terminals to be supplied: a base bias terminal commonly called a “Vbb terminal” and a collector bias terminal commonly called a “Vcc terminal”.

  Here, the power amplifier is a component that handles large signal power by protruding among all electronic components of the mobile phone. Therefore, power amplifiers are emphasized from two viewpoints. First, since the superiority or inferiority of the power utilization efficiency of the power amplifier directly affects the battery consumption as it is, a highly efficient design technique is important. Secondly, since the power amplifier is one of the components where signal distortion due to nonlinearity is most likely to occur, a highly linear design technique is important.

  Therefore, in the bipolar power amplifiers that have become mainstream in recent years, what is important for realizing the high efficiency and the high linearity is that the bias circuit design of the Vbb terminal is particularly important. Are known.

  Therefore, as a conventional technique for designing a bias circuit, various circuit structures are disclosed in many documents. For example, a technique for improving the stability of a bias circuit is disclosed in Patent Document 1. Hereinafter, a bias circuit using the bias terminal of the Vbb terminal will be described consistently.

  FIG. 13 is a diagram showing a configuration of a conventional bias circuit 1000.

  The bias circuit 1000 is provided in the high frequency power amplifier 1500. Specifically, the high-frequency power amplifier 1500 includes an input terminal 1501, an amplification transistor 1502, and an output terminal 1503, and a bias circuit 1000 is provided to supply a bias current to the base terminal of the amplification transistor 1502. Yes. In the high frequency power amplifier 1500, the input / output matching circuit is omitted.

  As shown in FIG. 13, the bias circuit 1000 includes a Vbb power supply terminal 101, a resistor 102, a first transistor 103, a second transistor 104, a resistor 105, a third transistor 106, a resistor 107, a fourth transistor 108, and a resistor 109. I have.

  A Vbb power supply voltage is supplied to the Vbb power supply terminal 101, and the Vbb power supply terminal 101, the resistor 102, the first transistor 103, and the second transistor 104 constitute a VBE-dependent voltage source.

  The third transistor 106 forms a current mirror circuit with the second transistor 104, and its collector terminal is connected to the Vbb power supply terminal 101 via the resistor 105.

  The fourth transistor 108 is a transistor for supplying a bias current to the amplifying transistor 1502, the collector terminal is connected to the Vbb power supply terminal 101 via the resistor 107, the base terminal is connected to the collector terminal of the third transistor 106, The emitter terminal is connected to the base terminal of the amplifying transistor 1502 via the resistor 109.

  According to the above configuration, the current flowing through the resistor 102 is replicated by the current mirror circuit configured by the second transistor 104 and the third transistor 106. As a result, the duplicated current becomes a current reaching the Vbb power supply terminal 101 via the resistor 105.

  Therefore, a voltage is generated at the collector terminal of the third transistor 106 in a form corresponding to the voltage at the output terminal of the VBE-dependent voltage source (that is, the collector terminal of the first transistor 103). For example, if the mirror ratio of the current mirror circuit is 1 and the resistance values of the resistor 102 and the resistor 105 are the same, the voltage at the output terminal of the VBE-dependent voltage source is copied to the collector terminal of the third transistor 106.

  In this case, when the power supply voltage supplied to the Vbb power supply terminal 101 increases, the voltage at the output terminal of the VBE-dependent voltage source slightly increases. For this reason, the voltage at the collector terminal of the third transistor 106 also increases.

  However, since the current having the same value as the current flowing through the resistor 102 flows through the resistor 105 by the current mirror circuit, if the resistance value of the resistor 105 is set slightly larger than the resistance value of the resistor 102, the resistance value of the resistor 105 is large. More voltage drop will occur.

  That is, by adjusting the resistance value of the resistor 105, an effect of compensating for an increase in the voltage at the output terminal of the VBE-dependent voltage source when the voltage at the Vbb power supply terminal 101 increases is produced. Then, the base voltage of the fourth transistor 108 for bias supply is controlled by the terminal for outputting the compensated voltage (that is, the collector terminal of the third transistor 106), whereby Vbb in the collector current of the amplifying transistor 1502 can be obtained. It becomes possible to compensate the terminal voltage dependency.

  Next, FIG. 14 shows the result of simulating the Vbb power supply voltage fluctuation in the high-frequency power amplifier 1500 including the bias circuit 1000.

  FIG. 14 is a graph showing the relationship between the Vbb power supply voltage and the collector current of the amplifying transistor 1502. The horizontal axis represents the Vbb power supply voltage (V), and the vertical axis represents the collector current (A) of the amplifying transistor 1502.

  In this simulation, the resistance value of the resistor 102 is set to 1000Ω, the resistance value of the resistor 107 is set to 100Ω, and the resistance value of the resistor 109 is set to a fixed value of 100Ω. Further, when the resistance value of the resistor 105 is changed from 1000Ω to 1100Ω (10Ω step), the collector current of the amplifying transistor 1502 when the Vbb power supply voltage is varied from 2V to 10V is measured.

  Further, a curve x having the maximum maximum value with respect to the collector current of the amplifying transistor 1502 shows the result when the resistance value of the resistor 105 is set to 1000Ω, and the resistance 105 is successively decreased in order. The results are shown when the resistance value is changed from 1010Ω to 1090Ω every 10Ω steps. Finally, the curve y having the minimum maximum value shows the result when the resistance value of the resistor 105 is set to 1100Ω. For example, the point m1 indicates that when the resistance value of the resistor 105 is 1060Ω, the Vbb power supply voltage is 3.8V and the collector current of the amplifying transistor 1502 is 0.018A.

  As seen from the graph of FIG. 14, the collector current of the amplifying transistor 1502 decreases as the resistance value of the resistor 105 is made larger than the resistance value of the resistor 102. As a result, it can be seen that there is an effect of suppressing the bias current.

  The collector current of the amplifying transistor 1502 for each resistance value of the resistor 105 has a maximum value in the vicinity of 3 V to 4 V of the Vbb power supply voltage. For this reason, when this high-frequency power amplifier 1500 is used in the vicinity of the maximum Vbb power supply voltage, it can function as a bias circuit that can reduce the Vbb power supply voltage dependency of the collector current of the amplifying transistor 1502. Recognize.

Here, even when the resistance value of the resistor 102 and the resistance value of the resistor 105 are the same, the maximum value is due to the action based on the difference between the collector voltage of the second transistor 104 and the collector voltage of the third transistor 106. (Effect of early effect).
JP 2002-9558 A (published on January 11, 2002)

  However, in the conventional bias circuit 1000, as the resistance value of the resistor 105 is increased, correction for compensating for the increase in the voltage at the output terminal of the VBE-dependent voltage source by the voltage drop of the resistor 105 is more effective. The collector current of the amplifying transistor 1502 has a maximum value in the vicinity of 3 to 4 V, and has a problem that it rapidly decreases at a Vbb power supply voltage equal to or higher than the maximum value.

  Therefore, the bias circuit 1000 is required to output a more stable bias current against fluctuations in the power supply voltage.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a bias circuit and a power amplifier that can output a more stable bias current against power supply voltage fluctuations. is there.

  In order to solve the above problems, the bias circuit of the present invention is a bias circuit that supplies a bias current to the base terminal of the amplifying transistor, and is connected to the first power supply terminal via the first resistor. A voltage source circuit including a transistor, a collector terminal supplied with power from the first power supply terminal via a second resistor, an emitter terminal grounded, and a base terminal included in the voltage source circuit The base terminal of the reference transistor through which the same current as the current flowing through the first resistor among the plurality of transistors, the first transistor connected by forming a current mirror, and the collector terminal supply power from the second power supply terminal A base terminal connected to the collector terminal of the first transistor, and a via from the emitter terminal to the base terminal of the amplifying transistor. A second transistor for supplying current, both between the base terminal of the first transistor and the base terminal of the reference transistor, between the emitter terminal of the first transistor and ground, or between the two In addition, a third resistor is provided.

  According to the above configuration, the provision of the third resistor causes a slight potential difference between both ends of the third resistor. For this reason, the collector current of the first transistor replicated by the current mirror is a current slightly reduced from the current flowing through the first resistor.

  Therefore, when the power supply voltage supplied from the first power supply terminal is increased and the third resistor is not provided, the collector current of the first transistor is similarly adjusted in accordance with the increase in the current flowing through the first resistor. However, since the third resistor is provided, the current that flows through the first resistor increases, and the current that increases increases slightly. Therefore, the collector current of the first transistor to be replicated does not increase in proportion to the increase in the current flowing through the first resistor.

  Therefore, the voltage drop at the second resistor is reduced, and the voltage rise at the base terminal of the second transistor is advanced. As a result, the phenomenon that the voltage at the base terminal of the second transistor decreases due to the voltage drop in the second resistor can be mitigated and compensated. Therefore, the bias circuit of the present invention can output a more stable bias current against fluctuations in the power supply voltage.

  The plurality of transistors included in the voltage source circuit can be configured as follows.

  As a first configuration, the plurality of transistors included in the voltage source circuit include a third transistor having a collector terminal connected to the first resistor and a base terminal connected to its collector terminal, and the reference transistor. The reference transistor has a collector terminal connected to the emitter terminal of the third transistor, a base terminal connected to its collector terminal and the base terminal of the first transistor, and an emitter terminal grounded. It is preferable.

  As a second configuration, in the plurality of transistors included in the voltage source circuit, the collector terminal is supplied with power from the third power supply terminal, the base terminal is connected to the collector terminal of the reference transistor, and the emitter terminal is A fourth transistor connected to a base terminal of a reference transistor; and the reference transistor. The reference transistor has a collector terminal connected to the first resistor, an emitter terminal grounded, and a base terminal It is preferable to connect to the base terminal of the first transistor and to connect to the ground or the current source through the fourth resistor.

  In particular, according to the second configuration, the dependency of the power supply voltage is extremely low and stable on the lower voltage side than the fluctuation range of the power supply voltage capable of outputting a stable bias current according to the first configuration. It becomes possible to output a bias current.

  In the bias circuit of the present invention, the first resistor has a first terminal connected to the first power supply terminal and a second terminal connected to the voltage source circuit, and the first transistor Preferably, the collector terminal is connected to the second terminal of the first resistor via the second resistor.

  According to the above configuration, the collector terminal of the first transistor is connected to the second terminal of the first resistor via the second resistor, so that the potential of the second terminal of the first resistor in the second resistor. A voltage drop is performed with reference to. As a result, the upper limit of the voltage generated at the collector terminal of the first transistor, that is, the base terminal of the second transistor can be made lower than the potential of the second terminal of the first resistor.

  Therefore, even if some high voltage is erroneously applied to the first power supply terminal, it is possible to prevent the increased bias current from flowing into the amplifying transistor. It is also possible to prevent thermal runaway that occurs when a large current flows to generate heat and the transistor on-voltage decreases.

  The power amplifier according to the present invention is a power amplifier including a plurality of amplifying transistors connected in cascade and a bias circuit for supplying a bias current to each base terminal of the amplifying transistor, wherein the bias circuit includes: A voltage source circuit connected to a first power supply terminal via a first resistor, and including a plurality of transistors; a collector terminal is supplied with power from the first power supply terminal via a second resistor; The emitter terminal is grounded, and the base terminal is connected to the base terminal of a reference transistor through which the same current as the current flowing through the first resistor among the plurality of transistors included in the voltage source circuit is formed, forming a current mirror. The first transistor and the collector terminal are supplied with power from the second power supply terminal, and the base terminal is connected to the collector terminal of the first transistor. And a second transistor for supplying a bias current from the emitter terminal to the base terminal of the amplifying transistor, and a plurality of bias circuit units provided to be paired with the amplifying transistors. And in at least one bias circuit portion of the plurality of bias circuit portions, between the base terminal of the first transistor and the base terminal of the reference transistor, between the emitter terminal of the first transistor and the ground, Alternatively, a third resistor is provided between both of the two.

  According to the above configuration, the provision of the third resistor causes a slight potential difference between both ends of the third resistor. For this reason, the collector current of the first transistor replicated by the current mirror is a current slightly reduced from the current flowing through the first resistor.

  Therefore, when the power supply voltage supplied from the first power supply terminal is increased and the third resistor is not provided, the collector current of the first transistor is similarly adjusted in accordance with the increase in the current flowing through the first resistor. However, since the third resistor is provided, the current that flows through the first resistor increases, and the current that increases increases slightly. Therefore, the collector current of the first transistor to be replicated does not increase in proportion to the increase in the current flowing through the first resistor.

  Therefore, the voltage drop at the second resistor is reduced, and the voltage rise at the base terminal of the second transistor is advanced. As a result, the phenomenon that the voltage at the base terminal of the second transistor decreases due to the voltage drop in the second resistor can be mitigated and compensated. Therefore, the power amplifier according to the present invention can supply a more stable bias current to the amplifying transistor against fluctuations in the power supply voltage.

  The first transistor configured in each bias circuit section has a base terminal commonly connected to the base terminal of the reference transistor of the voltage source circuit, and a collector terminal connected to the first power supply terminal via the second resistor. Power is commonly supplied from. Therefore, each bias circuit section can share a voltage source circuit while forming a current mirror.

  Therefore, the power amplifier according to the present invention does not need to provide a voltage source circuit for each of the plurality of bias circuit units, and can be shared. Therefore, the current consumption can be reduced, the circuit scale can be reduced, and the size can be reduced. It becomes.

  The plurality of transistors included in the voltage source circuit can be configured as follows.

  As a first configuration, the plurality of transistors included in the voltage source circuit include a third transistor having a collector terminal connected to the first resistor and a base terminal connected to its collector terminal, and the reference transistor. The reference transistor has a collector terminal connected to the emitter terminal of the third transistor, a base terminal connected to its collector terminal and the base terminal of the first transistor, and an emitter terminal grounded. It is preferable.

  As a second configuration, in the plurality of transistors included in the voltage source circuit, the collector terminal is supplied with power from the third power supply terminal, the base terminal is connected to the collector terminal of the reference transistor, and the emitter terminal is A fourth transistor connected to a base terminal of a reference transistor; and the reference transistor. The reference transistor has a collector terminal connected to the first resistor, an emitter terminal grounded, and a base terminal It is preferable to connect to the base terminal of the first transistor and to connect to the ground or the current source through the fourth resistor.

  In particular, according to the second configuration, the dependency of the power supply voltage is extremely low and stable on the lower voltage side than the fluctuation range of the power supply voltage capable of supplying a stable bias current according to the first configuration. A bias current can be supplied.

  In the power amplifier according to the present invention, the first resistor has a first terminal connected to the first power supply terminal and a second terminal connected to the voltage source circuit. The collector terminal of at least one first transistor of one transistor is preferably connected to the second terminal of the first resistor through the second resistor.

  According to the above configuration, the collector terminal of the first transistor is connected to the second terminal of the first resistor via the second resistor, so that the potential of the second terminal of the first resistor in the second resistor. A voltage drop is performed with reference to. As a result, the upper limit of the voltage generated at the collector terminal of the first transistor, that is, the base terminal of the second transistor can be made lower than the potential of the second terminal of the first resistor.

  Therefore, even if some high voltage is erroneously applied to the first power supply terminal, it is possible to prevent the increased bias current from flowing into the amplifying transistor. It is also possible to prevent thermal runaway that occurs when a large current flows to generate heat and the transistor on-voltage decreases.

  As described above, the bias circuit of the present invention is connected to the first power supply terminal via the first resistor, the voltage source circuit including a plurality of transistors, and the collector terminal via the second resistor. The reference transistor is supplied with power from the first power supply terminal, the emitter terminal is grounded, and the base terminal of the reference transistor through which the same current as the current flowing through the first resistor among the plurality of transistors included in the voltage source circuit flows. A base terminal, a first transistor connected to form a current mirror, a collector terminal supplied with power from a second power supply terminal, a base terminal connected to the collector terminal of the first transistor, and an emitter terminal for amplification A second transistor for supplying a bias current to the base terminal of the transistor, and the base terminal of the first transistor and the reference transistor. Between the base terminal of the static, between the ground and the emitter terminal of the first transistor or both between the two, and the third provided a resistor, it has a configuration that.

  Therefore, by providing the third resistor, the collector current of the first transistor replicated by the current mirror is a current slightly reduced from the current flowing through the first resistor. Therefore, the voltage drop at the second resistor is reduced, and the voltage rise at the base terminal of the second transistor is advanced.

  As a result, the phenomenon that the voltage at the base terminal of the second transistor decreases due to the voltage drop in the second resistor can be mitigated and compensated. Therefore, it is possible to output a more stable bias current against fluctuations in the power supply voltage.

  In the power amplifier of the present invention, the bias circuit is connected to the first power supply terminal via the first resistor, the voltage source circuit including a plurality of transistors, and the collector terminal having the second resistor. The reference transistor is supplied with power from the first power supply terminal, the emitter terminal is grounded, and the base terminal has the same current as the current flowing through the first resistor among the plurality of transistors included in the voltage source circuit. The base terminal of the first transistor, the first transistor connected in the form of a current mirror, the collector terminal is supplied with power from the second power supply terminal, the base terminal is connected to the collector terminal of the first transistor, and is amplified from the emitter terminal A pair of amplifying transistors having a second transistor for supplying a bias current to the base terminal of the transistor for operation. A plurality of bias circuit portions provided, and in at least one bias circuit portion of the plurality of bias circuit portions, between the base terminal of the first transistor and the base terminal of the reference transistor, A third resistor is provided between the emitter terminal of the first transistor and the ground, or between the two.

  Therefore, by providing the third resistor, the collector current of the first transistor replicated by the current mirror is a current slightly reduced from the current flowing through the first resistor. Therefore, the voltage drop at the second resistor is reduced, and the voltage rise at the base terminal of the second transistor is advanced.

  As a result, the phenomenon that the voltage at the base terminal of the second transistor decreases due to the voltage drop in the second resistor can be mitigated and compensated. Therefore, it is possible to supply a more stable bias current against fluctuations in the power supply voltage.

  Each bias circuit section can share a voltage source circuit while forming a current mirror. Therefore, the voltage source circuit need not be provided for each of the plurality of bias circuit units, and can be shared. Thus, there is an effect that current consumption can be reduced, the circuit scale can be reduced, and the size can be reduced.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, components having functions equivalent to those of the conventional bias circuit 100a shown in FIG. 13 are denoted by the same reference numerals, and description thereof is omitted as appropriate.

  Note that the following transistors are npn bipolar transistors. However, the present invention is not limited to this, and a pnp bipolar transistor may be used as long as it has a function and effect of the present invention. For example, another transistor such as a MOS transistor may be suitably combined.

  FIG. 1 is a diagram illustrating a configuration example of the bias circuit 100a of the present embodiment.

  The bias circuit 100a of the present embodiment is provided in the high frequency power amplifier 10. Specifically, the high-frequency power amplifier 10 includes an input terminal 11, an amplification transistor 12, and an output terminal 13, and a bias circuit 100 a is provided to supply a bias current to the base of the amplification transistor 12. . The amplification transistor 12 has a base connected to the input terminal 11 and a collector connected to the output terminal 13. In the high frequency power amplifier 10, an input / output matching circuit is omitted.

  As shown in FIG. 1, the bias circuit 100a of the present embodiment includes a Vbb power supply terminal 101, a resistor 102, a first transistor 103, a second transistor 104, a resistor 105, a third transistor 106, a resistor 107, and a fourth transistor 108. , A resistor 109, and an adjustment resistor 110.

  A power supply voltage for Vbb is supplied to the Vbb power supply terminal 101, and the Vbb power supply terminal 101, the resistor 102, the first transistor 103, and the second transistor 104 constitute a VBE-dependent voltage source.

  The first transistor 103 has a base terminal connected to its collector terminal, and a collector terminal connected to the Vbb power supply terminal 101 via the resistor 102.

  The second transistor 104 has a base terminal connected to the base terminal of the third transistor 106 and its own collector terminal via the adjustment resistor 110, a collector terminal connected to the emitter terminal of the first transistor 103, and an emitter terminal Grounded.

  The third transistor 106 has a collector terminal connected to the Vbb power supply terminal 101 via the resistor 105, and an emitter terminal grounded. Note that the third transistor 106 forms a current mirror circuit with the second transistor 104 via the adjustment resistor 110.

  The adjustment resistor 110 is an adjustable resistor, for example, an adjustment resistor in which a thick film resistor formed on a ceramic substrate is trimmed by cutting with a laser. Further, a variable resistance component for surface mounting may be used, and the resistance value can be changed using a tool such as a screwdriver.

  The fourth transistor 108 is a transistor for supplying a bias current to the amplifying transistor 12. The fourth transistor 108 has a base terminal connected to the collector terminal of the third transistor 106, a collector terminal connected to the Vbb power supply terminal 101 via the resistor 107, and an emitter terminal connected to the amplifier transistor 12 via the resistor 109. Connected to the base terminal.

  Note that the voltage source circuit described in the claims indicates a circuit constituted by the first transistor 103 and the second transistor 104. As shown in FIG. 1, the same current as the current flowing through the resistor 102 flows through the first transistor 103 and the second transistor 104.

  Next, in the bias circuit 100a having the above configuration, the result of simulating the fluctuation of the Vbb power supply voltage will be described first, and then the characteristic operation of the bias circuit 100a showing the simulation result will be described.

  First, the result of simulating Vbb power supply voltage fluctuations in the high-frequency power amplifier 10 having the bias circuit 100a will be described with reference to FIG.

  FIG. 2 is a graph showing the relationship between the Vbb power supply voltage and the collector current of the amplifying transistor 12. The horizontal axis indicates the Vbb power supply voltage (V), and the vertical axis indicates the collector current (A) of the amplifying transistor 12.

  In this simulation, when the collector current of the amplifying transistor 12 is 30 mA, the resistance value of the resistor 102 is 1000Ω, the resistance value of the resistor 105 is 1070Ω, The resistance value is set to 100Ω, and the resistance value of the resistor 109 is set to a fixed value of 100Ω. Further, when the resistance value of the adjustment resistor 110 is changed from 0Ω to 100Ω (10Ω step), the collector current of the amplifying transistor 12 is measured when the Vbb power supply voltage is varied from 2V to 10V. In particular, the curve a shows the result when the resistance value of the adjustment resistor 110 is 67Ω.

  Here, in the simulation result in the configuration of the conventional bias circuit 1000 shown in FIG. 13, the collector current of the amplifying transistor 1502 has a maximum value in the vicinity of 3 to 4 V as shown in FIG. There is a sharp decrease in the Vbb power supply voltage which is larger than the value.

  On the other hand, in the simulation result in the configuration of the bias circuit 100a of the present embodiment shown in FIG. 1, the resistance value of the adjustment resistor 110 is adjusted as shown in FIG. The collector current is moderately reduced by 3 to 4 V or more of the Vbb power supply voltage.

  Particularly, in the curve a in which the resistance value of the adjusting resistor 110 is adjusted to 67Ω, when the Vbb power supply voltage is 4 to 7 V, the collector current of the amplifying transistor 12 is stable at 30 mA, and the Vbb dependence is extremely small. Has been created.

  Next, a characteristic operation of the bias circuit 100a according to the present embodiment, which reduces the rapid decrease in the collector current of the amplification transistor 12 shown in the simulation result of FIG. 2, will be described.

  By the way, in the conventional bias circuit 1000 shown in FIG. 13, the current flowing through the resistor 102 is duplicated by the current mirror circuit constituted by the second transistor 104 and the third transistor 106, and flows through the resistor 105. As a result, a voltage corresponding to the voltage at the collector terminal of the first transistor 103 is generated at the collector terminal of the third transistor 106.

  For this reason, in principle, the current mirror circuit that is close to the ideal of replicating the current more accurately and the adjustment of the relative relationship between the resistance values of the resistors 102 and 105 are very important roles in the bias circuit 1000. It has become. If the mirror ratio of the current mirror circuit is set to other than 1 and the resistance value of the resistor 105 is set to the reciprocal of the mirror ratio, the resistor 105 exhibits the same voltage drop and has the same effect.

  On the other hand, in the bias circuit 100a of the present embodiment shown in FIG. 1, the current duplication action by the current mirror circuit is intentionally shifted from an ideal proportional relationship. This will be described in detail below.

  When the adjustment resistor 110 is not provided, a current having the same value as the collector current flowing through the second transistor 104 flows through the collector terminal of the third transistor 106 due to the current mirror effect.

  However, when the adjustment resistor 110 is provided in series between the base terminal of the second transistor 104 and the base terminal of the third transistor 106, a slight potential difference is generated between both ends of the adjustment resistor 110.

  For this reason, when the base voltage of the third transistor 106 becomes lower than the base voltage of the second transistor 104, the collector current of the third transistor 106 becomes smaller than the collector current of the second transistor 104. That is, there is an effect of slightly reducing the replication current.

  As a result, when the adjustment resistor 110 is not provided when the Vbb power supply voltage increases, the collector current of the third transistor 106 increases in the same manner as the collector current of the second transistor 104 increases. In the case where the adjustment resistor 110 is provided, the third transistor 106 to be replicated acts to slightly reduce the increased replication current even if the collector current of the second transistor 104 is increased. The collector current of no longer increases in proportion.

  Further, the base voltage of the fourth transistor 108 for bias supply is controlled by the collector current of the third transistor 106. Thereby, the voltage of the output terminal of the bias circuit 100a, that is, the base voltage of the amplifying transistor 12 is controlled.

  Therefore, the voltage drop in the resistor 105 is reduced, and the voltage increase of the base voltage of the amplifying transistor 12 is advanced. As a result, the phenomenon that the output current of the bias circuit 100a decreases can be reduced and compensated.

  Therefore, the operation in the conventional bias circuit 1000 is to suppress the voltage increase at the output terminal of the bias circuit 1000 due to the voltage drop in the resistor 105, but the operation in the bias circuit 100a of the present embodiment is the adjustment resistor. It can be seen that the voltage increase at the output terminal of the bias circuit 100a is advanced by the action of slightly reducing the replication current by providing 110.

  If considered normally, if the above two actions act on the change in the power supply voltage of the Vbb power supply terminal 101, they cancel each other out and no particular effect is produced. That is, the two actions are the action of the prior art that suppresses the voltage rise at the output terminal due to the voltage drop and the action of the present invention that promotes the voltage rise at the output terminal by the action of reducing the replication current by the adjusting resistor 110.

  However, the inventors of the present invention, in the bias circuit 100a of the present embodiment, the above two actions act at different timings with respect to the change in the power supply voltage of the Vbb power supply terminal 101, and the output voltage As a result of simulation, a special effect that increases the effect of the stabilizing action was found.

  As described above, the bias circuit 100 a according to the present embodiment has a characteristic configuration in which the adjustment resistor 110 is provided between the base terminal of the second transistor 104 and the base terminal of the third transistor 106.

  As a result, when the adjustment resistor 110 is provided between the base terminal of the second transistor 104 and the base terminal of the third transistor 106, the current flowing through the resistor 102 varies with a change in the power supply voltage. The current that is replicated in is no longer proportional. That is, there is an effect of slightly reducing the replication current that increases when the Vbb power supply voltage increases. For this reason, the voltage drop generated in the resistor 105 is smaller than the value expected in the conventional bias circuit 1000.

  However, the inventors of the present invention can alleviate the “effect of abruptly reducing the collector current of the amplifying transistor 1502” generated in the configuration of the conventional bias circuit 1000 by providing the adjustment resistor 110. Found that there is. In addition, by appropriately setting the resistance value of the adjustment resistor 110, by adjusting the above-described action, it is possible to realize the bias circuit 100a having very little Vbb power supply voltage dependency in a wider Vbb voltage range. I found out that

  In the bias circuit 100a of this embodiment, the Vbb dependency is adjusted to be low when the collector current of the amplifying transistor 12 is 30 mA. However, the present invention is not limited to this, and each resistor (particularly the resistors 102 and 105) is adjusted. , And 110), it is possible to design a collector current value with low Vbb dependency.

  Further, the resistor 102 and the resistor 105 are connected to a power supply terminal having the same power supply voltage (that is, the Vbb power supply terminal 101), thereby forming a configuration in which the bias circuit 100a of the present embodiment compensates for the voltage dependency of the power supply terminal. Therefore, they are connected to the same terminal as shown in FIG.

  On the other hand, the resistor 107 is connected to the Vbb power supply terminal 101, but is not limited to this, and can be connected to another power supply terminal. However, since the resistor 107 is inserted so that the collector voltage of the fourth transistor 108 does not become too large, it is not an essential element of the bias circuit 100a.

  Further, the resistor 109 is used as a stabilizing resistor for preventing thermal runaway of the amplifying transistor 12, which is sometimes called a ballast resistor, and is not an essential element of the bias circuit 100a.

  In the bias circuit 100a, the adjustment resistor 110 is provided between the base terminal of the second transistor 104 and the base terminal of the third transistor 106. However, the present invention is not limited to this, and other configurations as shown in FIGS. The same effect can be obtained.

  FIG. 3 is a diagram illustrating a configuration example of the bias circuit 100b.

  The bias circuit 100b includes an adjustment resistor 111 as shown in FIG. 3 in addition to the configuration of the bias circuit 100a excluding the adjustment resistor 110. Thereby, the third transistor 106 is grounded via the adjusting resistor 111 at the emitter terminal.

  The adjustment resistor 111 has the same configuration as the adjustment resistor 110.

  According to the above configuration, the resistance value of the adjustment resistor 111 is very small, 1 / hfe of the adjustment resistor 110 inserted into the base terminal of the third transistor 106 of the bias circuit 100a, that is, about 0.4Ω. . Therefore, problems such as difficulty in incorporation into a circuit or increase in manufacturing resistance value are assumed.

  Therefore, it is more preferable that the adjustment resistor added to the bias circuit is placed in the base terminal of the third transistor 106.

  The bias circuit includes an adjustment resistor 110 provided between the base terminal of the second transistor 104 and the base terminal of the third transistor 106, and an adjustment resistor provided between the emitter terminal of the third transistor 106 and the ground. A configuration in which both the resistor 111 and the resistor 111 are provided may be employed.

  FIG. 4 is a diagram illustrating a configuration example of the bias circuit 100c.

  The bias circuit 100c includes a resistor 112, a resistor 113, and a fifth transistor 114 in addition to the configuration of the bias circuit 100a excluding the resistor 105.

  The resistors 112 and 113 are resistors obtained by dividing the resistor 105 illustrated in FIG.

  The fifth transistor 114 has a base terminal connected to its collector terminal via the resistor 113, a collector terminal connected to the Vbb power supply terminal 101 via the resistor 113 and the resistor 112 in this order, and an emitter terminal connected to the third transistor 106. Connected to the collector terminal.

  Thereby, the base terminal of the fourth transistor 108 is connected to the collector terminal of the fifth transistor 114.

  According to the above configuration, the fifth transistor 114 has the effect of equalizing the collector voltages of the second transistor 104 and the third transistor 106 constituting the current mirror circuit. As a result, there is an effect of making the operation of each transistor of the current mirror circuit ideal.

  For example, if the base current of the fifth transistor 114 is small and can be ignored, it can be seen that the sum of the resistor 112 and the resistor 113 acts as the resistor 105 and exhibits the same action. Therefore, it can be said that the configuration of the bias circuit 100c is substantially the same as the configuration of the bias circuit 100a shown in FIG.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  FIG. 5 is a diagram illustrating a configuration example of the bias circuit 200a of the present embodiment.

  As shown in FIG. 5, the bias circuit 200a of the present embodiment includes a Vbb power supply terminal 101, a resistor 102, a resistor 105, a third transistor 106, a resistor 107, a fourth transistor 108, a resistor 109, an adjustment resistor 110, a first resistor 110, 6 transistors 201, seventh transistors 202, resistors 203, and a power supply terminal 204 are provided.

  The sixth transistor 201 has a base terminal connected to the base terminal of the third transistor 106 via the adjustment resistor 110, a collector terminal connected to the Vbb power supply terminal 101 via the resistor 102, and an emitter terminal grounded. .

  The seventh transistor 202 has a base terminal connected to the collector terminal of the sixth transistor 201, a collector terminal connected to the power supply terminal 204, and an emitter terminal connected to the base terminal of the sixth transistor 201. The emitter terminal is also grounded via a resistor 203. However, instead of grounding via the resistor 203, it may be connected to a current source.

  The Vbb power supply terminal 101, the resistor 102, the sixth transistor 201, the seventh transistor 202, and the resistor 203 constitute a Vbb dependent voltage source.

  The third transistor 106 constitutes a current mirror circuit with the sixth transistor 201. The collector of the fourth transistor 108 is connected to the power supply terminal 204 via the resistor 107.

  Note that the voltage source circuit described in the claims indicates a circuit including the sixth transistor 201, the seventh transistor 202, the resistor 203, and the power supply terminal 204. As shown in FIG. 5, the same current as the current flowing through the resistor 102 flows through the sixth transistor 201.

  Next, in the bias circuit 200a having the above-described configuration, the result of simulating Vbb power supply voltage fluctuation will be described first, and then the characteristic operation of the bias circuit 200a showing the simulation result will be described.

  First, a simulation result of Vbb power supply voltage fluctuation in the high-frequency power amplifier 10 including the bias circuit 200a will be described with reference to FIG.

  FIG. 6 is a graph showing the relationship between the Vbb power supply voltage and the collector current of the amplifying transistor 12. The horizontal axis indicates the Vbb power supply voltage (V), and the vertical axis indicates the collector current (A) of the amplifying transistor 12.

  In this simulation, when the collector current of the amplifying transistor 12 is 30 mA, the resistance value of the resistor 102 is 1000Ω, the resistance value of the resistor 105 is 1070Ω, The resistance value is set to 100Ω, and the resistance value of the resistor 109 is set to a fixed value of 100Ω. Moreover, the result in each resistance value when the resistance value of the adjustment resistor 110 is swung from 0Ω to 100Ω (10Ω step) is measured. In particular, the curve b shows the result when the resistance value of the adjustment resistor 110 is 50Ω.

  Here, in the simulation result with the configuration of the bias circuit 100a of the first embodiment shown in FIG. 1, when the resistance value of the adjustment resistor 110 is adjusted to 67Ω as shown by the curve a in FIG. With respect to the collector current of the transistor 12 for the transistor, when the Vbb voltage is 4 to 7 V, a region having extremely small Vbb dependence can be created.

  On the other hand, in the simulation result in the configuration of the bias circuit 200a of the present embodiment shown in FIG. 5, the resistance value of the adjustment resistor 110 is adjusted as shown in FIG. The collector current is moderately reduced by 3 to 4 V or more of the Vbb power supply voltage.

  In particular, in the curve b in which the resistance value of the adjusting resistor 110 is adjusted to 50Ω, when the Vbb power supply voltage is 2.8 V to 4.5 V, the collector current of the amplifying transistor 12 is stabilized at 30 mA, and depends on Vbb. A very small area has been created.

  Thereby, in the bias circuit 200a, a region having extremely small Vbb dependency can be created on the lower voltage side than the fluctuation range of the Vbb power supply voltage in which a stable bias current can be output by the bias circuit 100a. It is possible.

  Next, a characteristic operation of the bias circuit 200a of the present embodiment that mitigates the rapid decrease in the collector current of the amplifying transistor 12 shown in the simulation result of FIG. 6 will be described.

  Here, a circuit including the sixth transistor 201, the seventh transistor 202, and the resistor 203 is a circuit with low dependency on the power supply voltage of the Vbb power supply terminal 101 and the power supply terminal 204. This will be described.

  The sixth transistor 201 and the seventh transistor 202 are in a feedback relationship for correcting each other. That is, the input terminal (base terminal) and the output terminal (collector terminal) of the sixth transistor 201 are connected to the output terminal (emitter terminal) and the input terminal (base terminal) of the seventh transistor 202, respectively.

  The sixth transistor 201 has a collector terminal connected to the Vbb power supply terminal 101 via the resistor 102 and an emitter terminal grounded. The seventh transistor 202 has a collector terminal connected to the power supply terminal 204 and an emitter terminal grounded via a resistor 203.

  Therefore, in the bias circuit 200a, the base potential of the sixth transistor 201 and the base potential of the seventh transistor 202 are separated from the Vbb power supply terminal 101 and the power supply terminal 204 in a circuit manner, regardless of the fluctuation of the power supply voltage. The base potential of the sixth transistor 201 and the base potential of the seventh transistor 202 are kept constant.

  Thus, the circuit including the resistor 102, the sixth transistor 201, the seventh transistor 202, and the resistor 203 is stabilized against fluctuations in the power supply voltage. That is, the circuit is less dependent on the power supply voltage of the Vbb power supply terminal 101 and the power supply terminal 204.

  The sixth transistor 201 and the third transistor 106 form a current mirror circuit. Therefore, if the adjustment resistor 110 is not provided, a current having the same value as the collector current flowing through the sixth transistor 201 flows through the collector terminal of the third transistor 106 due to the current mirror effect.

  However, since the adjustment resistor 110 is provided in the bias circuit 200a, the base voltage of the third transistor 106 is lower than the base voltage of the sixth transistor 201. In addition, the base voltage of the sixth transistor 201 is stabilized against fluctuations in the power supply voltage as described above, and has low dependency on the power supply voltage. For this reason, it is considered that the base voltage of the third transistor 106 is affected by the stabilization effect intended for the fluctuation of the power supply voltage.

  As a result, the collector current of the third transistor 106 becomes smaller than the collector current of the sixth transistor 201. In other words, the bias circuit 100a of the first embodiment has the effect of slightly reducing the replication current described above.

  Further, the base voltage of the fourth transistor 108 for bias supply is controlled by the collector current of the third transistor 106. Thereby, the voltage of the output terminal of the bias circuit 200a, that is, the base voltage of the amplifying transistor 12 is controlled.

  Therefore, in the bias circuit 200a, the phenomenon that the voltage of the base terminal of the amplifying transistor 12 decreases can be reduced and compensated by reducing the voltage drop in the resistor 105.

  Therefore, the operation of the bias circuit 200a of the present embodiment is similar to the operation of the bias circuit 100a of the above-described embodiment, and the output of the bias circuit 200a is slightly reduced by the operation of slightly reducing the replication current by providing the adjustment resistor 110. It can be seen that the voltage rise at the terminal is advanced.

  Further, the inventors of the present invention have different connection timings of the sixth transistor 201, the seventh transistor 202, and the resistor 203, and the above two actions at different timings with respect to changes in the power supply voltage of the Vbb power supply terminal 101. The bias circuit 200a according to the present embodiment has an extremely small Vbb dependency on the lower voltage side than the bias circuit 100a according to the first embodiment by the action of the unique structure in combination with the working structure. As a result of the simulation, the effect that it is possible to create is found.

  In general, when a usable power supply voltage is large, it is relatively easy to form a constant voltage circuit or a constant current circuit using a transistor circuit. Conversely, when the same thing is performed in a region where the available power supply voltage is low, it becomes more difficult. This also applies to the power amplifier circuit of the present invention.

  However, according to the configuration of the bias circuit 200a of the present embodiment, it is possible to provide a power amplifier having a low Vbb bias dependency in a low voltage region. Therefore, the configuration of the bias circuit 200a of this embodiment is extremely useful.

  In the bias circuit 200a of the present embodiment, the Vbb dependency is adjusted to be low when the collector current of the amplifying transistor 12 is 30 mA. However, the bias circuit 200a is not limited to this, and the bias circuit of the first embodiment is not limited thereto. Similarly to 100a, it is possible to design a collector current value having low Vbb dependency by adjusting each resistor (especially resistors 102, 105, and 110).

  Further, the resistor 102 and the resistor 105 are connected to a power supply terminal having the same power supply voltage (that is, the Vbb power supply terminal 101), so that the voltage dependency of the power supply terminal is reduced as in the bias circuit 100a of the first embodiment. Since the configuration compensated by the bias circuit 200a of the embodiment is formed, they are connected to the same terminal as shown in FIG.

  On the other hand, the resistor 107 is connected to the power supply terminal 204, but is not limited thereto, and can be connected to another power supply terminal, for example, the Vbb power supply terminal 101. Similarly, the collector terminal of the seventh transistor 202 can be connected to another power supply terminal, for example, the Vbb power supply terminal 101.

  In the bias circuit 200a, the adjustment resistor 110 is provided between the base terminal of the sixth transistor 201 and the base terminal of the third transistor 106. However, the present invention is not limited to this, and other configurations as shown in FIGS. The same effect can be obtained.

  FIG. 7 is a diagram illustrating a configuration example of the bias circuit 200b.

  In addition to the configuration of the bias circuit 200a excluding the adjustment resistor 110, the bias circuit 200b includes an adjustment resistor 111 as shown in FIG. Thereby, the third transistor 106 is grounded via the adjusting resistor 111 at the emitter terminal.

  According to the above configuration, the resistance value of the adjustment resistor 111 is very small, such as 1 / hfe of the adjustment resistor 110 inserted into the base terminal of the third transistor 106 of the bias circuit 200a, that is, about 0.4Ω. . Therefore, problems such as difficulty in incorporation into a circuit or increase in manufacturing resistance value are assumed.

  Therefore, it is more preferable that the adjustment resistor added to the bias circuit is placed in the base terminal of the third transistor 106.

  The bias circuit includes an adjustment resistor 110 provided between the base terminal of the sixth transistor 201 and the base terminal of the third transistor 106, and an adjustment resistor provided between the emitter terminal of the third transistor 106 and the ground. A configuration in which both the resistor 111 and the resistor 111 are provided may be employed.

  FIG. 8 is a diagram illustrating a configuration example of the bias circuit 200c.

  The bias circuit 200c includes an eighth transistor 205 in addition to the configuration of the bias circuit 200a.

  The eighth transistor 205 has a collector terminal connected to the Vbb power supply terminal 101 via the resistor 102, and an emitter terminal connected to the collector terminal of the sixth transistor 201. The base terminal is connected to the base of the seventh transistor 202 and to the collector terminal of the seventh transistor 202.

  Thereby, the base terminal of the seventh transistor 202 is connected to the base terminal of the eighth transistor 205.

  Also in the above configuration, the circuit constituted by the Vbb power supply terminal 101, the resistor 102, the sixth transistor 201, the seventh transistor 202, the resistor 203, and the power supply terminal 204 functions as a VBE-dependent voltage source. That is, in the present invention, a minute change of the circuit constituting the VBE-dependent voltage source is not the essence of the invention but is included in the present invention.

  In the bias circuit 200c, the collector voltage of the sixth transistor 201 constituting the current mirror is lower than the collector voltage of the third transistor 106. For this reason, the mirror current (that is, the collector current of the third transistor 106) becomes large, which is preferable because it has an effect of suppressing a rapid increase in the collector current in the region where the Vbb voltage is high in FIG.

[Embodiment 3]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first and second embodiments. For convenience of explanation, members having the same functions as those shown in the drawings of the first and second embodiments are given the same reference numerals, and explanation thereof is omitted.

  FIG. 9 is a diagram illustrating a configuration example of the bias circuit 300a of the present embodiment.

  The bias circuit 300a of the present embodiment includes a resistor 301 and a resistor 302 as shown in FIG. 9 in addition to the configuration of the bias circuit 200a of the above-described embodiment except for the resistor 102 and the resistor 105.

  Thereby, the collector terminal of the sixth transistor 201 is connected to the Vbb power supply terminal 101 via the resistor 301. The collector terminal of the third transistor 106 is connected to the collector terminal of the sixth transistor via the resistor 302.

  Next, in the bias circuit 300a having the above-described configuration, the simulation result of the Vbb power supply voltage fluctuation is described first, and then the characteristic operation of the bias circuit 300a showing the simulation result is described.

  First, the result of simulating Vbb power supply voltage fluctuations in the high-frequency power amplifier 10 having the bias circuit 300a will be described with reference to FIG.

  FIG. 10 is a graph showing the relationship between the Vbb power supply voltage and the collector current of the amplifying transistor 12. The horizontal axis indicates the Vbb power supply voltage (V), and the vertical axis indicates the collector current (A) of the amplifying transistor 12.

  In this simulation, when the collector current of the amplification transistor 12 is 30 mA, the resistance value of the resistor 301 is 500Ω, the resistance value of the resistor 302 is 100Ω, The resistance value is set to 100Ω, and the resistance value of the resistor 109 is set to a fixed value of 100Ω. Moreover, the result in each resistance value when the resistance value of the adjustment resistor 110 is swung from 0Ω to 100Ω (10Ω step) is measured. In particular, the curve c shows the result when the resistance value of the adjustment resistor 110 is 60Ω.

  Here, in the simulation result with the configuration of the bias circuit 200a of the second embodiment shown in FIG. 5, the Vbb voltage is 2 with respect to the collector current of the amplifying transistor 12, as shown by the curve b in FIG. A region having extremely small Vbb dependence can be created when .8 to 4.5V. However, a sudden increase in current occurs at a Vbb voltage higher than that.

  On the other hand, in the simulation result with the configuration of the bias circuit 300a of the present embodiment shown in FIG. 9, the resistance value of the adjustment resistor 110 is adjusted as shown in FIG. The collector current does not increase rapidly even when the Vbb power supply voltage is increased to 10V.

  In particular, in the curve c in which the resistance value of the adjustment resistor 110 is adjusted to 60Ω, even when the Vbb power supply voltage is increased to 10V, the collector current of the amplifying transistor 12 is stabilized at 30 mA, and the Vbb dependency is extremely small. An area has been created.

  Thereby, in the bias circuit 300a, a region having extremely small Vbb dependence is provided on the higher voltage side than the fluctuation range of the Vbb power supply voltage in which a stable bias current can be output by the bias circuit 100a and the bias circuit 200a. It is possible to create.

  Next, a characteristic operation of the bias circuit 300a of the present embodiment that reduces the rapid decrease in the collector current of the amplifying transistor 12 shown in the simulation result of FIG. 10 will be described.

  Here, in the simulation shown in FIGS. 2 and 6, the resistance value of the resistor 102 is set to 1000Ω, and the resistance value of the resistor 105 is set to 1070Ω.

  On the other hand, in the simulation shown in FIG. 10, the resistance value of the resistor 301 is set to 500Ω so as to correspond to the parallel connection of the resistor 102 and the resistor 105. Then, the action caused by setting the resistance value of the resistor 105 to be larger than the resistance value of the resistor 102 is replaced by adding the resistor 302.

  That is, in the bias circuit 300a, the sixth transistor 201 and the third transistor 106 constitute a current mirror circuit, and therefore generate substantially the same current. However, the voltage drop is increased by the amount of the resistor 302, and the collector voltage of the third transistor 106 is lowered. At this time, the adjustment resistor 110 is added to the current mirror circuit in order to generate the same action as in the first and second embodiments.

  Further, the output voltage of the VBE-dependent voltage source has a voltage dependency on the Vbb power supply voltage, but has a constant voltage source action as the name of the voltage source.

  Conventionally, in the bias circuits of the first and second embodiments, as described above, the output voltage of the VBE-dependent voltage source is duplicated by the current mirror circuit, and the duplicated current source and resistor are used. , A voltage substantially close to the output voltage of the VBE dependent voltage source is generated.

  For this reason, when the Vbb power supply voltage exceeds the design range, the voltage may deviate significantly from the expected voltage. For example, in the bias circuit of the second embodiment, the phenomenon that the current greatly increases when the Vbb voltage is 5 V or more is actually related to this action.

  On the other hand, in the bias circuit 300a of the present embodiment, the duplicated current also has the function of dropping the voltage by the resistance 302. However, by lowering the voltage with reference to the collector voltage of the sixth transistor 201, that is, the output voltage of the VBE dependent voltage source, the upper limit of the voltage generated at the collector terminal of the third transistor 106 is set to the output of the VBE dependent voltage source. The configuration does not exceed the voltage.

  Thereby, in the bias circuit 300a, the collector current of the amplifying transistor 12 is prevented in principle from being extremely increased by the set value of Vbb.

  In general, in a circuit constituted by bipolar transistors, there is a possibility that heat is generated by flowing a large current, the on-voltage of the bipolar transistor is lowered, and the current is repeatedly increased. This is called thermal runaway.

  For this reason, it is important that the circuit is configured not to flow a large current even if some erroneous voltage is applied. In particular, in a power amplifier having a high output, since the collector current is connected to a power supply having a large allowable amount, an element may be damaged due to an overcurrent.

  However, in the bias circuit 300a of the present embodiment, the collector terminal of the third transistor is connected to the collector voltage of the sixth transistor 201, in other words, the Vbb power supply terminal 101 via the resistor 301, whereby the Vbb terminal is connected to the Vbb terminal. Even when a high voltage is improperly applied, the collector current of the amplifying transistor 12 does not flow a large current. Therefore, the bias circuit 300a is particularly useful for a power amplifier circuit having a high output.

  Further, in the bias circuit 300a, the connection configuration of the resistor 301 and the resistor 302 is applied to the configuration of the bias circuit 200a illustrated in FIG. 5, but the configuration is not limited to this and may be applied to the configuration of other bias circuits described above. Is possible. For example, FIG. 11 shows an example applied to the configuration of the bias circuit 100a shown in FIG.

  FIG. 11 is a diagram illustrating a configuration example of the bias circuit 300b according to the present embodiment.

  The bias circuit 300b includes a resistor 301a, a resistor 301b, and a resistor 302 as shown in FIG. 11 in addition to the configuration of the bias circuit 100a of the above-described embodiment excluding the resistor 102 and the resistor 105.

  The resistors 301a and 301b are resistors obtained by dividing the resistor 301 illustrated in FIG.

  Thus, the collector terminal of the second transistor 104 is connected to the Vbb power supply terminal 101 via the resistor 301a and the resistor 301b in this order. The collector terminal of the third transistor 106 is connected to the collector terminal of the first transistor 103 through the resistor 302 and the resistor 301b in this order.

  In the bias circuit 300b, the collector terminal of the third transistor 106 is connected between the resistor 301a and the resistor 301b, but the resistor 301 is provided without dividing the resistor 301a and the resistor 301b. The collector terminal of the third transistor 106 may be directly connected to the collector terminal of the transistor 103.

[Embodiment 4]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first to third embodiments. For convenience of explanation, members having the same functions as those shown in the drawings of Embodiments 1 to 3 are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 12 is a diagram illustrating a configuration example of the high-frequency power amplifier 50 according to the present embodiment.

  As shown in FIG. 12, the high-frequency power amplifier 50 of this embodiment includes an input terminal 51, an amplifying transistor 52, a matching circuit 53, an amplifying transistor 54, a matching circuit 55, an amplifying transistor 56, an output terminal 57, and a common. A bias circuit unit 58 and bias circuit units 59a to 59c are provided.

  The high frequency power amplifier 50 is a three-stage amplifier that is amplified in three stages by an amplifying transistor 52, an amplifying transistor 54, and an amplifying transistor 56. Specifically, in the high-frequency power amplifier 50, three amplification transistors 52, 54 and 56 are connected in cascade between the input terminal 51 and the output terminal 57 with the two matching circuits 53 and 55 interposed therebetween. It has the composition which is.

  Further, the portion constituted by the common bias circuit portion 58 and the bias circuit portions 59a to 59c is a bias circuit for the three-stage amplifier. The high-frequency power amplifier 50 is configured using the bias circuit 100a shown in FIG.

  The common bias circuit unit 58 corresponds to the circuit including the Vbb power supply terminal 101, the resistor 102, the first transistor 103, and the second transistor 104 shown in FIG. 1 and has a similar configuration.

  The bias circuit portions 59a to 59c correspond to the circuit including the resistor 105, the third transistor 106, the resistor 107, the fourth transistor 108, the resistor 109, and the adjustment resistor 110 shown in FIG. It is a circuit having. The output terminal of the bias circuit unit 59a is connected to the base terminal of the amplifying transistor 52. The output terminal of the bias circuit unit 59b is connected to the base terminal of the amplifying transistor 54. The output terminal of the bias circuit portion 59 c is connected to the base terminal of the amplifying transistor 56.

  Here, the second transistor 104 of the common bias circuit unit 58 and the third transistor 106 of the bias circuit units 59a to 59c each constitute a current mirror circuit. That is, the bias circuit units 59a to 59c share the common bias circuit unit 58 and refer to the same voltage.

  Therefore, in the high-frequency power amplifier 50 according to the present embodiment, the current mirror circuit configured by the second transistor 104 and the third transistor 106 is configured to generate three types of replication currents instead of one replication current. Thus, each of the replication currents is used to generate a bias current for each of the amplifying transistors 52, 54, and 56.

  Therefore, in the power amplifier of the present invention, the common bias circuit unit 58 can supply each of the amplifying transistors 52, 54, and 56 with a more stable bias current against fluctuations in the power supply voltage. It is not necessary to prepare each amplifying transistor, and it can be shared. Therefore, current consumption in the entire bias circuit can be reduced.

  At the same time, since the common bias circuit unit 58 can be shared, the circuit area can be reduced, leading to a reduction in size and cost of the high-frequency power amplifier 50.

  Further, the high-frequency power amplifier 50 according to the present embodiment is configured using the bias circuit 100a illustrated in FIG. 1, but is not limited thereto, and may be configured using another bias circuit described above. Furthermore, not only a three-stage amplifier but also a multistage amplifier may be configured.

  It is more preferable that the bias circuit units 59a to 59c reduce the power supply voltage dependency in the entire circuit by performing correction using the adjustment resistor 110, which is the essence of the configuration of the present invention. The present invention is not limited to application to a bias circuit for all amplifying transistors.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the present invention can be obtained by appropriately combining technical means disclosed in different embodiments. Such embodiments are also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention is particularly effective in realizing a bias circuit that outputs a more stable bias current against power supply voltage fluctuations and a power amplifier including the bias circuit, and is suitable for mobile communication such as mobile phones and wireless LANs. It can be suitably used for a high-frequency power amplifier and a mobile communication terminal used.

It is a circuit diagram which shows one Embodiment of the bias circuit in this invention. It is a graph which shows the relationship between the power supply voltage and output current in the said bias circuit. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a graph which shows the relationship between the power supply voltage and output current in the said bias circuit. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a graph which shows the relationship between the power supply voltage and output current in the said bias circuit. It is a circuit diagram which shows other embodiment of the bias circuit in this invention. It is a circuit diagram which shows one Embodiment of the power amplifier in this invention. It is a circuit diagram which shows the structure of the conventional bias circuit. It is a graph which shows the relationship between a power supply voltage and output current in the said conventional bias circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 50 High frequency power amplifier 12, 52, 54, 56 Amplifying transistor 58 Common bias circuit part 59a-59c Bias circuit part 100a-100c Bias circuit 101 Vbb power supply terminal (1st power supply terminal, 2nd power supply terminal)
102 Resistance (first resistance)
103 1st transistor (3rd transistor)
104 Second transistor (reference transistor)
105 Resistance (second resistance)
106 third transistor (first transistor)
107 resistor 108 fourth transistor (second transistor)
109 Resistor 110, 111 Adjusting resistor (third resistor)
112, 113 Resistor 114 Fifth transistor 200a to 200c Bias circuit 201 Sixth transistor (reference transistor)
202 7th transistor (4th transistor)
203 Resistance (4th resistance)
204 power terminal (third power terminal, second power terminal)
205 Eighth transistor 300a, 300b Bias circuit 301 Resistance (first resistance)
301a resistor 301b resistor 302 resistor (second resistor)

Claims (8)

A bias circuit for supplying a bias current to a base terminal of an amplifying transistor,
A voltage source circuit connected to the first power supply terminal via the first resistor and configured to include a plurality of transistors;
The collector terminal is supplied with power from the first power supply terminal via the second resistor, the emitter terminal is grounded, and the base terminal is a current flowing through the first resistor among the plurality of transistors included in the voltage source circuit. A base terminal of a reference transistor through which the same current flows, a first transistor connected to form a current mirror,
A collector terminal having power supplied from a second power supply terminal, a base terminal connected to the collector terminal of the first transistor, and a second transistor supplying bias current from the emitter terminal to the base terminal of the amplifying transistor;
A third resistor is provided between the base terminal of the first transistor and the base terminal of the reference transistor, between the emitter terminal of the first transistor and the ground, or between the two. Bias circuit. The plurality of transistors included in the voltage source circuit are:
A third transistor having a collector terminal connected to the first resistor and a base terminal connected to its collector terminal;
Including the reference transistor,
The reference transistor has a collector terminal connected to the emitter terminal of the third transistor, a base terminal connected to its collector terminal and the base terminal of the first transistor, and an emitter terminal grounded. The bias circuit according to claim 1. The plurality of transistors included in the voltage source circuit are:
A fourth transistor having a collector terminal supplied with power from a third power supply terminal, a base terminal connected to the collector terminal of the reference transistor, and an emitter terminal connected to the base terminal of the reference transistor;
Including the reference transistor,
The reference transistor has a collector terminal connected to the first resistor, an emitter terminal grounded, a base terminal connected to the base terminal of the first transistor, and grounded via a fourth resistor, or The bias circuit according to claim 1, wherein the bias circuit is connected to a current source. The first resistor has a first terminal connected to the first power supply terminal and a second terminal connected to the voltage source circuit,
2. The bias circuit according to claim 1, wherein a collector terminal of the first transistor is connected to a second terminal of the first resistor via the second resistor. A power amplifier comprising a plurality of amplifying transistors connected in cascade and a bias circuit for supplying a bias current to each base terminal of the amplifying transistor,
The bias circuit is
A voltage source circuit connected to the first power supply terminal via the first resistor and configured to include a plurality of transistors;
The collector terminal is supplied with power from the first power supply terminal via the second resistor, the emitter terminal is grounded, and the base terminal is a current flowing through the first resistor among the plurality of transistors included in the voltage source circuit. The base terminal of the reference transistor through which the same current flows, the first transistor connected to form a current mirror, the collector terminal is supplied with power from the second power supply terminal, and the base terminal is connected to the collector terminal of the first transistor. And a plurality of bias circuit portions provided to be paired with the plurality of amplification transistors, the second transistor supplying a bias current from the emitter terminal to the base terminal of the amplification transistor. And
In at least one bias circuit portion of the plurality of bias circuit portions, between the base terminal of the first transistor and the base terminal of the reference transistor, between the emitter terminal of the first transistor and ground, or the above A power amplifier characterized in that a third resistor is provided between the two. The plurality of transistors included in the voltage source circuit are:
A third transistor having a collector terminal connected to the first resistor and a base terminal connected to its collector terminal;
Including the reference transistor,
The reference transistor has a collector terminal connected to the emitter terminal of the third transistor, a base terminal connected to its collector terminal and the base terminal of the first transistor, and an emitter terminal grounded. The power amplifier according to claim 5. The plurality of transistors included in the voltage source circuit are:
A fourth transistor having a collector terminal supplied with power from a third power supply terminal, a base terminal connected to the collector terminal of the reference transistor, and an emitter terminal connected to the base terminal of the reference transistor;
Including the reference transistor,
The reference transistor has a collector terminal connected to the first resistor, an emitter terminal grounded, a base terminal connected to the base terminal of the first transistor, and grounded via a fourth resistor, or The power amplifier according to claim 5, wherein the power amplifier is connected to a current source. The first resistor has a first terminal connected to the first power supply terminal and a second terminal connected to the voltage source circuit,
The collector terminal of at least one first transistor of the plurality of first transistors is connected to the second terminal of the first resistor via the second resistor. Power amplifier.

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