JP2003051720A - Bias circuit for power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bias circuit with excellent controllability for current control (limit) for a power amplifier at a small power, which can considerably enhance the temperature characteristic of the power amplifier at the small power. SOLUTION: The base of a power bipolar transistor (TR) 2 is connected to the emitter of a bias supply bipolar TR 1 via a resistor 5, the collector of the power control TR 3 is connected to the emitter of the bias supply bipolar TR 1, the emitter of the power control TR 3 is connected to ground via a temperature compensation Schottky diode 19 and a resistor 15, and a power control voltage 13 is applied to the base of the power control TR 3 via a resistor 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bipolar transistor bias circuit for a power amplifier used in mobile communication equipment and the like. In particular, it relates to reduction of current consumption at low output.

[0002]

2. Description of the Related Art In recent years, mobile communication devices typified by mobile phones have rapidly become smaller and have a longer talk time.
For this reason, there is a strong demand for higher efficiency in the transmission power amplifier, which accounts for most of the power consumption during a call.

FIG. 11 is a circuit diagram showing an example of a conventional bias circuit for a power amplifier. In FIG. 11, 1 is a bias supply bipolar transistor, 2 is a power bipolar transistor, 4, 5, 6 and 7 are resistors, 8 and 9 are temperature compensation Schottky diodes, and 10 is a power bipolar transistor 2. A collector current (hereinafter referred to as an idle current), 11 is a Vref voltage that determines the base potential of the bias supply bipolar transistor 1, 12 is a Vcc voltage that gives a potential to the collector of the power bipolar transistor 2, and 20 is a power bipolar transistor 2
It is the base current that flows through.

In the above configuration, the current value of the idle current 10 of the power bipolar transistor 2 is generated by the Vref voltage 11, the bias supply bipolar transistor 1, the resistors 4, 5, 6, 7 and the Schottky diodes 8, 9. Is determined by the base current 20 that is applied.

Next, the structure and operation of the power amplifier having the above power amplifier bias circuit will be described with reference to the drawings. FIG. 12 shows a circuit diagram of an example of the transmission power amplifier. 12, 21 and 22 are shown in FIG.
Bias circuit for power amplifier shown in 23, 24, 2
5 is a high frequency matching circuit, 26 is a high frequency signal input terminal, 27
Is a high frequency signal output terminal.

This power amplifier has a structure having two stages of amplifiers, and the signal input from the high frequency signal input terminal 26 passes through the high frequency matching circuits 23, 24 and 25 and is amplified by the two stages of power amplifiers to obtain high frequency signals. It is output from the signal output terminal 27.

Here, CDMA (Code Division Multip
In recent communication systems represented by le Access), there is a power control function. This is a function (Low Power Mode) of lowering the transmission output of a terminal when a terminal is close to the base station and performing communication with the base station.

At this time, the operation of the power amplifier for transmission is switched from the full power output (about 27.0 dBm) to the low power output (about 15 dBm). At the time of this low power, the transmission power amplifier operates within a range where sufficient linearity is obtained. Therefore, it is possible to lower the bias point (reduce the operating current) while maintaining the linearity. Therefore, in order to improve efficiency in mobile communication terminals, a method of reducing the operating current of the power bipolar transistor 2 by lowering the Vref voltage 11 at the time of low power output is generally used.

[0009]

However, in the bias circuit for the power amplifier shown in FIG. 11, when the operating current of the power bipolar transistor is controlled (limited) by the Vref voltage 11 when the power is low, the Vref is in units of 100 mV. Voltage 11
Need to be controlled (for example, from 2.8 V to 2.7 V), which is difficult to control, and there is a problem that a special circuit or a highly accurate regulator is required outside.

In the conventional power amplifier bias circuit, the Schottky diodes 8 and 9 operate to compensate for the temperature characteristic of the power bipolar transistor 2. However, when the operating current of the power bipolar transistor 2 is controlled (limited) by the Vref voltage 11 when the power is low, the current flowing through the Schottky diodes 8 and 9 is reduced, which causes a problem that the temperature compensation effect is reduced. .

Therefore, the object of the present invention is to solve the above-mentioned problems, and it is excellent in the controllability of the current control (limitation) of the power amplifier at the time of low power, and the temperature characteristic of the power amplifier at the time of low power is greatly improved. It is to provide a bias circuit for a power amplifier which can be improved.

[0012]

In order to achieve the above object, in a bias circuit for a power amplifier according to the present invention, a bias supply bipolar transistor and a base are connected to an emitter of the bias supply bipolar transistor. And a power control bipolar transistor whose collector is connected to the emitter of the bias supply bipolar transistor.

According to this structure, by controlling the base terminal voltage applied to the power control bipolar transistor, it is possible to control (limit) the current when the power is low. The terminal voltage at this time can be controlled by a voltage of several V. Therefore, for example, a digital signal from a control IC that controls the power amplifier can be easily controlled, and the controllability of current control (limitation) of the power amplifier at low power is excellent.

The power amplifier bias circuit according to a second aspect of the present invention is the power amplifier bias circuit according to the first aspect, in which the base and the emitter of the power control bipolar transistor are connected via a resistor. Is characterized by.

According to this structure, in addition to the effect of the power amplifier bias circuit according to the first aspect, the change of the operating current with respect to the base terminal voltage of the power control bipolar transistor can be freely changed by changing the resistance value. It is possible to control, and it is possible to obtain arbitrary current dependence.

The power amplifier bias circuit according to a third aspect of the present invention is the power amplifier bias circuit according to the first aspect, in which the base and collector of the power control bipolar transistor are connected through a resistor. Is characterized by.

According to this structure, in addition to the effect of the power amplifier bias circuit according to the first aspect, the change of the operating current with respect to the base terminal voltage of the power control bipolar transistor can be freely changed by changing the resistance value. It is possible to control, and it is possible to obtain arbitrary current dependence.

A power amplifier bias circuit according to a fourth aspect of the present invention is the power amplifier bias circuit according to the first, second or third aspect, wherein the base of the power control bipolar transistor is grounded through a resistor. It is characterized by being

According to this configuration, the first, second, or third aspect is provided.
In addition to the effect of the bias circuit for a power amplifier described above, it is possible to stabilize the voltage applied to the base of the power control bipolar transistor.

According to a fifth aspect of the present invention, there is provided a power amplifier bias circuit, wherein a bias supply bipolar transistor, a power bipolar transistor whose base is connected to the emitter of the bias supply bipolar transistor, and a collector are bias supply. The bipolar transistor for power control is connected to the emitter of the bipolar transistor, and the bipolar transistor for inverter is connected to the base of the bipolar transistor for power control.

According to this structure, by applying the base terminal voltage to the bipolar transistor for inverter, it acts in the direction of stopping (reducing) the current flowing from the base to the emitter of the bipolar transistor for power control, and the bipolar transistor for power control. The collector current of has a tendency to increase and allows current control (limitation) at low power. The terminal voltage at this time can be controlled by a voltage of several V. Therefore, for example, a digital signal from a control IC that controls the power amplifier can be easily controlled, and the controllability of current control (limitation) of the power amplifier at low power is excellent.

A power amplifier bias circuit according to a sixth aspect of the present invention is the power amplifier bias circuit according to the first, second, third or fourth aspect, wherein the base of the power controlling bipolar transistor is a bias supplying bipolar transistor. It is connected to the base of.

According to this configuration, in addition to the effect of the power amplifier bias circuit according to the first, second, third, or fourth aspect, a constant voltage is always applied to the base of the power control bipolar transistor. Therefore, as compared with the invention described in claim 1, 2, 3 or 4, the transistor operates even when the voltage applied to the base terminal of the power control bipolar transistor is low, and the collector current of the bias supply bipolar transistor is reduced. The effect of

A bias circuit for a power amplifier according to a seventh aspect of the present invention is the bias circuit for a power amplifier according to the first aspect, wherein a PN diode is connected to the emitter of the power control bipolar transistor. It is characterized by being.

According to this structure, when a voltage is applied to the base of the power control bipolar transistor to reduce the current, the PN diode exerts a temperature compensating function for compensating the temperature characteristic variation of the power bipolar transistor. Is obtained.

The power amplifier bias circuit according to the present invention is the power amplifier bias circuit according to any one of claims 1, 2, 3, 4 or 6, wherein a Schottky diode is provided at the emitter of the power control bipolar transistor. It is characterized by being connected.

According to this structure, when a voltage is applied to the base of the power control bipolar transistor to reduce the current, the Schottky diode exerts a stronger temperature compensation function as compared with the invention of claim 7. Is obtained.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram showing a first embodiment of a bias circuit for a power amplifier according to the present invention. In FIG. 1, 1 is a bias supply bipolar transistor, 2 is a power bipolar transistor, 3 is a power control bipolar transistor, 4,
5, 6, 7, 14, and 15 are resistors, 8 and 9 are Schottky diodes, 10 is an idle current, and 11 is Vr that determines the base potential of the bias supply bipolar transistor 1.
ef voltage, 12 is a Vcc voltage that gives a potential to the collector of the power bipolar transistor, 13 is a power control voltage, 28
Is the base current of the power bipolar transistor 2, 29
Is the collector current of the power control bipolar transistor 3.

This power amplifier bias circuit is shown in FIG.
The following configuration is added to the power amplifier bias circuit of the related art. That is, the power control bipolar transistor 3 and the resistors 14 and 15 are newly added to the emitter of the bias supply bipolar transistor 1, and the power control voltage 13 is applied to the base of the power control bipolar transistor 3 via the resistor 14. ing. With this configuration, it is possible to reduce the idle current 10 at the time of low power by applying the power control voltage 13.

According to this structure, the power control bipolar transistor 3 is operated by applying the power control voltage 13 when the power is low. As a result, the collector current 29 of the power control bipolar transistor 3 flows.
Therefore, the base current 28 of the power bipolar transistor 2 decreases and the idle current 10 decreases.

FIG. 2 shows the power control voltage 1 of the first embodiment.
The dependence of the idle current 10 on 3 is shown by the solid line A1. The vertical axis of FIG. 2 is the idle current (mA), and the horizontal axis is the power control voltage (V). Further, the dependency of the idle current 10 on the Vref voltage 11 in the conventional example of FIG. 11 is shown by a dotted line A2. It can be seen from FIG. 2 that the idle current 10 is reduced by applying the power control voltage 13. here,
It should be noted that the control method of the first embodiment shown by the solid line A1 has a gentle voltage dependency as compared with the method of controlling by the Vref voltage 11 shown by the dotted line A2 as in the conventional example, so that the controllability is low. It turns out that it is excellent. That is, it becomes possible to control the idle current 10 at a voltage of several V. For this reason,
The first embodiment of the present invention has an advantage that a special circuit and a highly accurate regulator are not required outside.

In the conventional example, since the bias supply bipolar transistor 1 and the power bipolar transistor 2 have a two-stage amplifier structure, a change in the base voltage value of the bias supply bipolar transistor is amplified by two stages. The idle current changes greatly. That is, the voltage dependency becomes steep in the conventional example.

In the control method of the first embodiment shown by the solid line A1, the idle current 10 is stabilized at a low current value in the vicinity of about 3 V, and the power control bipolar transistor is applied from the terminal to which the power control voltage 13 is applied. Even if the current flowing to the base of 3 is low, the power control bipolar transistor 3 can be sufficiently driven, so that it can be easily controlled by a digital signal from a control IC for controlling the power amplifier, for example. That is, the digital signal can be used as it is as the power control voltage 13.

According to this embodiment, current control at low power is possible by controlling the base terminal voltage of the power control bipolar transistor 3, and the terminal voltage at this time is controlled by a voltage of several V units. can do. Therefore, it is possible to easily control even a digital signal from a control IC that controls the power amplifier, for example, and the controllability of current control (limitation) at low power is excellent.

Since the base of the power controlling bipolar transistor 3 is grounded via the resistor 14, the voltage applied to the base of the power controlling bipolar transistor 3 can be stabilized.

(Second Embodiment) FIG. 3 is a circuit diagram showing a second embodiment of the bias circuit for power amplifier of the present invention.

The second embodiment shown in FIG. 3 is different from the first embodiment shown in FIG. 1 in that a resistor 16 is added between the collector and the base of the power control bipolar transistor 3 and a resistor is provided between the emitter and the base. 17 is added.

As described above, the base and collector of the power control bipolar transistor 3 are connected via the resistor 16, so that the resistance 16 can be prevented from changing the idle current 10 with respect to the base terminal voltage of the power control bipolar transistor 3. It is possible to control freely by changing the value of, and it is possible to obtain arbitrary current dependence.

Similarly, since the base and emitter of the power control bipolar transistor 3 are connected via the resistor 17, the power control bipolar transistor 3 is connected.
The change of the idle current 10 with respect to the base terminal voltage of
It is possible to control freely by changing the value of the resistor 17, and it is possible to obtain arbitrary current dependency.

In order to explain the features of the second embodiment,
In FIG. 4, the dependency of the idle current 10 on the power control voltage 13 of the first embodiment is shown by the solid line B1. Also, the second
In the power amplifier bias circuit of the embodiment, the dependency of the idle current 10 on the power control voltage 13 when the resistor 16 is added is shown by a broken line B2. Also, the second
In the power amplifier bias circuit of the embodiment, the dependency of the idle current 10 on the power control voltage 13 when the resistor 17 is added is shown by a dotted line B3. Furthermore, in the bias circuit for the power amplifier of the second embodiment,
The dependency of the idle current 10 on the power control voltage 13 when both the resistors 16 and 17 are added is shown by a dashed line B4.
Indicate.

It can be seen from FIG. 4 that the voltage at which the reduction of the idle current 10 starts is increased by adding the resistor 17. Further, it can be seen that the voltage at which the idle current 10 stably starts on the low current value side increases by adding the resistor 16. The addition of the resistor 16 increases the voltage at which the idle current 10 stably starts at a low current value because the addition of the resistor 16 reduces the dependence of the idle current 10 on the power control voltage 13. Is.

Here, the reason why the dependence of the idle current 10 on the power control voltage 13 is changed by adding the resistors 16 and 17 will be described.

When the resistor 17 is added, the voltage applied to the base of the power control bipolar transistor 3 is
A voltage determined by the distribution ratio between the resistor 14 and the resistors 17 and 15 is applied. Therefore, since a voltage lower than the power control voltage 13 is applied to the power control bipolar transistor 3, the dependency of the idle current 10 shown in FIG. 4 is substantially parallel to the high voltage side (to the right) with respect to the solid line B1. It becomes a shifted shape.

When the resistor 16 is added, a voltage determined by the distribution ratio of the resistor 14 and the resistor 16 is applied to the base of the power control bipolar transistor 3.
Therefore, the base voltage of the power control bipolar transistor 3 changes gently with respect to the change of the power control voltage 13. At this time, the base voltage of the power bipolar transistor 2 to which the resistor 16 is connected is higher than the threshold voltage of the transistor.
The threshold voltage does not change. Therefore, the dependency of the idle current in FIG. 4 becomes gentler as indicated by the broken line B2 as compared with the solid line B1.

Further, when both the resistors 16 and 17 are added, the voltage at which the reduction of the idle current 10 starts is increased and the idle current 1 is increased as shown by the chain line B4.
The dependency of 0 becomes loose.

FIG. 13 shows the dependence of the base voltage of the power control transistor 3 on the power control voltage 13. FIG.
In, the solid line F1 indicates the dependence of the base voltage of the power control transistor 3 on the power control voltage 13 of the first embodiment. The dotted line F2 shows the dependence of the base voltage of the power control transistor 3 on the power control voltage 13 when the resistor 17 is added in the power amplifier bias circuit of the second embodiment. The broken line F3 shows the dependence of the base voltage of the power control transistor 3 on the power control voltage 13 when the resistor 16 is added in the power amplifier bias circuit of the second embodiment. A thick solid line F4 indicates the threshold voltage of the transistor.

With this configuration, it is possible to freely control the change of the idle current with respect to the power control voltage 13, and it is possible to obtain an arbitrary current dependency. For example, when controlling the idle current 10 in several stages,
By reducing the resistance 17, the dependence of the idle current 10 on the power control voltage 13 is moderated, and the controllability is improved.

(Third Embodiment) FIG. 5 is a circuit diagram showing a third embodiment of the power amplifier bias circuit of the present invention. The third embodiment shown in FIG. 5 corresponds to the first embodiment shown in FIG.
In contrast to the embodiment described above, the bipolar transistor 3 for inverter is added to the base of the bipolar transistor 3 for power control.
0 is connected, the power control voltage 13 is applied to the base of the inverter bipolar transistor 30 via the resistor 14, the emitter of the inverter bipolar transistor 30 is grounded via the resistor 31, and the inverter bipolar transistor 30 is connected. The Vcc voltage 12 is applied to the collector of the transistor through the resistor 32. Other configurations are similar to those of the embodiment shown in FIG.

In order to explain the features of the third embodiment,
In FIG. 6, the dependency of the idle current 10 on the power control voltage 13 of the first embodiment is shown by a dotted line C1. Also, the third
The solid line C2 shows the dependency of the idle current 10 on the power control voltage 13 in the embodiment. It can be seen from FIG. 6 that the idle current 10 can be controlled (limited) by lowering the power control voltage 13 contrary to the first embodiment.

According to this embodiment, by applying the base terminal voltage to inverter bipolar transistor 30, the base voltage of power control bipolar transistor 3 is lowered by the operation of inverter bipolar transistor 30. Therefore, the current flowing from the collector to the emitter of the power control bipolar transistor 3 acts in a direction to stop (reduce) the current, so that the collector current of the power bipolar transistor 2 tends to increase. At this time, by controlling the collector terminal voltage of the power control bipolar transistor 3, it is possible to control the current at low power, and the terminal voltage at this time can be controlled by a voltage of several V unit. Therefore, for example, a control IC for controlling the power amplifier
It is possible to easily control even with a digital signal from, and the controllability of current control (limitation) at low power is excellent.

(Fourth Embodiment) FIG. 7 is a circuit diagram showing a fourth embodiment of the power amplifier bias circuit of the present invention. The fourth embodiment shown in FIG. 7 corresponds to the first embodiment shown in FIG.
The embodiment is characterized in that the base of the power controlling bipolar transistor 3 is connected to the Vref voltage 11 via the resistor 18.

In order to explain the features of the fourth embodiment,
In FIG. 8, the dependency of the idle current 10 on the power control voltage 13 of the first embodiment is shown by a broken line D1, and the dependency of the idle current 10 on the power control voltage 13 of the fourth embodiment is shown by a solid line D2. .

From FIG. 8, it is possible to control the idle current 10 with a low power control voltage 13 as compared with the first embodiment. That is, as compared with the first embodiment, the Vref voltage 11 is always applied to the base of the power control bipolar transistor 3.
Since the current is already supplied to the power control bipolar transistor 3 at the Vref voltage 11, the power control bipolar transistor 3 operates at a voltage at which the power control voltage 13 is lower than the threshold value of the power control bipolar transistor 3. And power bipolar transistor 2
Collector current is reduced.

Others are the same as those in the first embodiment.
The configuration in which the base of the power control bipolar transistor 3 is connected to the Vref voltage 11 via the resistor 18 is shown in FIG.
The present invention can be applied to the above embodiment, and the same effect can be obtained in that case.

(Fifth Embodiment) FIG. 9 is a circuit diagram showing a fifth embodiment of the power amplifier bias circuit of the present invention. The fifth embodiment shown in FIG. 9 corresponds to the first embodiment shown in FIG.
In contrast to the embodiment described above, the Schottky diode 19 is connected to the emitter of the power control bipolar transistor 3. As a result, when the idle current 10 is reduced by applying the power control voltage 13, the Schottky diode 19 acts to cancel the temperature characteristic of the power bipolar transistor 2 and reduces the temperature change of the idle current 10. The action is obtained.

In order to explain the features of the fifth embodiment,
FIG. 10 shows the temperature dependence of the idle current. Here, the broken line E1 is the temperature dependence without current control, and the dotted line E1 is
2 shows the temperature dependence during the idle current control by the Vref voltage in the conventional example of FIG. 2, and the solid line E3 shows the temperature dependence during the idle current control in the fifth embodiment. Dashed line E1
When the current control shown in is not performed, the temperature change of the idle current 10 is reduced by the temperature compensation effect of the Schottky diodes 8 and 9 and the power bipolar transistor 2.

However, when the idle current is controlled by the Vref voltage 11 shown by the dotted line E2, the temperature compensation balance is lost, and the idle current 10 tends to increase at high temperatures.

Therefore, according to the fifth embodiment shown by the solid line E3, the Schottky diode 19 also works so as to cancel the temperature characteristic of the power bipolar transistor 2, so that the temperature change of the idle current 10 as compared with the conventional example. Can be significantly improved. Other effects are similar to those of the embodiment shown in FIG. The configuration in which the Schottky diode 19 is connected can be applied to the embodiment of FIG. 3, and the same effect can be obtained in that case as well.

Also, when a PN diode is used instead of the Schottky diode 19, the compensation amount is slightly reduced, but the temperature compensation effect is also obtained.

[0061]

According to the power amplifier bias circuit of the present invention, it is possible to greatly improve the controllability of the current control of the power amplifier when the power is low.

If a PN diode or a Schottky diode is connected to the emitter of the power control bipolar transistor to have a temperature compensating function at low power, the temperature characteristic of the power amplifier at low power is greatly improved. be able to.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a power amplifier bias circuit according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing power control voltage-idle current characteristics of the power amplifier bias circuit according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a power amplifier bias circuit according to a second embodiment of the present invention.

FIG. 4 is a characteristic diagram showing power control voltage-idle current characteristics of a bias circuit for a power amplifier according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a power amplifier bias circuit according to a third embodiment of the present invention.

FIG. 6 is a characteristic diagram showing power control voltage-idle current characteristics of a bias circuit for a power amplifier according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a power amplifier bias circuit according to a fourth embodiment of the present invention.

FIG. 8 is a characteristic diagram showing power control voltage-idle current characteristics of a bias circuit for a power amplifier according to a fourth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a power amplifier bias circuit according to a fifth embodiment of the present invention.

FIG. 10 is a characteristic diagram showing an idle current-temperature characteristic of a power amplifier bias circuit according to a fifth embodiment of the present invention.

FIG. 11 is a circuit diagram showing a configuration of a power amplifier bias circuit in a conventional example.

FIG. 12 is a circuit diagram showing a configuration of a transmission power amplifier in a conventional example.

FIG. 13 is a characteristic diagram showing the dependence of the base voltage of the power control transistor on the power control voltage.

[Explanation of symbols]

1 Bias supply bipolar transistor 2 Power bipolar transistor 3 Power control bipolar transistor 4, 5, 6, 7, 14, 16, 17, 18 Schottky diode 8, 9, 19 Schottky diode 7 Vcc voltage 8 Power control Bipolar transistor 10 Idle current 11 Vref voltage 12 Vcc voltage 13 Power control voltage

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5J090 AA01 AA41 CA02 CA36 CN02                       FA10 FN06 HA02 HA19 HA25                       KA11 KA12 KA29 KA47 MA21                       SA14 TA02                 5J091 AA01 AA41 CA02 CA36 FA10                       HA02 HA19 HA25 KA11 KA12                       KA29 KA47 MA21 SA14 TA02                       UW08                 5J092 AA01 AA41 CA02 CA36 FA10                       GR09 HA02 HA19 HA25 KA11                       KA12 KA29 KA47 MA21 SA14                       TA02

Claims (8)

[Claims] 1. A bias supply bipolar transistor, a power bipolar transistor whose base is connected to the emitter of the bias supply bipolar transistor, and a power control bipolar transistor whose collector is connected to the emitter of the bias supply bipolar transistor. A bias circuit for a power amplifier including a transistor. 2. A bias supply bipolar transistor, a power bipolar transistor whose base is connected to the emitter of the bias supply bipolar transistor, and a power control bipolar transistor whose collector is connected to the emitter of the bias supply bipolar transistor. A bias circuit for a power amplifier, comprising: a transistor, wherein a base and an emitter of the power control bipolar transistor are connected via a resistor. 3. A bias supply bipolar transistor, a power bipolar transistor whose base is connected to the emitter of the bias supply bipolar transistor, and a power control bipolar transistor whose collector is connected to the emitter of the bias supply bipolar transistor. A bias circuit for a power amplifier, comprising a transistor, wherein the base and collector of the power control bipolar transistor are connected via a resistor. 4. The power amplifier bias circuit according to claim 1, wherein the base of the power control bipolar transistor is grounded through a resistor. 5. A bipolar transistor for bias supply, a power bipolar transistor whose base is connected to the emitter of the bipolar transistor for bias supply, and a bipolar transistor for power control whose collector is connected to the emitter of the bipolar transistor for bias supply. A bias circuit for a power amplifier, comprising a transistor and an inverter bipolar transistor whose collector is connected to the base of the power control bipolar transistor. 6. The base of the power controlling bipolar transistor is connected to the base of the bias supplying bipolar transistor.
The bias circuit for a power amplifier according to 2, 3, or 4. 7. The bias circuit for a power amplifier according to claim 1, wherein a PN diode is connected to an emitter of the power control bipolar transistor. 8. The bias circuit for a power amplifier according to claim 1, wherein a Schottky diode is connected to an emitter of the power control bipolar transistor.