U.S. patent application number 15/184035 was filed with the patent office on 2017-01-19 for power amplification module.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Masatoshi Hase.
Application Number | 20170019081 15/184035 |
Document ID | / |
Family ID | 57748972 |
Filed Date | 2017-01-19 |
United States Patent
Application |
20170019081 |
Kind Code |
A1 |
Hase; Masatoshi |
January 19, 2017 |
POWER AMPLIFICATION MODULE
Abstract
A power amplification module includes: a first bipolar
transistor in which a radio frequency signal is input to a base and
an amplified signal is output from a collector; a second bipolar
transistor that is thermally coupled with the first bipolar
transistor and that imitates operation of the first bipolar
transistor; a third bipolar transistor in which a first control
voltage is supplied to a base and a first bias current is output
from an emitter; a first resistor that generates a third control
voltage corresponding to a collector current of the second bipolar
transistor at a second terminal; and a fourth bipolar transistor in
which a power supply voltage is supplied to a collector, the third
control voltage is supplied to a base, and a second bias current is
output from an emitter.
Inventors: |
Hase; Masatoshi; (Kyoto,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Kyoto |
|
JP |
|
|
Family ID: |
57748972 |
Appl. No.: |
15/184035 |
Filed: |
June 16, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03F 3/19 20130101; H03F
3/195 20130101; H01L 23/66 20130101; H03F 3/24 20130101; H04W 88/02
20130101; H03F 3/191 20130101; H01L 29/0804 20130101; H03F 1/302
20130101; H03F 2200/451 20130101; H01L 29/737 20130101; H03F 3/245
20130101; H03F 2200/18 20130101; H03F 2200/447 20130101; H04B
2001/0408 20130101; H03F 2200/555 20130101; H03G 3/3042
20130101 |
International
Class: |
H03G 3/30 20060101
H03G003/30; H01L 29/08 20060101 H01L029/08; H03F 3/24 20060101
H03F003/24; H01L 27/06 20060101 H01L027/06; H03F 3/19 20060101
H03F003/19; H01L 23/66 20060101 H01L023/66; H01L 29/737 20060101
H01L029/737 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2015 |
JP |
2015-141429 |
Claims
1. A power amplification module comprising: a first bipolar
transistor, wherein when a radio frequency signal is input to a
base of the first bipolar transistor, the first bipolar transistor
outputs from a collector of the first bipolar transistor an
amplified signal obtained by amplifying the radio frequency signal;
a second bipolar transistor that is thermally coupled with the
first bipolar transistor, wherein when the radio frequency signal
is input to a base of the second bipolar transistor, the second
bipolar transistor imitates operation of the first bipolar
transistor; a third bipolar transistor, wherein when a power supply
voltage is supplied to a collector of the third bipolar transistor
and a first control voltage is supplied to a base of the third
bipolar transistor, the third bipolar transistor outputs a first
bias current from an emitter of the third bipolar transistor to the
base of the first bipolar transistor and the base of the second
bipolar transistor; a first resistor, wherein when a second control
voltage is supplied to a first terminal of the first resistor and a
second terminal of the first resistor is connected to a collector
of the second bipolar transistor, the first resistor generates a
third control voltage at the second terminal of the first resistor,
the third control voltage corresponding to a collector current of
the second bipolar transistor; and a fourth bipolar transistor,
wherein when the power supply voltage is supplied to a collector of
the fourth bipolar transistor and the third control voltage is
supplied to a base of the fourth bipolar transistor, the fourth
bipolar transistor outputs a second bias current from an emitter of
the fourth bipolar transistor to the base of the first bipolar
transistor and the base of the second bipolar transistor.
2. The power amplification module according to claim 1, wherein an
emitter area of the second bipolar transistor is smaller than an
emitter area of the first bipolar transistor.
3. The power amplification module according to claim 1, further
comprising: a second resistor, wherein a first terminal of the
second resistor is connected to the emitter of the third bipolar
transistor and the emitter of the fourth bipolar transistor, and a
second terminal of the second resistor is connected to the base of
the first bipolar transistor; and a third resistor, wherein a first
terminal of the third resistor is connected to the emitter of the
third bipolar transistor and the emitter of the fourth bipolar
transistor, and a second terminal of the third resistor is
connected to the base of the second bipolar transistor; wherein the
radio frequency signal is supplied to a point between the second
terminal of the second resistor and the base of the first bipolar
transistor and to a point between the second terminal of the third
resistor and the base of the second bipolar transistor.
4. The power amplification module according to claim 1, further
comprising: a fourth resistor, wherein a first terminal of the
fourth resistor is connected to the emitter of the third bipolar
transistor and the emitter of the fourth bipolar transistor and a
second terminal of the fourth resistor is connected to the base of
the first bipolar transistor and the base of the second bipolar
transistor; wherein the radio frequency signal is supplied to a
point between the second terminal of the fourth resistor and the
base of the first bipolar transistor and the base of the second
bipolar transistor.
5. The power amplification module according to claim 4, further
comprising: a first capacitor, wherein the radio frequency signal
is input to the base of the first bipolar transistor and the base
of the second bipolar transistor via the first capacitor.
6. The power amplification module according to claim 1, further
comprising: a fifth resistor; a fifth bipolar transistor; and a
sixth bipolar transistor; wherein a fourth control voltage is
supplied to a first terminal of the fifth resistor and a second
terminal of the fifth resistor is connected to a collector of the
fifth bipolar transistor, a base and the collector of the fifth
bipolar transistor are connected to each other and an emitter of
the fifth bipolar transistor is connected to a collector of the
sixth bipolar transistor, a base and the collector of the sixth
bipolar transistor are connected to each other and an emitter of
the sixth bipolar transistor is grounded, the first bipolar
transistor and the sixth bipolar transistor are thermally coupled
with each other, and the first control voltage is output from the
base of the fifth bipolar transistor.
7. The power amplification module according to claim 6, further
comprising: a seventh bipolar transistor, wherein a collector of
the seventh bipolar transistor is connected to the emitter of the
third bipolar transistor and the emitter of the fourth bipolar
transistor, a base of the seventh bipolar transistor is connected
to the base of the sixth bipolar transistor, and an emitter of the
seventh bipolar transistor is grounded.
8. The power amplification module according to claim 7, further
comprising: a sixth resistor that is provided between the base of
the sixth bipolar transistor and the base of the seventh bipolar
transistor.
9. The power amplification module according to claim 7, wherein the
first bipolar transistor and the seventh bipolar transistor are
thermally coupled with each other.
10. The power amplification module according to claim 5, further
comprising: a fifth resistor; a fifth bipolar transistor; and a
sixth bipolar transistor; wherein a fourth control voltage is
supplied to a first terminal of the fifth resistor and a second
terminal of the fifth resistor is connected to a collector of the
fifth bipolar transistor, a base and the collector of the fifth
bipolar transistor are connected to each other and an emitter of
the fifth bipolar transistor is connected to a collector of the
sixth bipolar transistor, a base and the collector of the sixth
bipolar transistor are connected to each other and an emitter of
the sixth bipolar transistor is grounded, the first bipolar
transistor and the sixth bipolar transistor are thermally coupled
with each other, and the first control voltage is output from the
base of the fifth bipolar transistor.
11. A power amplification module comprising: a first bipolar
transistor, wherein when a radio frequency signal is input to a
base of the first bipolar transistor, the first bipolar transistor
outputs from a collector of the first bipolar transistor an
amplified signal obtained by amplifying the radio frequency signal;
a second bipolar transistor that is thermally coupled with the
first bipolar transistor, wherein when the radio frequency signal
is input to a base of the second bipolar transistor, the second
bipolar transistor imitates operation of the first bipolar
transistor; a first field effect transistor, wherein when a power
supply voltage is supplied to a drain of the first field effect
transistor and a first control voltage is supplied to a gate of the
first field effect transistor, the first field effect transistor
outputs a first bias current from a source of the first field
effect transistor to the base of the first bipolar transistor and
the base of the second bipolar transistor; a first resistor,
wherein when a second control voltage is supplied to a first
terminal of the first resistor and a second terminal of the first
resistor is connected to a collector of the second bipolar
transistor, the first resistor generates a third control voltage at
the second terminal of the first resistor, the third control
voltage corresponding to a collector current of the second bipolar
transistor; and a second field effect transistor, wherein when the
power supply voltage is supplied to a drain of the second field
effect transistor and the third control voltage is supplied to a
gate of the second field effect transistor, the second field effect
transistor outputs a second bias current from a source of the
second field effect transistor to the base of the first bipolar
transistor and the base of the second bipolar transistor.
12. The power amplification module according to claim 11, wherein
an emitter area of the second bipolar transistor is smaller than an
emitter area of the first bipolar transistor.
13. The power amplification module according to claim 11, further
comprising: a second resistor, wherein a first terminal of the
second resistor is connected to the source of the first field
effect transistor and the source of the second field effect
transistor, and a second terminal of the second resistor is
connected to the base of the first bipolar transistor; and a third
resistor, wherein a first terminal of the third resistor is
connected to the source of the first field effect transistor and
the source of the second field effect transistor, and a second
terminal of the third resistor is connected to the base of the
second bipolar transistor; wherein the radio frequency signal is
supplied to a point between the second terminal of the second
resistor and the base of the first bipolar transistor and to a
point between the second terminal of the third resistor and the
base of the second bipolar transistor.
14. The power amplification module according to claim 11, further
comprising: a fourth resistor, wherein a first terminal of the
fourth resistor is connected to the source of the first field
effect transistor and the source of the second field effect
transistor and a second terminal of the fourth resistor is
connected to the base of the first bipolar transistor and the base
of the second bipolar transistor; wherein the radio frequency
signal is supplied to a point between the second terminal of the
fourth resistor and the base of the first bipolar transistor and
the base of the second bipolar transistor.
15. The power amplification module according to claim 14, further
comprising: a first capacitor, wherein the radio frequency signal
is input to the base of the first bipolar transistor and the base
of the second bipolar transistor via the first capacitor.
16. The power amplification module according to claim 11, further
comprising: a fifth resistor; a third field effect transistor; and
a sixth bipolar transistor; wherein a fourth control voltage is
supplied to a first terminal of the fifth resistor and a second
terminal of the fifth resistor is connected to a drain of the third
field effect transistor, a gate and the drain of the third field
effect transistor are connected to each other and a source of the
third field effect transistor is connected to a collector of the
sixth bipolar transistor, a base and the collector of the sixth
bipolar transistor are connected to each other and an emitter of
the sixth bipolar transistor is grounded, the first bipolar
transistor and the sixth bipolar transistor are thermally coupled
with each other, and the first control voltage is output from the
gate of the third field effect transistor.
17. The power amplification module according to claim 16, further
comprising: a seventh bipolar transistor, wherein a collector of
the seventh bipolar transistor is connected to the source of the
third field effect transistor and the source of the second field
effect transistor, a base of the seventh bipolar transistor is
connected to the base of the sixth bipolar transistor, and an
emitter of the seventh bipolar transistor is grounded.
18. The power amplification module according to claim 17, further
comprising: a sixth resistor that is provided between the base of
the sixth bipolar transistor and the base of the seventh bipolar
transistor.
19. The power amplification module according to claim 17, wherein
the first bipolar transistor and the seventh bipolar transistor are
thermally coupled with each other.
20. The power amplification module according to claim 15, further
comprising: a fifth resistor; a third field effect transistor; and
a sixth bipolar transistor; wherein a fourth control voltage is
supplied to a first terminal of the fifth resistor and a second
terminal of the fifth resistor is connected to a drain of the third
field effect transistor, a gate and the drain of the third field
effect transistor are connected to each other and a source of the
third field effect transistor is connected to a collector of the
sixth bipolar transistor, a base and the collector of the sixth
bipolar transistor are connected to each other and an emitter of
the sixth bipolar transistor is grounded, the first bipolar
transistor and the sixth bipolar transistor are thermally coupled
with each other, and the first control voltage is output from the
gate of the third field effect transistor.
Description
BACKGROUND
[0001] The present disclosure relates to a power amplification
module.
[0002] The second generation mobile communication system (2G) and
the third/fourth generation mobile communication system (3G/4G) are
examples of wireless communication schemes used in mobile
terminals. In 2G, it is required that the power of a radio
frequency (RF) signal be changed in accordance with the waveform
characteristics, which are stipulated by the standard, at the time
of a burst operation in which data is continuously transmitted from
a mobile terminal. In addition, a power amplification module, which
is for amplifying the power of an RF signal, is used in a mobile
terminal in order to transmit the RF signal to a base station.
Therefore, it is required that gain variations be suppressed in the
power amplification module in order to output an RF signal in
accordance with the waveform characteristics stipulated by the
standard.
[0003] For example, a radio frequency amplifier that aims to
suppress gain variations that occur with changes in temperature is
disclosed in FIG. 3 of Japanese Unexamined Patent Application
Publication No. 11-330866. This radio frequency amplifier includes
a power transistor Q1 and a control transistor Qc having a size of
1/m of that of the power transistor Q1. An RF signal input to the
base of the power transistor Q1 is input to the base of the control
transistor Qc via a resistor Rb/m and a resistor Rb. Changes that
occur in the collector current of the power transistor Q1 with
changes in temperature and so forth are reflected in the collector
current of the control transistor Qc. A bias current supplied to
the base of the power transistor Q1 is controlled and gain
variations are suppressed by controlling a differential amplifier
in accordance with changes in the collector current of the control
transistor Qc.
[0004] As described above, the bias current is controlled by using
a differential amplifier in order to suppress gain variations that
occur with changes in temperature in the configuration disclosed in
Japanese Unexamined Patent Application Publication No. 11-330866.
Consequently, the circuit scale is increased.
BRIEF SUMMARY
[0005] The present disclosure provides a power amplification module
that can suppress gain variations that occur with changes in
temperature without necessarily increasing the circuit scale.
[0006] A power amplification module according to an embodiment of
the present disclosure includes: a first bipolar transistor that
has a radio frequency signal input to a base thereof and that
outputs from a collector thereof an amplified signal obtained by
amplifying the radio frequency signal; a second bipolar transistor
that is thermally coupled with the first bipolar transistor, that
has the radio frequency signal input to a base thereof, and that
imitates operation of the first bipolar transistor; a third bipolar
transistor that has a power supply voltage supplied to a collector
thereof, that has a first control voltage supplied to a base
thereof and that outputs a first bias current from an emitter
thereof to the bases of the first and second bipolar transistors; a
first resistor that has a second control voltage supplied to a
first terminal thereof, that has a second terminal thereof
connected to a collector of the second bipolar transistor and that
generates a third control voltage at the second terminal thereof,
the third control voltage corresponding to a collector current of
the second bipolar transistor; and a fourth bipolar transistor that
has the power supply voltage supplied to a collector thereof, that
has the third control voltage supplied to a base thereof and that
outputs a second bias current from an emitter thereof to the bases
of the first and second bipolar transistors.
[0007] According to the embodiment of the present disclosure, a
power amplification module can be provided that can suppress gain
variations that that occur with changes in temperature and that can
suppress an increase in circuit scale.
[0008] Other features, elements, characteristics and advantages of
the present disclosure will become more apparent from the following
detailed description of embodiments of the present disclosure with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] FIG. 1 illustrates an example configuration of a
transmission unit that includes a power amplification module
according to an embodiment of the present disclosure;
[0010] FIG. 2 illustrates an example configuration of the power
amplification module;
[0011] FIG. 3 illustrates configurations of an amplification
circuit and a bias circuit, which are example configurations of the
amplification circuit and the bias circuit illustrated in FIG.
2;
[0012] FIG. 4 illustrates the configuration of a comparative
example, which is for comparison with the embodiment;
[0013] FIG. 5 illustrates simulation results for the comparative
example illustrated in FIG. 4;
[0014] FIG. 6 illustrates simulation results for the amplification
circuit and the bias circuit of the embodiment;
[0015] FIG. 7 illustrates configurations of an amplification
circuit and a bias circuit, which are example configurations of the
amplification circuit and the bias circuit illustrated in FIG.
2;
[0016] FIG. 8 illustrates configurations of an amplification
circuit and a bias circuit, which are example configurations of the
amplification circuit and the bias circuit illustrated in FIG. 2;
and
[0017] FIG. 9 illustrates configurations of an amplification
circuit and a bias circuit, which are example configurations of the
amplification circuit and the bias circuit illustrated in FIG.
2.
DETAILED DESCRIPTION
[0018] Hereafter, embodiments of the present disclosure will be
described while referring to the drawings. FIG. 1 illustrates an
example configuration of a transmission unit that includes a power
amplification module according to an embodiment of the present
disclosure. A transmission unit 100 is for example used in a mobile
communication device such as a cellular phone in order to transmit
various signals such as speech and data to a base station. Although
such a mobile communication device would also be equipped with a
reception unit for receiving signals from the base station, the
description of such a reception unit is omitted here.
[0019] As illustrated in FIG. 1, the transmission unit 100 includes
a base band unit 110, an RF unit 111, a power amplification module
112, a front end unit 113 and an antenna 114.
[0020] The base band unit 110 modulates an input signal such as
speech or data and outputs a modulated signal. In this embodiment,
the modulated signal output from the base band unit 110 is output
as IQ signals (I signal and Q signal) with the amplitude and the
phase being represented on an IQ plane. The frequencies of the IQ
signals are on the order of several MHz to several tens of MHz, for
example. In addition, the base band unit 110 outputs a mode signal
MODE that is for controlling the gain in the power amplification
module 112.
[0021] The RF unit 111 generates an RF signal (RF.sub.IN), which is
for performing wireless transmission, from the IQ signals output
from the base band unit 110. The RF signal has a frequency of
around several hundred MHz to several GHz, for example. In the RF
unit 111, the IQ signals may be converted into an intermediate
frequency (IF) signal and an RF signal may be then generated from
the IF signal, instead of directly converting the IQ signals into
the RF signal.
[0022] The power amplification module 112 amplifies the power of
the RF signal (RF.sub.IN) output from the RF unit 111 up to the
level that is required to transmit the RF signal to the base
station, and outputs an amplified signal (RF.sub.OUT). In the power
amplification module 112, the size of a bias current is determined
and the gain is controlled on the basis of the mode signal MODE
supplied from the base band unit 110.
[0023] The front end unit 113 performs filtering on the amplified
signal (RF.sub.OUT) and switching on a reception signal received
from the base station. The amplified signal output from the front
end unit 113 is transmitted to the base station via the antenna
114.
[0024] FIG. 2 illustrates an example configuration of the power
amplification module 112. As illustrated in FIG. 2, the power
amplification module 112 includes an amplification circuit 200, an
inductor 210, a bias control circuit 220 and a bias circuit
230.
[0025] The amplification circuit 200 amplifies the RF signal
(RF.sub.IN) and outputs an amplified signal (RF.sub.OUT). The
number of stages of the amplification circuit is not limited to one
and may be two or more.
[0026] The inductor 210 is provided in order to isolate the RF
signal. A power supply voltage V.sub.CC is supplied to the
amplification circuit 200 via the inductor 210.
[0027] The bias control circuit 220 outputs control voltages
V.sub.1 and V.sub.2, which are for controlling a bias current
I.sub.BIAS, on the basis of the mode signal MODE.
[0028] The bias circuit 230 supplies the bias current I.sub.BIAS to
the amplification circuit 200. The size of the bias current output
from the bias circuit 230 is controlled by the control voltages
V.sub.1 and V.sub.2.
[0029] FIG. 3 illustrates configurations of an amplification
circuit 200A and a bias circuit 230A, which are example
configurations of the amplification circuit 200 and the bias
circuit 230 illustrated in FIG. 2.
[0030] The amplification circuit 200A includes a bipolar transistor
300, a capacitor 301 and a resistor 302. The bipolar transistor 300
(first bipolar transistor) is a heterojunction bipolar transistor
(HBT), for example. The RF signal (RF.sub.IN) is input to the base
of the bipolar transistor 300 via the capacitor 301. The power
supply voltage V.sub.CC is supplied to the collector of the bipolar
transistor 300 via the inductor 210. The emitter of the bipolar
transistor 300 is grounded. In addition, the bias current is
supplied to the base of the bipolar transistor 300 via the resistor
302 (second resistor). The amplified signal (RF.sub.OUT) is output
from the collector of the bipolar transistor 300.
[0031] The bias circuit 230A includes bipolar transistors 310, 311,
312, 313 and 314, capacitors 320 and 321 and resistors 330, 331,
332 and 333. The bipolar transistors 310 to 314 are HBTs, for
example.
[0032] The bipolar transistor 310 (second bipolar transistor) is a
transistor that imitates operation of the bipolar transistor 300.
The RF signal (RF.sub.IN) is input to the base of the bipolar
transistor 310 via the capacitor 320. The collector of the bipolar
transistor 310 is connected to the resistor 332. The emitter of the
bipolar transistor 310 is grounded. In addition, the bias current
is supplied to the base of the bipolar transistor 310 via the
resistor 330 (third resistor). An amplified signal obtained by
amplifying the RF signal (RF.sub.IN) is output from the collector
of the bipolar transistor 310. In other words, the collector
current of the bipolar transistor 310 is at a level that
corresponds to the RF signal (RF.sub.IN).
[0033] The emitter area of the bipolar transistor 310 may be
smaller than the emitter area of the bipolar transistor 300.
Consumption of current in the bias circuit 230A can be reduced by
making the emitter area of the bipolar transistor 310 smaller.
[0034] The control voltage V.sub.2 (second control voltage) is
supplied to a first terminal of the resistor 332 (first resistor)
and a second terminal of the resistor 332 is connected to the
collector of the bipolar transistor 310. The collector current of
the bipolar transistor 310 flows to the resistor 332. Thus, a
control voltage V.sub.3 (third control voltage) that corresponds to
the collector current of the bipolar transistor 310 is generated at
the second terminal of the resistor 332.
[0035] The bipolar transistor 311 (third bipolar transistor) is a
transistor for generating a bias current (first bias current) to be
supplied to the bipolar transistors 300 and 310. A power supply
voltage (for example, battery voltage V.sub.BAT) is supplied to the
collector of the bipolar transistor 311. The base of the bipolar
transistor 311 is connected to the base of the bipolar transistor
313. A control voltage V.sub.4 (first control voltage), which is
for controlling the bias current, is supplied to the base of the
bipolar transistor 311. The emitter of the bipolar transistor 311
is connected to the resistors 302 and 330. A bias current (first
bias current) that corresponds to the control voltage V.sub.4 is
output from the emitter of the bipolar transistor 311.
[0036] The bipolar transistor 312 (fourth bipolar transistor) is a
transistor for generating a bias current (second bias current) to
be supplied to the bipolar transistors 300 and 310. A power supply
voltage (for example, battery voltage V.sub.BAT) is supplied to the
collector of the bipolar transistor 312. The base of the bipolar
transistor 312 is connected to a first terminal of the resistor
333. A second terminal of the resistor 333 is connected to the
second terminal of the resistor 332. Therefore, the control voltage
V.sub.3 (third control voltage) (actually, a voltage that is lower
than the control voltage V.sub.3 by an amount corresponding to the
base current of bipolar transistor 312) is supplied to the base of
the bipolar transistor 312 via the resistor 333. The emitter of the
bipolar transistor 312 is connected to the resistors 302 and 330. A
bias current (second bias current) that corresponds to the control
voltage V.sub.3 is output from the emitter of the bipolar
transistor 312.
[0037] The control voltage V.sub.1 (fourth control voltage) is
supplied to a first terminal of the resistor 331 (fifth resistor)
and a second terminal of the resistor 331 is connected to the
collector of the bipolar transistor 313.
[0038] The base and the collector of the bipolar transistor 313
(fifth bipolar transistor) are connected to each other, the base of
the bipolar transistor 313 is connected to the base of the bipolar
transistor 311, and the emitter of the bipolar transistor 313 is
connected to the collector of the bipolar transistor 314 (sixth
bipolar transistor). The base and the collector of the bipolar
transistor 314 are connected to each other and the emitter of the
bipolar transistor 314 is grounded. The control voltage V.sub.4
corresponding to the control voltage V.sub.1 is output from the
base of the bipolar transistor 313.
[0039] A first terminal of the capacitor 321 is connected to the
base of the bipolar transistor 313 and a second terminal of the
capacitor 321 is grounded.
[0040] The bipolar transistors 300, 310 and 314 are thermally
coupled with each other in the amplification circuit 200A and the
bias circuit 230A. In other words, the bipolar transistors 300, 310
and 314 are arranged close to each other on an integrated circuit
such that when the temperature of one transistor varies, the
temperatures of the other transistors also vary.
[0041] Operation of the amplification circuit 200A and the bias
circuit 230A will be described next.
[0042] The gain of the amplification circuit 200A changes when the
temperature of the bipolar transistor 300 changes due to the
operation of the bipolar transistor 300. Specifically, when the
temperature changes, the common-emitter current amplification
factor (hereafter, simply "current amplification factor") .beta.
and the base-emitter voltage V.sub.BE change. The current
amplification factor .beta. and the base-emitter voltage V.sub.BE
both decrease as the temperature increases. Assuming that the base
voltage and the collector voltage of the bipolar transistor 300 are
constant, a decrease in the current amplification factor .beta.
causes an idling current to decrease. In addition, a decrease in
the base-emitter voltage V.sub.BE causes the idling current to
increase. Here, the current amplification factor .beta. and the
base-emitter voltage V.sub.BE contribute different amounts to the
idling current and therefore the gain of the amplification circuit
200A varies with changes in the current amplification factor .beta.
and the base-emitter voltage V.sub.BE.
[0043] For example, if it is assumed that the bias current
I.sub.BIAS is constant, the gain of the amplification circuit 200A
decreases when the current amplification factor .beta. of the
bipolar transistor 300 decreases due to an increase in temperature.
At this time, since the bipolar transistor 310 imitates the
operation of the bipolar transistor 300, the bipolar transistor 310
undergoes a similar change in temperature to the bipolar transistor
300. Therefore, the current amplification factor .beta. of the
bipolar transistor 310 decreases and the control voltage V.sub.3
increases. When the control voltage V.sub.3 increases, the bias
current output from the emitter of the bipolar transistor 312
increases. Thus, the bias current I.sub.BIAS supplied to the
bipolar transistor 300 increases and a decrease in the gain of the
amplification circuit 200A is suppressed.
[0044] Since the bipolar transistors 300 and 310 are thermally
coupled with each other in the amplification circuit 200A and the
bias circuit 230A, changes in the current amplification factor
.beta. that occur with changes in temperature can be more
accurately connected to each other.
[0045] Furthermore, for example, if it assumed that the bias
current is constant, the gain of the amplification circuit 200A
increases when the base-emitter voltage V.sub.BE of the bipolar
transistor 300 decreases due to an increase in temperature. The
bipolar transistors 300 and 314 are thermally coupled with each
other in the amplification circuit 200A and the bias circuit 230A.
Therefore, the bipolar transistor 314 undergoes a similar change in
temperature to the bipolar transistor 300. Therefore, the
base-emitter voltage V.sub.BE of the bipolar transistor 314
decreases and the control voltage V.sub.4 decreases. When the
control voltage V.sub.4 decreases, the bias current output from the
emitter of the bipolar transistor 311 decreases. Thus, the bias
current I.sub.BIAS supplied to the bipolar transistor 300 decreases
and an increase in the gain of the amplification circuit 200A is
suppressed.
[0046] Thus, variations in gain caused by changes in the
temperature of the bipolar transistor 300 can be suppressed in the
amplification circuit 200A and the bias circuit 230A. In addition,
by configuring the bias circuit 230A to control the bias current,
an increase in circuit scale is reduced compared with the case
where a differential amplifier is used.
[0047] Furthermore, in the amplification circuit 200A, the RF
signal (RF.sub.IN) is supplied to a point between the resistor 302
and the base of the bipolar transistor 300 via the capacitor 301.
Similarly, in the bias circuit 230A, the RF signal (RF.sub.IN) is
supplied to a point between the resistor 330 and the base of the
bipolar transistor 310 via the capacitor 320. Thus, the path along
which the RF signal (RF.sub.IN) is supplied to the bipolar
transistor 310 is the same as the path along which the RF signal
(RF.sub.IN) is supplied to the bipolar transistor 300. For example,
if there were a resistor on the path along which the RF signal
(RF.sub.IN) is supplied to the bipolar transistor 310, an
alternating-current component of the RF signal (RF.sub.IN) would be
attenuated and the accuracy with which the bipolar transistor 310
imitates the bipolar transistor 300 would decrease. In the
configuration illustrated in FIG. 3, the RF signal (RF.sub.IN) is
supplied along the same path to the bipolar transistors 300 and 310
and therefore a decrease in the imitation accuracy of the bipolar
transistor 310 can be prevented. Thus, the effect of suppressing
variations in gain that occur with changes in temperature is
improved.
[0048] The suppression of variations in gain that occur with
changes in the current amplification factor .beta. in the
amplification circuit 200A and the bias circuit 230A of this
embodiment will be described by using simulation results. FIG. 4
illustrates the configuration of a comparative example, which is
for comparison with this embodiment. The comparative example
includes the amplification circuit 200A and a bias circuit 400.
Elements that are the same as those illustrated in FIG. 3 are
denoted by the same symbols and description thereof is omitted.
[0049] As illustrated in FIG. 4, the bias circuit 400 includes the
bipolar transistors 311, 313 and 314, a capacitor 321 and a
resistor 331. The bias circuit 400 does not include the bipolar
transistors 310 and 312, the capacitor 320 and the resistors 330,
332 and 333 of the bias circuit 230A. In other words, the bias
circuit 400 does not include a part that suppresses gain variations
of the amplification circuit 200A caused by changes in the current
amplification factor .beta. that occur with changes in the
temperature of the bipolar transistor 300. In addition, the bipolar
transistors 300 and 314 are thermally coupled with each other.
[0050] FIG. 5 illustrates simulation results for the comparative
example illustrated in FIG. 4. In FIG. 5, the horizontal axis
represents time (seconds) and the vertical axis represents output
power (dBm). The vertical axis is normalized such that a target
level of the output power is zero. A target level, an upper limit
and a lower limit of the output power are illustrated in FIG. 5.
FIG. 5 illustrates results obtained by outputting a pulse signal
such that the output power comes to be at the target level. In the
results illustrated in FIG. 5, in particular, the gain varies in a
period of around 200 microseconds after the start of operation.
[0051] FIG. 6 illustrates simulation results for the amplification
circuit 200A and the bias circuit 230A of this embodiment. The
horizontal axis and the vertical axis represent the same variables
as in FIG. 5. FIG. 6 illustrates results obtained by outputting a
pulse signal such that the output power comes to be at the target
level, similarly to as in FIG. 5. In the results illustrated in
FIG. 6, in particular, it is clear that the size of the variation
in gain is reduced in the period of around 200 microseconds after
the start of operation when compared with the results illustrated
in FIG. 5. Thus, it is also clear from these simulation results
that the variations in gain that occur with changes in the current
amplification factor .beta. are suppressed in the amplification
circuit 200A and the bias circuit 230A of this embodiment.
[0052] FIG. 7 illustrates the configurations of an amplification
circuit 200B and a bias circuit 230B, which are example
configurations of the amplification circuit 200 and the bias
circuit 230. Elements that are the same as those of the
amplification circuit 200A and the bias circuit 230A illustrated in
FIG. 3 are denoted by the same symbols and description thereof is
omitted.
[0053] The amplification circuit 200B does not include the
capacitor 301 and the resistor 302 of the amplification circuit
200A illustrated in FIG. 3. The bias circuit 230B does not include
the capacitor 320 of the bias circuit 230A illustrated in FIG. 3.
The RF signal (RF.sub.IN) is input to the bases of the bipolar
transistors 300 and 310 via a capacitor 700. In addition, a first
terminal of the resistor 330 (fourth resistor) is connected to the
emitters of the bipolar transistors 311 and 312 and a second
terminal of the resistor 330 is connected to the bases of the
bipolar transistors 300 and 310. In other words, in the
configuration illustrated in FIG. 7, the capacitor 700 and the
resistor 330 are shared by the amplification circuit 200B and the
bias circuit 230B. With this configuration as well, the same effect
as with the configuration illustrated in FIG. 3 can be attained.
Furthermore, the circuit scale of the power amplification module
112 can be reduced as result of the capacitor 700 and the resistor
330 being shared.
[0054] FIG. 8 illustrates the configurations of the amplification
circuit 200A and a bias circuit 230C, which are example
configurations of the amplification circuit 200 and the bias
circuit 230. Elements that are the same as those of the
amplification circuit 200A and the bias circuit 230A illustrated in
FIG. 3 are denoted by the same symbols and description thereof is
omitted.
[0055] The bias circuit 230C includes a bipolar transistor 800 and
a resistor 810 in addition to the elements included in the bias
circuit 230A illustrated in FIG. 3. The bipolar transistor 800 is
an HBT, for example. The collector of the bipolar transistor 800
(seventh bipolar transistor) is connected to the emitters of the
bipolar transistors 311 and 312, the base of the bipolar transistor
800 is connected to the base of the bipolar transistor 314 via the
resistor 810 (sixth resistor) and the emitter of the bipolar
transistor 800 is grounded. The bipolar transistor 800 is thermally
coupled with the bipolar transistor 300.
[0056] With the configuration illustrated in FIG. 8, degradation of
the linearity of the power amplification module 112 can be
suppressed by providing the bipolar transistor 800 in the bias
circuit 230C. This will be explained below.
[0057] In the bias circuit 230C, a bias current is output from the
emitters of the bipolar transistors 311 and 312. Here, the bias
current exhibits amplitude variations due to the effect of the RF
signal (RF.sub.IN). When the level of the RF signal (RF.sub.IN)
becomes large, the amplitude of the bias current also becomes
large. When the amplitude of the bias current becomes large, a
negative current (current in direction from resistors 302 and 330
toward emitters of bipolar transistors 311 and 312) is
generated.
[0058] The negative current might be cut by the rectification
action of the base-emitter PN junctions of the bipolar transistors
311 and 312 in the case of a configuration that does not include
the bipolar transistor 800 (in other words, bias circuit 230A
illustrated in FIG. 3). When the negative current is cut, the
average bias current increases and the gain of the amplification
circuit 200A becomes larger. The increase in the gain of the
amplification circuit 200A leads to a decrease in the linearity of
the power amplification module 112.
[0059] In the bias circuit 230C, the negative current flows to
ground via the bipolar transistor 800. Therefore, since the
negative part of the bias current is not cut in the bias circuit
230C, an increase in the average bias current in the case where the
level of the RF signal (RF.sub.IN) becomes large can be suppressed.
Thus, degradation of the linearity of the gain in the power
amplification module 112 can be suppressed.
[0060] Thus, in addition to achieving the same effect as with the
configuration illustrated in FIG. 3, degradation of the linearity
of the gain in the power amplification module 112 can be suppressed
with the configuration illustrated in FIG. 8.
[0061] Furthermore, the resistor 810 is provided between the base
of the bipolar transistor 314 and the base of the bipolar
transistor 800 in the configuration illustrated in FIG. 8. As a
result, the size of the current that flows to the bipolar
transistor 800 can be adjusted.
[0062] In addition, the bipolar transistor 800 is thermally coupled
with the bipolar transistor 300 in the configuration illustrated in
FIG. 8. As a result, the size of the current that flows to the
bipolar transistor 800 is adjusted with changes in the temperature
of the bipolar transistor 800.
[0063] A configuration similar to that illustrated in FIG. 8 can be
adopted for the configuration illustrated in FIG. 7 as well.
[0064] FIG. 9 illustrates configurations of the amplification
circuit 200A and a bias circuit 230D, which are example
configurations of the amplification circuit 200 and the bias
circuit 230. Elements that are the same as those of the
amplification circuit 200A and the bias circuit 230A illustrated in
FIG. 3 are denoted by the same symbols and description thereof is
omitted.
[0065] The bias circuit 230D includes field effect transistors
(FETs) 900, 901 and 902 instead of the bipolar transistors 311, 312
and 313 of the bias circuit 230A.
[0066] The battery voltage V.sub.BAT is supplied to the drain of
the FET 900 (first field effect transistor). The gate of the FET
900 is connected to the gate of the FET 902. The control voltage
V.sub.4 is supplied to the gate of the FET 900. The source of the
FET 900 is connected to the resistors 302 and 330.
[0067] The battery voltage V.sub.BAT is supplied to the drain of
the FET 901 (second field effect transistor). The gate of the FET
901 is connected to the first terminal of the resistor 333. The
second terminal of the resistor 333 is connected to the second
terminal of the resistor 332. Therefore, the control voltage
V.sub.3 (actually, a voltage that is lower than the control voltage
V.sub.3 by an amount corresponding to the gate current of the FET
901) is supplied to the gate of the FET 901 via the resistor 333.
The source of the FET 901 is connected to the resistors 302 and
330.
[0068] The drain of the FET 902 (third field effect transistor) is
connected to the second terminal of the resistor 331. The gate and
the drain of the FET 902 are connected to each other, the gate of
the FET 902 is connected to the gate of the FET 900 and the source
of the FET 902 is connected to the collector of the bipolar
transistor 314. The control voltage V.sub.4 corresponding to the
control voltage V.sub.1 is output from the gate of the FET 902.
[0069] In the bias circuit 230D, the FETs 900, 901 and 902 operate
in the same ways as the bipolar transistors 311, 312 and 313 of the
bias circuit 230A. Thus, the same effect can be achieved with the
bias circuit 230D as with the bias circuit 230A. In addition, in
the bias circuit 230D, as a result of using the FETs 900, 901 and
902, lower voltage operation is possible compared with the case
where the bipolar transistors 311, 312 and 313 are used.
[0070] The FETs 900, 901 and 902 may be provided instead of the
bipolar transistors 311, 312 and 313 in the bias circuit 230B
illustrated in FIG. 7 and the bias circuit 230C illustrated in FIG.
8 as well.
[0071] Exemplary embodiments of the present disclosure have been
described above. In the configuration illustrated in FIG. 3, the
bias current output from the bipolar transistor 312 is controlled
in accordance with the collector current of the bipolar transistor
310 that imitates the operation of the bipolar transistor 300.
Thus, variations in gain caused by changes in the temperature of
the bipolar transistor 300 can be suppressed. Furthermore, since a
differential amplifier is not needed as a part for controlling the
bias current in the bias circuit 230A, an increase in circuit scale
can be suppressed. The same is true for the configurations
illustrated in FIGS. 7 to 9 as well.
[0072] In addition, in the configuration illustrated in FIG. 3,
since the bipolar transistors 300 and 310 are thermally coupled
with each other, the accuracy with which the bipolar transistor 310
imitates the operation of the bipolar transistor 300 is improved
and the effect of suppressing variations in gain caused by changes
in the temperature of the bipolar transistor 300 is improved. The
same is true for the configurations illustrated in FIGS. 7 to 9 as
well.
[0073] Furthermore, in the configuration illustrated in FIG. 3, the
emitter area of the bipolar transistor 310 that imitates the
operation of the bipolar transistor 300 is smaller than the emitter
area of the bipolar transistor 300. Therefore, the current
consumption can be reduced. The same is true for the configurations
illustrated in FIGS. 7 to 9 as well.
[0074] In addition, in the configuration illustrated in FIG. 3, the
path along which the RF signal (RF.sub.IN) is supplied to the
bipolar transistor 310 is the same as the path along which the RF
signal (RF.sub.IN) is supplied to the bipolar transistor 300. Thus,
a reduction in the imitation accuracy of the bipolar transistor 310
is prevented and the effect of suppressing variations in gain
caused by changes in temperature is improved. The same is true for
the configurations illustrated in FIGS. 7 to 9 as well.
[0075] In addition, the bipolar transistor 314 is thermally coupled
with the bipolar transistor 300 in the configuration illustrated in
FIG. 3. Therefore, the base-emitter voltage V.sub.BE of the bipolar
transistor 314 changes with the base-emitter voltage V.sub.BE of
the bipolar transistor 300. The control voltage V.sub.4 supplied to
the base of the bipolar transistor 311 changes in conjunction with
changes in the base-emitter voltage V.sub.BE of the bipolar
transistor 314, and consequently the bias current output from the
bipolar transistor 311 changes. Thus, variations in gain caused by
changes in the temperature of the bipolar transistor 300 can be
suppressed. The same is true for the configurations illustrated in
FIGS. 7 to 9 as well.
[0076] Furthermore, in the configuration illustrated in FIG. 8, a
negative current generated when the level of the RF signal
(RF.sub.IN) becomes large (current in direction from resistors 302
and 330 toward emitters of bipolar transistor 311 and 312) flows to
ground via the bipolar transistor 800. Therefore, an increase in
the average bias current is suppressed and degradation of the
linearity of the gain in the power amplification module 112 can be
suppressed.
[0077] In addition, the resistor 810 is provided between the base
of the bipolar transistor 314 and the base of the bipolar
transistor 800 in the configuration illustrated in FIG. 8. As a
result, the size of the current that flows to the bipolar
transistor 800 can be adjusted.
[0078] Furthermore, the bipolar transistor 800 is thermally coupled
with the bipolar transistor 300 in the configuration illustrated in
FIG. 8. As a result, the size of the current that flows to the
bipolar transistor 800 is adjusted with changes in the temperature
of the bipolar transistor 800.
[0079] In addition, in the configuration illustrated in FIG. 9, the
FETs 900, 901 and 902 are provided instead of the bipolar
transistors 311, 312 and 313 in the configuration illustrated in
FIG. 3. Thus, lower voltage operation is possible compared with the
case where the bipolar transistors 311, 312 and 313 are used.
[0080] The purpose of the embodiments described above is to enable
easy understanding of the present disclosure and the embodiments
are not to be interpreted as limiting the present disclosure. The
present disclosure can be modified or improved without departing
from the gist of the disclosure and equivalents to the present
disclosure are also included in the present disclosure. In other
words, appropriate design changes made to the embodiments by one
skilled in the art are included in the scope of the present
disclosure so long as the changes have the characteristics of the
present disclosure. For example, the elements included in the
embodiments and the arrangements, materials, conditions, shapes,
sizes and so forth of the elements are not limited to those
exemplified in the embodiments and can be appropriately changed. In
addition, the elements included in the embodiments can be combined
as much as technically possible and such combined elements are also
included in the scope of the present disclosure so long as the
combined elements have the characteristics of the present
disclosure.
[0081] While embodiments of the disclosure have been described
above, it is to be understood that variations and modifications
will be apparent to those skilled in the art without departing from
the scope and spirit of the disclosure. The scope of the
disclosure, therefore, is to be determined solely by the following
claims.
* * * * *