Amplifiers – With semiconductor amplifying device – Including current mirror amplifier
Reexamination Certificate
2002-06-12
2004-06-15
Mottola, Steven J. (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including current mirror amplifier
C330S296000
Reexamination Certificate
active
06750720
ABSTRACT:
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/JP00/07085 which has an International filing date of Oct. 12, 2000, which designated the United States of America.
TECHNICAL FIELD
The present invention relates to a high frequency amplifying device for use in a satellite communication, ground microwave communication, mobile communication, and the like.
BACKGROUND ART
Generally, a high frequency amplifier using an NPN bipolar transistor of the BJT, HBT, or the like takes on a constant voltage biasing circuit that applies a constant voltage to the base in order to achieve a high power output and high efficiency. When a constant bias current is applied to the base, and when power of a high frequency input signal increases and generates a rectified current, the base voltage drops in order to maintain the constant current. Accordingly, when the power of input signal increases, since the amplifier operation rapidly approaches to the B-class, the saturation power decreases, and the high power output and high efficiency cannot be achieved. When a constant bias voltage is applied to the base, on the other hand, since the base voltage will not drop, the biasing class does not change, and a greater saturation power output and higher efficiency can be attained in comparison to the case of the constant current biasing. Therefore, a constant voltage biasing circuit that does not lower the base voltage, becomes necessary even when there is an increase of the base current with an increase of the power of input signal.
FIG. 1
is a circuit diagram illustrating a high frequency amplifying device, in that a base current compensating current mirror circuit is used for the constant voltage biasing circuit, which is presented, for example, in “Introduction To Functional Circuit Design of Analog ICs, IC Designing Method Using Circuit Simulator SPICE” (written by Hidehiko Aoki, issued by the CQ publisher, Sep. 20, 1992, page 74).
In the drawing, reference numeral
1
signifies a high frequency amplifier using an NPN bipolar transistor such as the BJT, HBT, or the like, as the amplifying element, and
2
signifies a constant voltage biasing circuit that supplies a base bias voltage to the high frequency amplifier
1
.
In the high frequency amplifier
1
, reference numeral
3
signifies an NPN bipolar transistor such as the BJT, HBT, or the like,
4
signifies the ground connected to the emitter terminal of the NPN bipolar transistor
3
,
5
signifies a high frequency signal in,put terminal,
6
signifies a high frequency signal output terminal,
7
signifies a base bias terminal,
8
signifies a collector bias terminal.
In the constant voltage biasing circuit
2
, reference numeral
11
signifies an NPN bipolar transistor such as the BJT, HBT, or the like, which configures a current mirror circuit together with the NPN bipolar transistor
3
of the high frequency amplifier
1
, whose base terminal is connected to the base bias terminal
7
, whose emitter terminal is connected to the ground
4
. Reference numeral
12
signifies an NPN bipolar transistor such as the BJT, HBT, or the like, for a base current compensation, whose base terminal is connected to the collector terminal of the NPN bipolar transistor
11
, whose emitter terminal is connected to the base terminal of the NPN bipolar transistor
11
. Reference numeral
13
signifies a resistor connected between the collector terminal of the NPN bipolar transistor
12
and a power supply/voltage setting terminal
15
, and
14
signifies a resistor connected between the base terminal of the NPN bipolar transistor
12
and the power supply/voltage setting terminal
15
.
Next, the operation will be described.
A high frequency signal Pin is input to the high frequency amplifier
1
through the high frequency signal input terminal
5
, and is output from the high frequency signal output terminal
6
, after being amplified by the high frequency amplifier
1
. A base voltage Vb and a base current Ibrf to the high frequency amplifier
1
are supplied from the constant voltage biasing circuit
2
, and a collector current Icrf and a collector voltage Vc to the high frequency amplifier
1
are supplied from the collector bias terminal
8
.
In the constant voltage biasing circuit
2
, the base voltage Vb and the base current Ibrf are determined as follows. Here, it is supposed that a size of the NPN bipolar transistor
11
that forms the current mirror together with the high frequency amplifier,
1
is 1, a size of the NPN bipolar transistor
3
of the high frequency amplifier
1
is N, and a size of the NPN bipolar transistor
12
for the base current compensation is M. Also, it is supposed that these three NPN bipolar transistors
3
,
11
,
12
have the same structure and the same current amplification factor &bgr;. Further, the contact voltage Vref, the currents Iref, Icdc
1
, Ibdc
1
, Icdc
2
, Iedc
2
, Ibdc
2
, Ibrf, Icrf, and the resistor Rref are defined as shown in FIG.
1
.
When a power supply voltage Vpc is supplied from the power supply/voltage setting terminal
15
of the constant voltage biasing circuit
2
, the reference current Iref of the current mirror is given by the following expression.
Iref=(Vpc−2*Vb)/Rref
With regard to this reference current Iref, the collector current Icrf of the NPN bipolar transistor
3
of the high frequency amplifier
1
is given as follows.
Icrf
=
N
1
+
1
+
N
β
·
(
1
+
β
)
Iref
Where the base bias voltage Vb of the NPN bipolar transistor
3
of the high frequency amplifier
1
is set as follows.
Vb=(Vpc−Iref*Rref)/2
The base current Ibrf flowing in this case becomes as follows.
Ibrf=Icrf/&bgr;
In this manner, the constant voltage biasing circuit
2
supplies the base voltage Vb and the base current Ib as the output thereof.
Since the conventional high frequency amplifying device is configured as above, when the high frequency input signal Pin increases and generates a base rectified current &Dgr;Ib, the base voltage Vb lowers by a voltage drop of &Dgr;Vb. Therefore, when the high frequency input signal Pin increases, the biasing class of the high frequency amplifier
1
approaches to the B-class, and the saturation output power and efficiency are decreased, which is a problem. Hereunder, the operation to cause the voltage drop &Dgr;Vb will be explained.
In the conventional technique, a case will be examined, in which the input power of the high frequency amplifier
1
increases and generates the base rectified current of &Dgr;Ib, and consequently the constant voltage biasing circuit
2
increases the output of the base current Ibrf by &Dgr;Ib. When the base current Ibrf increases by &Dgr;Ib, assuming that the emitter current Iedc
2
of the NPN bipolar transistor
12
for the base current compensation increases by &Dgr;Iedc
2
, and the base current Ibdc
1
of the NPN bipolar transistor
11
that forms the current mirror decreases by &Dgr;Ibdc
1
, there is the following relation on the variations of these currents.
&Dgr;Ib=&Dgr;Iedc
2
+&Dgr;Ibdc
1
Next, a variation &Dgr;Icdc
1
of the base current Icdc
1
of the NPN bipolar transistor
11
that forms the current mirror is given as follows.
&Dgr;Icdc
1
=−&bgr;*&Dgr;Ibdc
1
Here, assuming that the reference current Iref is almost constant, a variation &Dgr;Ibdc
2
of the base current Ibdc
2
of the NPN bipolar transistor
12
for the base current compensation is given as follows.
&Dgr;Ibdc
2
=−&Dgr;Icdc
1
=&bgr;*&Dgr;Ibdc
1
Therefore, the variation &Dgr;Iedc
2
of the emitter current Iedc
2
of the NPN bipolar transistor
12
for the base current compensation is given as follows.
&Dgr;Iedc
2
=(1+&bgr;)*&Dgr;Ibdc
2
=&bgr;*(1+&bgr;)*&Dgr;Ibdc
1
Therefore,
&Dgr;Ib=&Dgr;Iedc
2
+&Dgr;Ibdc
1
=&Dgr;Ibdc
1
*{1+&bgr;*(1+&bgr;)}=&Dgr;Ibdc
1
*(1+&bgr;+&bgr;
2
)
Therefore, &Dgr;Ibdc
1
is given as follows.
Δ
Ibdc1
=
Δ
&
Ikeda Yukio
Joba Hiroyuki
Mori Kazutomi
Shinjo Shintarou
Takagi Tadashi
Mitsubishi Denki & Kabushiki Kaisha
Mottola Steven J.
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