Amplifiers – With semiconductor amplifying device – Including frequency-responsive means in the signal...
Reexamination Certificate
2002-09-12
2004-05-04
Choe, Henry (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including frequency-responsive means in the signal...
C330S300000, C330S307000, C333S032000
Reexamination Certificate
active
06731174
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to radio frequency power amplifiers and in particular to a radio frequency power amplifier device for use in a radio frequency power amplifier.
BACKGROUND OF THE INVENTION
Radio frequency (RF) power amplifier devices for use in wireless transmission applications, such as RF power amplifiers, are typically implemented in an integrated circuit. The integrated circuit includes an RF amplification element, typically an RF transistor such as a Laterally Diffused Metal Oxide Semiconductor (LDMOS), that amplifies an RF signal applied to the device. When an RF power amplifier device is utilized in an RF power amplifier, the RF power amplifier typically further includes an input matching circuit coupled to an input of the RF power amplifier device and an output matching circuit coupled to an output of the RF power amplifier device. The input and output matching circuits are designed to optimize the performance of the RF amplification element included in the RF power amplifier device.
RF transistors such as LDMOS have very low output impedances, making it difficult to design an output matching circuit that will optimize performance of the transistor. In order to facilitate use of such a transistor in an RF power amplifier, RF power amplifier device manufacturers typically incorporate an output matching circuit into the integrated circuit that includes the RF transistor. The output matching circuit is designed to move the output impedance of RF transistor to a different, higher, and more easily matched output impedance at the output of the RF power amplifier device.
Referring now to
FIGS. 1 and 2
, an exemplary RF power amplifier device of the prior art is illustrated.
FIG. 1
is a schematic diagram of RF power amplifier device
100
. Typically, RF power amplifier device
100
is implemented in an integrated circuit
200
, which integrated circuit is illustrated in FIG.
2
. RF power amplifier device
100
includes an RF transistor
106
, such as an LDMOS transistor or a Bipolar Junction Transistor (BJT), that amplifies an RF signal applied to the RF power amplifier device. Typically RF transistor
106
is an RF transistor die
206
that is embedded in the integrated circuit. RF power amplifier device
100
further includes an input
101
and an output
120
, an input matching circuit
102
coupled between input
101
and an input
105
of RF transistor
106
, and an output matching circuit
110
coupled between an output
107
of RF transistor
106
and output
120
. Input matching circuit
102
typically comprises an input inductive element
104
, such as multiple series input bond wires
202
. Each bond wire of the multiple bond wires
202
is coupled to a gate, in the case of an LDMOS transistor, or a base, in the case of a BJT, of RF transistor
106
.
Output matching circuit
110
comprises a shunt inductive element
112
and a series inductive element
118
that are each coupled to an output of RF transistor
106
. Shunt inductive element
112
typically comprises multiple shunt bond wires
212
that are each coupled to an output of RF transistor die
206
, typically a drain of an LDMOS transistor or a collector of a BJT. Series inductive element
118
typically comprises multiple series bond wires
218
that also are each coupled to the output of RF transistor die
206
. Ideally, shunt bond wires
212
and series bond wires
218
are coupled to RF transistor die
206
at the die plane in order to minimize any additional, undesired inductances that may result from moving them away from the die plane. Output matching circuit
110
further includes a shunt capacitor
114
, such as a metal oxide semiconductor capacitor (MOSCAP)
214
, coupled between shunt inductive element
112
, that is, shunt bond wires
212
, and ground
116
. Capacitive element
114
performs a direct current (DC) blocking function and further contributes to the output match provided by output matching circuit
110
.
As is well known in the art, an impedance of output circuit
110
, and in particular a value of each of elements
112
,
114
, and
118
, presented to RF transistor
106
by each of shunt bond wires
212
, capacitor
214
, and series bond wires
218
, varies with a frequency of the RF signal applied to RF amplifier device
100
. As a result, output matching circuit
110
provides an effective output match to RF transistor
106
only over a very limited bandwidth. Since any additional output matching circuitry must be coupled to output
120
of RF power amplifier device
100
, the shunt impedances
112
,
114
of output matching circuit
110
are isolated from external matching circuitry. In addition, since each bond wire of the multiple shunt bond wires
212
is limited in overall length by a package encasing RF power amplifier device
100
, the use of output matching circuit
110
, and RF, power amplifier device
100
, is limited to high frequency applications, such as frequencies of 2 gigahertz (GHz) and above. As a result, RF power devices that include internal matching circuitry are typically narrow band devices that are limited to high frequency applications.
Therefore, there is a need for an RF amplifier device that can be used across a wide band of frequencies and that can be designed into low frequency, as well as high frequency, applications.
REFERENCES:
patent: 4213141 (1980-07-01), Colussi
patent: 4617524 (1986-10-01), Beckenbach et al.
patent: 5257411 (1993-10-01), Minasi
patent: 5406224 (1995-04-01), Mikami et al.
patent: 6104259 (2000-08-01), Miyaura
Choe Henry
May Steven A.
Motorola Inc.
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