Amplifiers – With semiconductor amplifying device – Including distributed parameter-type coupling
Reexamination Certificate
2002-11-20
2004-05-18
Nguyen, Patricia (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including distributed parameter-type coupling
C330S053000, C330S054000, C330S307000
Reexamination Certificate
active
06737921
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the construction of a distributed amplifier and differential distributed amplifier for use in high-frequency amplifiers in the microwave band, in the millimeter wave band, etc.
2. Description of the Related Art
Generally, when amplification is performed by using FETs, it is required to increase the total gate width of the FETs in order to obtain higher output. When the frequency to be used is high, even if the unit gate width is increased, this measure is ineffective because of electrical delay, gate resistance loss, etc., and accordingly a comb-shaped construction with a large number of gate fingers is adopted.
The construction of a known type of comb-shaped FET is shown in FIG.
9
. As shown in
FIG. 9
, the comb-shaped FET
80
is made of a unit FET
81
a
which is composed of a source electrode
84
, a drain electrodes
86
, and a gate electrode
85
disposed therebetween. A neighboring unit FET
81
b
has the same drain electrode
86
as the unit FET
81
a
. In this way, six unit FETs are constructed. These unit FETs are disposed so as to have a comb-shaped construction by using a source wiring
87
, a drain wiring
82
, and a gate wiring
88
. Moreover, the source wiring
87
is connected to grounding portions (source pads)
83
a
and
83
b
, the drain wiring
82
is connected to an output portion (drain pad)
90
, and the gate wiring
88
is connected to an input portion (gate pad)
89
. Here, the unit gate width of the unit FET is shown by
85
T.
The circuit diagram of a distributed amplifier using the comb-shaped FET of
FIG. 9
is shown in FIG.
10
. As shown in
FIG. 10
, in the distributed amplifier
100
, a plurality of unit FETs
112
each made of a source electrode
109
, a drain electrode
111
, and a gate electrode
110
are connected in parallel. An input portion
107
comprises an input terminal connected to the gate electrode of each unit FET through high-impedance transmission lines
105
. The opposite end of the input portion
107
is grounded through a terminating circuit made of a resistor
101
and a capacitor
103
. Furthermore, an output portion
108
comprises an output terminal connected to the drain electrode of each unit FET through high-impedance transmission lines
106
. The opposite end of the output portion
108
is grounded through a terminating circuit made of a resistor
102
and a capacitor
104
. Furthermore, the source electrode of each unit FET is grounded.
However, in the comb-shaped FET
80
, the lengths of the paths in which a signal passes inside the FET
80
are short in the unit FETs located close to the input portion
89
and the output portion
90
, that is, in the inside unit FETs, and the lengths of the paths are long in the outside unit FETs. Therefore, because of the difference in the paths in which a signal passes, when a signal is distributed to each gate electrode, a difference in phase of the signals is caused, and also there is a problem in that the phase difference is produced when the signals from all the drain electrodes are synthesized. Furthermore, when each source electrode is connected to the grounding portions
83
a
and
83
b
, since the line lengths, which are dependent on the location of each unit FET, are different from each other, there is a problem in that the source impedance is different from one unit FET to another.
In order to avoid such effects, as the frequency to be used increases, the size of the FETs is required to be reduced, but this is contradictory to the purpose of obtaining higher output. Therefore, there is a problem that it is difficult to increase the output even if a comb-shaped construction is adopted.
Moreover, in the distributed amplifier
100
using this comb-shaped FET, a resistor
101
is used in the terminal of the circuit which electrically connects the gate electrodes in consecutive order. Because of this, in low-noise amplifiers, there is a problem in that the NF (noise figure) increases. Furthermore, a resistor
102
is used in the terminal of the circuit which electrically connects the drain electrodes in consecutive order. Accordingly, in high-output amplifiers, there is a problem in that the electric power is consumed in the resistor
102
.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a distributed amplifier and differential distributed amplifier in which a low noise amplifier or high output amplifier can be easily fulfilled without causing phase differences.
According to a preferred embodiment of the present invention, a distributed amplifier may comprise two or more unit FETs, each having a source electrode, a drain electrode, and a belt-shaped gate electrode arranged therebetween, the unit FETs being substantially linearly arranged in the length direction of the gate electrode on a substrate; each pair of neighboring source electrodes, neighboring drain electrodes, and neighboring gate electrodes being electrically connected to each other by a respective circuit in consecutive order of the two or more unit FETs; and an input portion connected to one end of the circuit that connects the gate electrodes, and an output portion connected to one end of the circuit that connects the drain electrodes. In the distributed amplifier, an inductor or high-impedance transmission line may be provided in one or more of the connection portions in the circuits between the neighboring drain electrodes or between the neighboring gate electrodes; or a capacitor may be provided in one or more of the connection portions in the circuits between the drain electrodes and the source electrodes or between the gate electrodes and the source electrodes.
Furthermore, in a distributed amplifier of the present invention, a terminating circuit having any one of an inductor, a capacitor, and a transmission line or having a combination of these may be connected to the end opposite to the input portion of the circuit that connects the gate electrodes electrically in consecutive order.
Furthermore, in a distributed amplifier of the present invention, a terminating circuit having any one of an inductor, a capacitor, and a transmission line or having a combination of these may be connected to the end opposite to the output portion of the circuit that connects the drain electrodes electrically in consecutive order.
Furthermore, in a distributed amplifier of the present invention, a terminating circuit having any one of an inductor, a capacitor, and a transmission line or having a combination of these may be connected to the end opposite to the input portion of the circuit that connects the gate electrodes electrically in consecutive order and to the end opposite to the output portion of the circuit that connects the drain electrodes electrically in consecutive order.
Furthermore, in a distributed amplifier of the present invention, a terminating circuit having at least a resistor may be connected to the end opposite to the output portion of the circuit that connects the drain electrodes electrically connected in consecutive order.
Furthermore, in a distributed amplifier of the present invention, a terminating circuit having at least a resistor may be connected to the end opposite to the input portion of the circuit that connects the circuit gate electrodes electrically in consecutive order.
Furthermore, a differential distributed amplifier may comprise two of the distributed amplifiers described above; and a belt-shaped source wiring metal formed between the distributed amplifiers. In the differential distributed amplifier, the two distributed amplifiers are arranged symmetrically with respect to said source wiring metal with the respective source electrodes facing each other, and the source wiring metal interconnects the respective source electrodes of the pair of distributed amplifiers.
Furthermore, in the differential distributed amplifier, the terminating circuits connected to the ends opposite to the input portions of the respective
Murata Manufacturing Co. Ltd.
Nguyen Patricia
Ostrolenk Faber Gerb & Soffen, LLP
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