Amplifiers – With semiconductor amplifying device – Including gain control means
Reexamination Certificate
2002-07-30
2004-08-31
Nguyen, Linh M. (Department: 2816)
Amplifiers
With semiconductor amplifying device
Including gain control means
C327S491000
Reexamination Certificate
active
06784743
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a high frequency amplifier which relaxes a drop in base potential of a bipolar transistor upon the input of a bulk power high frequency signal to thereby provide a high saturation characteristic.
The present invention also relates to a high frequency amplifier and a frequency mixer each of which relaxes a drop in base potential of a bipolar transistor upon input of a bulk power high frequency signal to thereby provide a high saturation characteristic and reduce degradation in a noise figure.
BACKGROUND ART
A conventional common emitter two stage type high frequency amplifier described in, for example, “IEEE Microwave Theory and Technology Symposium (1997) Preliminary Reports is one in that a DC bias produced from a current mirror circuit is supplied to a base terminal of a bipolar transistor as shown in FIG.
1
.
In the drawing, reference numeral
1
indicates an input terminal for a high frequency signal, reference numeral
2
indicates an output terminal for the high frequency signal, reference numerals
3
indicate amplifying bipolar transistors whose emitter terminals are grounded, reference numeral
4
indicates a constant voltage source, reference numerals
8
indicate bias feed inductors for supplying a DC bias from the constant voltage source
4
e
to collector terminals of the amplifying bipolar transistors
3
, reference numeral
9
indicates a bypass capacitor for short circuiting the high frequency signal, reference numeral
11
indicates a bias bipolar transistor, reference numeral
12
indicates a current mirror bias circuit, reference numerals
15
indicate bias feed resistors for supplying a DC bias from the current mirror bias circuit
12
to base terminals of the amplifying transistors
3
, reference numerals
16
indicate DC cut capacitors, reference numerals
19
indicate bias resistors, and reference numerals
28
indicate emitter loaded inductances.
The operation will next be described.
The conventional high frequency amplifier shown in
FIG. 1
amplifies the high frequency signal input from the input terminal
1
by the amplifying bipolar transistors
3
and takes out it from the output terminal
2
. In order to operate the amplifying bipolar transistors
3
, there is a need to supply DC biases to the collector and base terminals of the amplifying bipolar transistors
3
. The collector terminals thereof are supplied with the DC bias from the constant voltage source
4
e
via the bias feed inductors
8
, whereas the base terminals thereof are supplied with the DC bias from the current mirror bias circuit
12
via the bias feed resistors
15
.
In the above described conventional high frequency amplifier, a bias current supplied from the current mirror circuit increases with an increase in the base current of each amplifying bipolar transistor upon input of the bulk power high frequency signal. Therefore, the high frequency amplifier is accompanied by a problem that a voltage drop is developed across each bias feed resistor so that a base potential of each amplifying bipolar transistor is reduced, thereby degrading a saturation characteristic.
Further, a conventional common emitter high frequency amplifier described in, for example, Preliminary Reports of Communications Society Conference of the Institute of Electronics, Information and Communication Engineers (2001) is one in that a DC bias is supplied from a current mirror bias circuit and one diode switch to a base terminal of a bipolar transistor as shown in FIG.
2
.
In the drawing, reference numeral
101
indicates an input terminal for a high frequency signal, reference numeral
102
indicates an output terminal for the high frequency signal, reference numeral
103
indicates an amplifying bipolar transistor emitter terminal of which is grounded, reference numerals
104
a
and
104
b
indicate constant current sources, reference numeral
105
a
indicates a constant voltage source, reference numerals
106
a
and
106
b
indicate bias bipolar transistors, reference numeral
107
indicates a bias feed resistor for supplying the DC bias to the base terminal of the amplifying bipolar transistor
103
, reference numerals
108
a
and
108
b
indicate bias resistors, reference numeral
109
indicates a current mirror bias circuit which comprises the constant current source
104
a
, the constant voltage source
105
a
, the bias bipolar transistors
106
a
and
106
b
, the bias feed resistor
107
and the bias resistors
108
a
and
108
b
, reference numeral
112
a
indicates a switch bipolar transistor, reference numerals
113
a
and
113
b
indicate reference voltage bipolar transistors, and reference numeral
111
indicates a base bias compensating circuit which comprises the constant voltage source
104
b
, the switch bipolar transistor
112
a
and the reference voltage bipolar transistors
113
a
and
113
b.
The operation will now be described below.
The conventional high frequency amplifier shown in
FIG. 2
is one in that the high frequency signal input from the input terminal
101
is amplified by the amplifying bipolar transistor
103
, followed by extraction thereof from the output terminal
102
. When the high frequency signal power input to the input terminal
101
is sufficiently low, i.e., upon a linear operation of the amplifying bipolar transistor
103
, the DC bias to the base terminal of the amplifying bipolar transistor
103
is supplied mainly from the current mirror bias circuit
109
. When the high frequency signal power input to the input terminal
101
is high, i.e., upon a non linear operation of the amplifying bipolar transistor
103
, the DC bias is mainly supplied from the base bias compensating circuit
111
. Therefore, an improvement in saturation characteristic is performed by relaxing a drop in base potential VBE of the amplifying bipolar transistor
103
with an increase in the high frequency signal power.
The operation of the base bias compensating circuit
111
will now be described below.
The switch bipolar transistor
112
a
is a diode switch whose base terminal and collector terminals are short circuit connected. Such a switch is turned on/off by a difference in potential between the emitter terminal and the collector/base terminals. When the switch is turned on, a current flows between the collector and emitter thereof, whereas when it is turned off, no current ideally flows. Here, a voltage to be required for turning on the switch (Hereinafter refereed to as “on voltage of the switch”) is defined as VSW_ON.
Upon turning off of the diode switch, a current IREF
1
generated by the constant current source
104
b
flows into the two reference voltage generating bipolar transistors
113
a
and
113
b
whose base terminals and collector terminals are short circuit connected. Owing to the current IREF
1
, a voltage of VREF is produced at the base/collector terminal of the reference voltage bipolar transistor
113
a.
When the diode switch is turned off, i.e., a condition VSW_ON>VREF−VBE is established with respect to the base potential VBE of the amplifying bipolar transistor
103
, no current flows from the base bias compensating circuit
111
to the base terminal of the amplifying bipolar transistor
103
.
On the other hand, when the diode switch is turned on, i.e., a condition VSW_ON<VREF−VBE is established, a current flows between the collector and emitter of the switch bipolar transistor
112
a
and it is supplied to the base terminal of the amplifying bipolar transistor
103
as a DC bias.
As described above, the base bias compensating circuit
111
supplies the DC bias to the base terminal as it is driven by the base potential VBE of the amplifying bipolar transistor
103
, i.e., in response that the power of the high frequency signal input to the input terminal
101
increases.
In the above described conventional high frequency amplifier, though the drop in base potential is relaxed by virtue of an increase in the amount of supply of the current to the base terminal of the amplifying bipolar transistor
Ikushima Takayuki
Joba Hiroyuki
Maeda Ken-ichi
Sawaumi Chiemi
Suematsu Noriharu
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Linh M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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