Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Lateral bipolar transistor structure
Reexamination Certificate
2002-03-21
2003-12-16
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Lateral bipolar transistor structure
C257S566000, C257S577000, C438S338000, C438S342000
Reexamination Certificate
active
06664609
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an integrated circuit device that includes a differential amplification circuit, and particularly to an improvement in the high-frequency operation of the integrated circuit device.
(2) Related Art
In recent years, active developments have been made in high-frequency integrated circuit devices for use in telecommunication equipment, aiming at further promoting broadband wireless communications. The high-frequency integrated circuit devices include circuits such as a Gilbert cell, in which a differential amplification circuit and an emitter follower are usually incorporated.
A “Gilbert cell” has a configuration in which a circuit formed by cross-connecting two differential amplification circuits is connected in series to one differential amplification circuit. It is also called a “Gilbert multiplier” (Paul R. Gray, Robert G. Meyer, “
Analysis and Design of Analog Integrated Circuits
”, John Wiley & Sons, 1977).
FIG. 1
is a circuit diagram showing a circuit configuration of a typical Gilbert cell. In
FIG. 1
, the Gilbert cell
1
includes input terminals T
14
and T
15
into which a high-frequency reception signal (an RF signal) is inputted, input terminals T
12
and T
13
into which a local-oscillator signal (an LO signal) is inputted, and output terminals T
10
and T
11
from which an intermediate frequency signal (an IF signal) that has a lower frequency is outputted.
The IF signal is generated by superimposing (a) a signal whose frequency equals to a sum of a frequency of the RF signal and a frequency of the LO signal and (b) a signal whose frequency equals to a difference between the frequency of the RF signal and the frequency of the LO signal. Note here that both the RF signal and the LO signal are balanced input, and therefore, the Gilbert cell
1
is a so-called double balanced mixer.
Transistors Tr
14
and Tr
15
and resistors R
10
and R
11
form a differential amplification circuit. The resistor R
10
is connected to an emitter of the transistor Tr
14
and the resistor R
11
is connected to an emitter of the transistor Tr
15
.
This differential amplification circuit is used as a linear amplification circuit. The resistors R
10
and R
11
are provided to increase an input voltage range of the differential amplification circuit. Specifically, an input dynamic range of the differential amplification circuit is adjusted by appropriately selecting resistance values of the resistors R
10
and R
11
.
Conventionally, it is common that circuit layouts of integrated circuit devices are determined based on circuit diagrams. A circuit layout of the above Gilbert cell is also determined based on a circuit diagram.
FIG. 2
shows an example of a conventional circuit layout of the Gilbert cell, particularly the transistors Tr
14
and Tr
15
, having the circuit configuration shown in FIG.
1
.
As
FIG. 2
shows, the transistors Tr
14
and Tr
15
are substantially symmetrical with respect to a dotted line L
2
. Also, the transistors Tr
14
and Tr
15
both have a multiple finger configuration, in which rectangular fingers of bases, emitters, and collectors are arranged alternately like the teeth of a comb. The fingers of the transistor Tr
14
and the fingers of the transistor Tr
15
are parallel to each other, and also, substantially parallel to the dotted line L
2
.
A collector wiring WC
20
of the transistor Tr
14
extends from collector fingers C
20
and C
21
. A base wiring WB
20
extends from base fingers B
20
, B
21
, and B
22
. An emitter wiring WE
20
extends from emitter fingers E
20
and E
21
.
The transistor Tr
15
also has the same configuration as the transistor Tr
14
. Specifically, a base wiring WB
21
, a collector wiring WC
21
, and an emitter wiring WE
21
respectively extend from base fingers B
23
to B
25
, collector fingers C
23
and C
24
, and emitter fingers E
23
and E
24
.
Here, a stray capacitance is generated between the two emitter wirings WE
20
and WE
21
. A condenser C
10
in
FIG. 1
is an equivalent circuit indicating this stray capacitance. To enable an electric current to flow thorough the resistors R
10
and R
11
, an electric charge corresponding to the stray capacitance needs to be accumulated. Therefore, an operation delay corresponding to the time taken for accumulating the electric charge is inevitable. This makes it difficult for an electric current to flow through the resistors R
10
and R
11
at the time of high-frequency operation. Accordingly, the adjustment of an input dynamic range of the differential amplification circuit formed by the transistors Tr
14
and Tr
15
becomes difficult. The problem is, therefore, that the Gilbert cell
1
may not be able to achieve desired performances at the time of high-frequency operation.
Here, although
FIG. 2
shows the transistors Tr
14
and Tr
15
each including seven fingers, the number of fingers may be increased to keep up with increased requirements of transistor performances. In this case, desired performances of the transistors may not be achieved at the time of high-frequency operation. As described above, integrated circuit devices that include a differential amplification circuit are known to suffer from various problems at the high-frequency operation. This has resulted in increasing demands for integrated circuit devices that can operate normally even in a high-frequency area.
SUMMARY OF THE INVENTION
In view of the above problems, the objective of the present invention is to provide an integrated circuit device that includes a differential amplification circuit and that can operate normally even at high frequency.
The above objective of the present invention can be achieved by an integrated circuit device, including: a first bipolar transistor; a second bipolar transistor that is positioned to be adjacent to the first bipolar transistor; a first wiring that is electrically connected to an emitter of the first bipolar transistor and extends therefrom into a direction opposite to the second bipolar transistor with respect to the first bipolar transistor; and a second wiring that is electrically connected to an emitter of the second bipolar transistor and extends therefrom into a direction opposite to the first bipolar transistor with respect to the second bipolar transistor, wherein the first bipolar transistor and the second bipolar transistor form a differential amplification circuit.
With this configuration, a stray capacity between the first emitter wiring and the second emitter wiring can be reduced, and therefore, the above-described case where an input dynamic range cannot be adjusted appropriately at the high-frequency operation can be avoided. This enables desired performances of the integrated circuit device to be achieved.
The above objective of the present invention can also be achieved by an integrated circuit device, including a Gilbert cell that includes the integrated circuit device, including: a first bipolar transistor; a second bipolar transistor that is positioned to be adjacent to the first bipolar transistor; a first wiring that is electrically connected to an emitter of the first bipolar transistor and extends therefrom into a direction opposite to the second bipolar transistor with respect to the first bipolar transistor; and a second wiring that is electrically connected to an emitter of the second bipolar transistor and extends therefrom into a direction opposite to the first bipolar transistor with respect to the second bipolar transistor, wherein the first bipolar transistor and the second bipolar transistor form a differential amplification circuit.
With this configuration, a Gilbert cell that can operate normally even at high frequency can be realized.
The above objective of the present invention can also be achieved by an integrated circuit device, including: a controlled-potential power source wiring; a first bipolar transistor; a second bipolar transistor that is positioned to be opposite to the first bipolar transistor with respect to the controlled-potential power s
Imanishi Ikuo
Ito Junji
Flynn Nathan J.
Matsushita Electric - Industrial Co., Ltd.
Wilson Scott R
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