Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2000-08-11
2003-03-25
Nguyen, Patricia (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S255000, C330S276000, C330S264000
Reexamination Certificate
active
06538510
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to high-speed data communications. More specifically, the invention relates to an improved efficiency integrated current sink only line driver, which solves problems associated with the inherent transconductance difference between NMOS and PMOS devices.
BACKGROUND OF THE INVENTION
With the advancement of technology, and the need for instantaneous information, the ability to transfer digital information from one location to another, such as from a central office (CO) to a customer premise (CP), has become more and more important.
In a digital subscriber line (DSL) communication system, data is transmitted from a CO to a CP via a transmission line, such as a two-wire twisted pair, and is transmitted from the CP to the CO as well, either simultaneously or in different communication sessions. The same transmission line might be utilized for data transfers by both sites or the transmission to and from the CO might occur on two separate lines. In this regard reference is now directed to
FIG. 1
, which illustrates a prior art xDSL communication system
1
. Specifically,
FIG. 1
illustrates communication between a central office (CO)
10
and a customer premise (CP)
20
by way of twisted-pair telephone line
30
. While the CP
20
may be a single dwelling residence, a small business, or other entity, it is generally characterized as having plain old telephone system (POTS) equipment, such as a telephone
22
, a public switched telephone network (PSTN) modem
25
, a facsimile machine (not shown), etc. The CP
20
may also include an xDSL communication device, such as an xDSL modem
23
that may permit a computer
24
to communicate with one or more remote networks via the CO
10
. When a xDSL service is provided, a POTS filter
21
is interposed between the POTS equipment such as the telephone
22
and the twisted-pair telephone line
30
. As is known, the POTS filter
21
includes a low-pass filter having a cut-off frequency of approximately 4 kilohertz to 10 kilohertz, in order to filter high frequency transmissions from the xDSL modem
23
and to protect the POTS equipment.
At the CO
10
, additional circuitry is provided. Generally, a line card
18
(i.e., Line Card A) containing line interface circuitry is provided for electrically coupling a data transmission to the twisted-pair telephone line
30
. In fact, multiple line cards
14
,
18
may be provided (two shown for simplicity of installation) to serve a plurality of local loops. In the same way, additional circuit cards are typically provided at the CO
10
to handle different types of services. For example, an integrated services digital network (ISDN) interface card
16
, a digital loop carrier line card
19
, and other circuit cards supporting similar and other communication services, may be provided.
A digital switch
12
is also provided at the CO
10
and is configured to communicate with each of the various line cards
14
,
16
,
18
, and
19
. On the outgoing side of the CO (i.e., the side opposite the various local loops), a plurality of trunk cards
11
,
13
, and
15
are typically provided. For example, an analog trunk card
11
, a digital trunk card
13
, and an optical trunk card
15
are illustrated in FIG.
1
. Typically, these circuit cards have outgoing lines that support numerous multiplexed DSL service signal transmissions.
Having introduced a conventional xDSL communication system
1
as illustrated and described in relation to
FIG. 1
, reference is now directed to
FIG. 2
, which is a prior art functional block diagram illustrating the various elements in a xDSL communications link
40
between a line card
18
located within a CO
10
and a xDSL modem
23
located at a CP
20
. In this regard, the xDSL communications link
40
of
FIG. 2
illustrates transmission of data from a CO
10
to a CP
20
via a twisted-pair telephone transmission line
30
as may be provided by a POTS service provider to complete a designated xDSL communications link
40
between a CO
10
and a CP
20
. In addition,
FIG. 2
further illustrates the transmission of data from the CP
20
to the CO
10
via the same twisted-pair telephone transmission line
30
. With regard to the present illustration, data transmissions may be directed from the CP
20
to the CO
10
, from the CO
10
to the CP
20
or in both. directions simultaneously. Furthermore, data transmissions can flow on the same twisted-pair telephone transmission line
30
in both directions, or alternatively on separate transmission lines (one shown for simplicity of illustration). Each of the separate transmission lines may be designated to carry data transfers in a particular direction either to or from the CP
20
.
The CO
10
may include a line card
18
(see
FIG. 1
) that may comprise a CO-digital signal processor (DSP)
43
, a CO-analog front end (AFE)
45
, a CO-line driver
47
and a CO-hybrid
49
. As illustrated in
FIG. 2
, the CO-DSP
43
may receive digital information from one or more data sources (not shown) and may send the digital information to a CO-analog front end (AFE)
45
. The CO-AFE
45
interposed between the twisted-pair telephone transmission line
30
and the CO-DSP
43
may convert digital data, from the CO-DSP
43
, into a continuous time analog signal for transmission to the CP
20
via the one or more twisted-pair telephone transmission lines
30
.
One or more analog signal representations of digital data streams supplied by one or more data sources (not shown) may be converted in the CO-AFE
45
and further amplified and processed via a CO-line driver
47
before transmission by a CO-hybrid
49
, in accordance with the amount of power required to drive an amplified analog signal through the twisted-pair telephone transmission line
30
to the CP
20
.
As further illustrated in
FIG. 2
, a xDSL modem
23
located at a CP
20
may comprise a CP-DSP
42
, a CP-AFE
44
, a CP-line driver
46
, and a CP-hybrid
48
. The CP-hybrid
48
, located at the CP
20
, may de-couple a received signal from the transmitted signal in accordance with the data modulation scheme implemented by the particular xDSL data transmission standard in use. The CP-AFE
44
, located at the CP
20
, having received the de-coupled received signal from the CP-hybrid
48
, may then convert the received analog signal into a digital signal, which may then be transmitted to a CP-DSP
42
located at the CP
20
. Finally, the digital information may be further transmitted to one or more specified data sources such as the computer
24
(see FIG.
1
).
In the opposite data transmission direction, one or more digital data streams supplied by one or more devices in communication with the CP-DSP
42
at the CP
20
may be converted by the CP-AFE
44
and further amplified via CP-line driver
46
. The CP-hybrid
48
, located at the CP
20
, may then be used to couple the intended analog representations of the various digital signals to a transmit signal in accordance with the data modulation scheme implemented by the particular xDSL data transmission standard in use. As will be appreciated by those skilled in the art, the CP-line driver
46
may amplify and forward the transmit signal with the power required to drive an amplified analog signal through the twisted-pair telephone transmission line
30
to the CO
10
. It is significant to note that the CP-hybrid
48
is used to regenerate the transmit signal so the transmit signal may be subtracted from the receive signal when the DSL is receiving. As a result, the CP-hybrid
48
does not affect the transmitted signal in any way. The CO-AFE
45
may receive the data from the CO-hybrid
49
, located at the CO
10
, which may de-couple the signal received from the CP
20
from the signal transmitted by the CO
10
. The CO-AFE
45
may then convert the received analog signal into one or more digital signals, which may then be forwarded to the CO-DSP
43
located at the CO
10
. Finally, the digital information may be further distributed to one or more specified dat
Amrany Daniel
Ashley Frank
Larsen Frode
Muralt Arnold
Globespanvirata, Inc.
Nguyen Patricia
Thomas Kayden Horstemeyer & Risley
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