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参数资料
| 型号： | AD816 |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | 500 mA Differential Driver & Dual Low Noise (VF) Amplifiers(500mA差分驱动器和双低噪电压反馈放大器) |
| 中文描述： | 500毫安差分驱动器 |
| 文件页数： | 14/16页 |
| 文件大小： | 479K |
| 代理商： | AD816 |
AD816
REV. 0
–14–
APPLICATIONS
ADSL Transceiver
The AD816 is designed for the primary purpose of providing an
integrated solution for the transmit and receive functions of an
ADSL modem. ADSL or Asymmetrical Digital Subscriber Line
is a means for delivering up to 6 Mbps from a telephone central
office (CO) into a home over the conventional telephone twisted
pair (local loop) and a few hundred kbps simultaneously in the
opposite direction.
The transmit/receive block is commonly referred to as a hybrid,
which is an old telephone term, and the function was originally
performed with passive circuitry in early phone systems. The
hybrid’s function is to deliver maximum transmit power down
the line, while providing the receive circuitry with a maximum
receive signal and a minimized (self) transmit signal. As the line
gets longer, this separation becomes much more difficult,
because the transmit signal must be larger to reach the other
end with acceptable SNR, while the receive signal is more
attenuated by the longer line.
The figure of merit for the performance of the hybrid is
commonly called trans-hybrid loss and is a measure of how
much the transmit signal that appears in the receive circuit has
been attenuated relative to the amplitude of the transmit signal
itself. It is measured in dBs and is a function of frequency.
In addition to the passive circuits that have been used over time,
active circuit techniques can enhance the hybrid’s performance.
Figure 50 shows one of the various hybrid circuits that uses the
AD816 in an ADSL application. The high power op amps serve
as the transmitter, while the low noise amplifiers serve as the
receiver.
The power amplifiers of the AD816 (D1 and D2) are arranged
in a differential configuration that receives its inputs from the
differential outputs of a D/A converter. The outputs differen-
tially drive the transformer primary with a turns ratio of 1:2.
The line on the secondary side of the transformer has an imped-
ance of 120
. Thus one quarter of this resistance (30
) is
required for back termination on the primary side due to the
impedance scaling by the square of the turns ratio. This resis-
tance is divided in half (15
) and put on each side of the drive
buffers for symmetry (R101 and R201).
The receive section (R1 and R2) is configured as a pair of
difference amplifiers that together produce a differential output
that consists of the receive signal in addition to the transmit
signal attenuated by the trans-hybrid loss.
The circuit is highly symmetrical, so a single-ended explanation
can be easily generalized to understand the differential opera-
tion. D1 output terminals (Pin 6 of the AD816) drives the top
of the primary of T1 through R101. A voltage divider is formed
+15V
0.1 μF
10μF
8
6
715
4
5
–15V
7
9
715
11
10
D1
AD816
806
V+
V–
R202
196
R203
196
R204
1.18k
L201
12μH
R201
15
R101
15
2
3
1
R106
348
R105
162
R107
1k
R108
2.37k
RCV OUT+
1
2
4
10
9
6
8
7
5
T1
XFRMR
C601
0.1μF
C602
0.1μF
TELEPHONE
TWISTED PAIR
D2
0.1μF
10μF
R102
196
R103
196
R104
1.18k
C101
8.2μF
L101
12μH
R1
AD816
13
12
14
R206
348
R205
162
R207
1k
R208
2.37k
RCV OUT–
R2
AD816
C201
8.2μF
Figure 50. AD816 as an ADSL Transceiver
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| AD8170AR | 250 MHz, 10 ns Switching Multiplexers w/Amplifier |
| AD8170-EB | 250 MHz, 10 ns Switching Multiplexers w/Amplifier |
| AD8170AR-REEL | 250 MHz, 10 ns Switching Multiplexers w/Amplifier |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD816AVR | 制造商:Rochester Electronics LLC 功能描述:ADSL TRANSCEIVER - Bulk |
| AD816AY | 制造商:Rochester Electronics LLC 功能描述:ADSL TRANSCEIVER - Bulk |
| AD816AYR | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Analog IC |
| AD816AYS | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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