Datasheet

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SBOS317D − SEPTEMBER 2004 − REVISED AUGUST 2008
www.ti.com
17
Time (10ns/div)
Voltage (V)
3.0
2.5
2.0
1.5
1.0
0.5
0
+V
OUT
−
V
OUT
V
IN
=0Vto0.5V
R
G
=402
Ω
Figure 8. Pulse Response for Figure 7 Schematic
1/4
OPA4820
+5V
−
5V
1/4
OPA4820
294
Ω
77
Ω
50pF
100pF
294
Ω
77
Ω
100pF
250
Ω
250
Ω
V
O
V
I
1/4
OPA4820
1/4
OPA4820
121
Ω
161
Ω
50pF
500
Ω
100pF
G
D
=2,
ω
O
=2
π
10MHz, Q = 0.54G
D
=2,
ω
O
=2
π
10MHz, Q = 1.31
121
Ω
161
Ω
100pF
250
Ω
250
Ω
V
O
/V
I
=4V/V
f
−3dB
=10MHz
P
D
= 225mW
500
Ω
Figure 9. Low-Power, Differential I/O, 4th-Order Butterworth Active Filter
Frequency (MHz)
Differential Gain (dB)
110100
15
12
9
6
3
0
−
3
−
6
−
9
Figure 10. Differential 4th-Order, 10MHz
Butterworth Filter
LOW-POWER xDSL TRANSCEIVER
INTERFACE
With four amplifiers available, the quad OPA4820 can
meet the needs for both differential driver and receiver in
a low-power xDSL line interface design. A simplified
design example is shown on the front page. Two amplifiers
are used as a noninverting differential driver while the
other two implement the driver echo cancellation and
receiver amplifier function. This example shows a single
+12V design where the drive side is taking a 2V
PP
maximum input from the transmit filter and providing a
differential gain of 7, giving a maximum 14V
PP
differential
output swing. This is coupled through 50Ω matching
resistors and a 1:1 transformer to give a maximum 7V
PP
on a 100Ω line. This 7V
PP
corresponds to a 10dBm line
power with a 3.5 crest factor.