OPA4820 Datasheet, PDF (17/35 Pages) Texas Instruments – Quad, Unity-Gain Stable, Low-Noise, Voltage-Feedback Operational Amplifier

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OPA4820
SBOS317D − SEPTEMBER 2004 − REVISED AUGUST 2008
3.0
V_IN = 0V to 0.5V
+V_OUT
2.5
R_G = 402Ω
2.0
1.5
1.0
− V_OUT
0.5
0
Time (10ns/div)
Figure 8. Pulse Response for Figure 7 Schematic
161Ω
121Ω
100pF
1/4
OPA4820
77Ω
294Ω
100pF
+5V
1/4
OPA4820
V_O/V_I = 4V/V
f_−3dB = 10MHz
P_D = 225mW
250Ω
V_I
50pF ^500Ω
250Ω
250Ω
50pF ^500Ω
V_O
250Ω
161Ω
121Ω
1/4
OPA4820
100pF
77Ω
294Ω
1/4
OPA4820
−5V
100pF
G_D = 2, ω_O = 2π 10MHz, Q = 1.31
G_D = 2, ω_O = 2π 10MHz, Q = 0.54
Figure 9. Low-Power, Differential I/O, 4th-Order Butterworth Active Filter
15
12
9
6
3
0
−3
−6
−9
1
10
100
Frequency (MHz)
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.
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