AD8002ARMZ(2015) View Datasheet(PDF) - Analog Devices
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AD8002ARMZ Datasheet PDF : 21 Pages
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Data Sheet
DRIVING CAPACITIVE LOADS
The AD8002 was designed primarily to drive nonreactive loads.
If driving loads with a capacitive component is desired, the best
frequency response is obtained by the addition of a small series
resistance as shown in Figure 50.
909Ω
RSERIES
IN
RL
500Ω
CL
Figure 50. Driving Capacitive Loads
Figure 51 shows the optimum value for RSERIES vs. capacitive
load (CL). It is worth noting that the frequency response of the
circuit when driving large capacitive loads is dominated by
the passive roll-off of RSERIES and CL.
40
30
20
10
0
0
5
10
15
20
25
CL (pF)
Figure 51. Recommended RSERIES vs. Capacitive Load
COMMUNICATIONS
Distortion is a key specification in communications applica-
tions. Intermodulation distortion (IMD) is a measure of the
ability of an amplifier to pass complex signals without the
generation of spurious harmonics. Third-order products are
usually the most problematic because several of them fall
near the fundamentals and do not lend themselves to filtering.
Theory predicts that the third-order harmonic distortion
components increase in power at three times the rate of the
fundamental tones. The specification of the third-order intercept
as the virtual point where fundamental and harmonic power
are equal is one standard measure of distortion performance.
Op amps used in closed-loop applications do not always obey
this simple theory. Figure 52 shows the AD8002 performance
summarized at a gain of +2. Here, the worst third-order
products are plotted vs. input power. The third-order intercept
of the AD8002 is 33 dBm at 10 MHz.
AD8002
–45
G = +2
–50
f1 = 10MHz
f2 = 12MHz
–55
–60
–65
2f2 – f1
2f1 – f2
–70
–75
–80
–8 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6
INPUT POWER (dBm)
Figure 52. Third-Order IMD vs. Input Power; f1 = 10 MHz, f2 = 12 MHz
OPERATION AS A VIDEO LINE DRIVER
The AD8002 has been designed to offer good performance as a
video line driver. The important specifications of differential
gain (0.01%) and differential phase (0.02°) meet the most
exacting HDTV demands for driving one video load with each
amplifier. The AD8002 also drives four back terminated loads
(two each), as shown in Figure 53, with equally impressive
performance (0.01%, 0.07°). Another important consideration
is isolation between loads in a multiple load application. The
AD8002 has more than 40 dB of isolation at 5 MHz when
driving two 75 Ω back terminated loads.
750Ω
750Ω
+VS 4.7µF
+
0.1µF
75Ω
75Ω CABLE
VOUT 1
75Ω
8
2
1/2
AD8002 1
3
0.1µF
4
75Ω
75Ω CABLE
VOUT 2
75Ω
75Ω
CABLE
VIN
75Ω
4.7µF
–VS
+
750Ω
5
1/2
AD8002 7
6
750Ω
75Ω
75Ω CABLE
VOUT 3
75Ω
75Ω
75Ω CABLE
VOUT 4
75Ω
Figure 53. Video Line Driver
Rev. E | Page 15 of 21
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