Datasheet

REV. D
AD8001
–12–
Communications
Distortion is a key specification in communications applications.
Intermodulation distortion (IMD) is a measure of the ability of
an amplifier to pass complex signals without the generation of
spurious harmonics. The third order products are usually the
most problematic since 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 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. At a gain of +2, the AD8001
has performance summarized in Figure 10. Here the worst third
order products are plotted versus input power. The third order
intercept of the AD8001 is +33 dBm at 10 MHz.
–80
3–7
–75
210–4–5 6–2
–70
–65
–60
–55
–50
–45
–1
THIRD ORDER IMD – dBc
INPUT POWER – dBm
–6–8 4 5–3
2F
2
– F
1
2F
1
– F
2
G = +2
F
1
= 10MHz
F
2
= 12MHz
Figure 10. Third Order IMD; F
1
= 10 MHz, F
2
= 12 MHz
Operation as a Video Line Driver
The AD8001 has been designed to offer outstanding perfor-
mance as a video line driver. The important specifications of
differential gain (0.01%) and differential phase (0.025°) meet
the most exacting HDTV demands for driving one video load.
The AD8001 also drives up to two back terminated loads as
shown in Figure 11, with equally impressive performance (0.01%,
0.07°). Another important consideration is isolation between
loads in a multiple load application. The AD8001 has more
than 40 dB of isolation at 5 MHz when driving two 75 Ω back
terminated loads.
909909
75
CABLE
75
75
V
OUT
NO. 1
V
OUT
NO. 2
+V
S
–V
S
V
IN
0.1F
0.001F
AD8001
0.1F
75
CABLE
75
75
75
CABLE
+
0.001F
75
Figure 11. Video Line Driver