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

2

1

0

–4

–5

6

–2

–70

–65

–60

–55

–50

–45

–1

INPUT POWER – dBm

–6

–8

4

5

–3

G = +2

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

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