AD9100

REV. B

–9–

In the FFT spectrum below (see Figure 19), the 71.4 MHz IF is

observed at 1.4 MHz. Note that the highest frequency observed

(FS/2) is determined by the sample rate of the T/H.

0

–100

5.0

–80

DC

–40

–60

–20

4.0

3.0

2.0

1.0

FREQUENCY – MHz

78

6

8

2

5

3

4

Figure 19. 71.4 MHz Signal Sampled at 10 MSPS with

200 mV p-p Input

Low Noise Applications

When processing low level single event signals in which noise

performance is the primary concern, amplification ahead of the

AD9100 can increase overall system signal to noise ratio. Front-

end amplification often results in an increase in hold mode

distortion levels because of the track mode limitations of the

amplifier which is used. Depending on the signal levels and

bandwidth, the AD9618 low noise high gain amplifier is a pos-

sible candidate for this application. See Figure 20.

As a general rule, if the goal is maximize SNR (minimize noise),

pre-AD9100 amplification is recommended. When the system

goal is to maximize the spurious free dynamic range (minimize

distortion), post-AD9100 amplification is recommended.

AD9618

LOW

LEVEL

SOURCE

TO

ENCODER

AD9100

Figure 20. Using AD9618 as Pre-Amp for AD9100