AD9631-EB datasheet(15/20 Pages) AD

15 / 20 page

AD9631/AD9632

REV. A

–15–

APPLICATIONS

The AD9631 and AD9632 are voltage feedback amplifiers well

suited for such applications as photodetectors, active filters, and

log amplifiers. The devices’ wide bandwidth (320 MHz), phase

margin (65

°), low noise current (2.0 pA/√Hz), and slew rate

(1300 V/

µs) give higher performance capabilities to these appli-

cations over previous voltage feedback designs.

With a settling time of 16 ns to 0.01% and 11 ns to 0.1%, the

devices are an excellent choice for DAC I/V conversion. The

same characteristics along with low harmonic distortion make

them a good choice for ADC buffering/amplification. With su-

perb linearity at relatively high signal frequencies, the AD9631

and AD9632 are ideal drivers for ADCs up to 12 bits.

Operation as a Video Line Driver

The AD9631 and AD9632 have been designed to offer out-

standing performance as video line drivers. The important

specifications of differential gain (0.02%) and differential phase

(0.02

°) meet the most exacting HDTV demands for driving

video loads.

Ω

CABLE

274

Ω

274

Ω

CABLE

Ω

OUT

–V

Ω

0.1

µF

AD9631/

AD9632

0.1

µF

Figure 62. Video Line Driver

Active Filters

The wide bandwidth and low distortion of the AD9631 and

AD9632 are ideal for the realization of higher bandwidth active

filters. These characteristics, while being more common in many

current feedback op amps, are offered in the AD9631 and AD9632

in a voltage feedback configuration. Many active filter configu-

rations are not realizable with current feedback amplifiers.

A multiple feedback active filter requires a voltage feedback

amplifier and is more demanding of op amp performance than

other active filter configurations such as the Sallen-Key. In

general, the amplifier should have a bandwidth that is at least

ten times the bandwidth of the filter if problems due to phase

shift of the amplifier are to be avoided.

Figure 63 is an example of a 20 MHz low pass multiple feed-

back active filter using an AD9632.

154

Ω

50pF

100pF

154

Ω

AD9632

78.7

Ω

0.1

µF

+5V

–5V

0.1

µF

100

Ω

OUT

µF

Figure 63. Active Filter Circuit

Choose:

FO = Cutoff Frequency = 20 MHz

α = Damping Ratio = 1/Q = 2

H = Absolute Value of Circuit Gain =

–R4

= 1

Then:

= 2 π F

O C1

4 C1(H

+1)

α2

= α

2 HK

2 K (H

+1)

= H(R1)

AD9631-EB Datasheet(PDF) 15 Page - Analog Devices

AD9631-EB Datasheet(HTML) 15 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL