AD810 datasheet(19/22 Pages) AD

19 / 22 page

Data Sheet

AD810

Rev. B | Page 19 of 22

2:1 VIDEO MULTIPLEXER

The outputs of two AD810 devices can be wired together to

form a 2:1 mux without degrading the flatness of the gain response.

Figure 59 shows a recommended configuration that results in

−0.1 dB bandwidth of 20 MHz and off channel isolation of

77 dB at 10 MHz on ±5 V supplies. The time to switch between

channels is about 0.75 μs when the DISABLE pins are driven by

open-drain output logic. Adding pull-up resistors to the logic

outputs or using complementary output logic (such as the

74HC04) reduces the switching time to about 180 ns. The

switching time is only slightly affected by the signal level.

100

500mV

500ns

Figure 57. Channel Switching Time for the 2:1 Mux

–40

–90

–85

–80

–75

–70

–65

–60

–55

–50

–45

1100

FREQUENCY (MHz)

Figure 58. Isolation vs. Frequency for 2:1 Mux, Off Channel

750Ω

75Ω

AD810

–5V

+5V 0.1µF

0.1µF

VINA

75Ω

VOUT

75Ω

CABLE

750Ω

75Ω

AD810

–5V

+5V 0.1µF

0.1µF

VINB

VSW

74HC04

Figure 59. A Fast Switching 2:1 Video Mux

–2.5

–1.5

–0.5

–3.0

–2.0

–1.0

0.5

10M

100M

–45

–90

–135

–180

–225

–270

FREQUENCY (Hz)

PHASE

GAIN

VS = ±5V

Figure 60. Closed-Loop Gain and Phase Shift vs. Frequency for 2:1 Mux,

On Channel

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