AD810

REV. A

–14–

2:1 VIDEO MULTIPLEXER

The outputs of two AD810s can be wired together to form a

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

Figure 54 shows a recommended configuration which 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.

10

90

100

0%

5V

500mV

500nS

Figure 52. Channel Switching Time for the 2:1 Mux

–40

–90

1

10

100

–70

–80

–60

–50

FREQUENCY – MHz

Figure 53. 2:1 Mux OFF Channel Feedthrough vs.

Frequency

AD810

7

3

2

3

0.1µF

+5V

6

750

Ω

–5V

4

0.1µF

8

75

Ω

75

Ω

CABLE

74HC04

AD810

7

3

2

3

0.1µF

+5V

6

–5V

4

0.1µF

8

75

Ω

750

Ω

750

Ω

750

Ω

75

Ω

75

Ω

Figure 54. A Fast Switching 2:1 Video Mux

–0.5

–3.0

1

10

100

–1.0

–1.5

–2.0

–2.5

0

0.5

0

–45

–90

–135

–180

–225

–270

PHASE

GAIN

FREQUENCY – MHz

Figure 55. 2:1 Mux ON Channel Gain and Phase vs.

Frequency