AD813

REV. B

–18–

Single Supply Differential Line Driver

Due to its outstanding overall performance on low supply volt-

ages, the AD813 makes possible exceptional differential trans-

mission on very low power. The circuit of Figure 59 will convert

a single-ended, ground referenced signal to a differential signal

whose common-mode reference is set to one half the supply

voltage. This allows for a greater than 2 V peak-to-peak signal

swing on a single 3 V power supply. A bandwidth over 30 MHz

is achieved with 20 mA of output drive on only 30 mW of quies-

cent power (excluding load current).

+3V

715

715

1 F

2

11

1 F

715

715

3

715

715

1 F

715

715

1

4

715

10k

9k

1k

+3V

1 F

Figure 59. Single 3 V Supply Differential Line Driver

with 2 V Swing

10

90

100

0%

1V

1V

50ns

3:1 Video Multiplexer

Wiring the amplifier outputs together will form a 3:1 mux with

outstanding gain flatness. Figure 55 shows a recommended

configuration which results in –0.1 dB bandwidth of 20 MHz

and OFF channel isolation of 60 dB at 10 MHz on

±5 V sup-

plies. The time to switch between channels is about 180 ns.

Switching time is only slightly affected by signal level.

10

90

100

0%

5V

500mV

500ns

Figure 56. Channel Switching Characteristic for the

3:1 Mux

100k

1M

100M

10M

FREQUENCY – Hz

–50

–30

–40

–60

–70

–80

–90

–20

–10

–100

–110

Figure 57. 3:1 Mux OFF Channel Feedthrough vs.

Frequency

1

10

100

FREQUENCY – MHz

–0.5

–3.0

0.5

0

–1.0

–1.5

–2.0

–2.5

0

–45

–90

–135

–180

GAIN

PHASE

Figure 58. 3:1 Mux ON Channel Gain and Phase vs.

Frequency