REV. B

AD826

–12–

SINGLE-ENDED TO DIFFERENTIAL LINE DRIVER

Outstanding CMRR (> 80 dB @ 5 MHz), high bandwidth, wide

supply voltage range, and the ability to drive heavy loads, make

the AD826 an ideal choice for many line driving applications.

In this application, the AD830 high speed video difference

amp serves as the differential line receiver on the end of a back

terminated, 50 ft., twisted-pair transmission line (see Figure 40).

The overall system is configured in a gain of +1 and has a –3 dB

bandwidth of 14 MHz. Figure 39 is the pulse response with a

2 V p-p, 1 MHz signal input.

10

90

100

0%

2V

200ns

2V

Figure 39. Pulse Response

15V

1/2

AD826

0.01 F

2.2 F

1/2

AD826

36

1.05k

5pF

BNC

–15V

AD830

50 FEET TWISTED PAIR

Z = 72

36

0.1 F

1.05k

5pF

1.05k

1.05k

0.1 F

0.01 F

2.2 F

36

36

15V

0.01 F

0.1 F

–15V

0.1 F

0.01 F

Figure 40. Differential Line Driver

LOW DISTORTION LINE DRIVER

The AD826 can quickly be turned into a powerful, low distor-

tion line driver (see Figure 41). In this arrangement the AD826

can comfortably drive a 75

Ω back-terminated cable, with a

5 MHz, 2 V p-p input; all of this while achieving the harmonic

distortion performance outlined in the following table.

Configuration

2nd Harmonic

1. No Load

–78.5 dBm

2. 150

–63.8 dBm

3. 150

Ω R

Ω R

C

–70.4 dBm

In this application one half of the AD826 operates at a gain of

2.1 and supplies the current to the load, while the other pro-

vides the overall system gain of 2. This is important for two

reasons: the first is to keep the bandwidth of both amplifiers the

same, and the second is to preserve the AD826’s ability to oper-

be chosen to satisfy the following equation:

1.1k

1k

1k

1/2

AD826

1/2

AD826

7.5

1k

75

75

75

1 F

0.1 F

0.1 F

1 F

Figure 41. Low Distortion Amplifier