AD828 Ver la hoja de datos (PDF) - Analog Devices

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Fabricante

AD828

Dual, Low Power Video Op Amp

Analog Devices 

AD828

AIN

510⍀

3

1/2

AD828 1

2

510⍀

536⍀

RZ

510⍀

100FT

RG59A/U

RZ = 75⍀

RZ

510⍀

3

1

1/2

AD828

2

510⍀

BIN

510⍀

536⍀

BOUT

6

1/2

7 AD828

5

6

1/2

AD828 7

5

AOUT

Figure 6. Bidirectional Transmission CKT

Full-Duplex Transmission

Superior load handling capability (50 mA min/amp), high

bandwidth, wide supply voltage range, and excellent crosstalk

rejection makes the AD828 an ideal choice for even the most

demanding high speed transmission applications.

The schematic below shows a pair of AD828s configured to

drive 100 feet of coaxial cable in a full-duplex fashion.

Two different NTSC video signals are simultaneously applied at

AIN and BIN and are recovered at AOUT and BOUT, respectively.

This situation is illustrated in Figures 7 and 8. These pictures

clearly show that each input signal appears undisturbed at its out-

put, while the unwanted signal is eliminated at either receiver.

The transmitters operate as followers, while the receivers’ gain

is chosen to take full advantage of the AD828’s unparalleled

CMRR. In practice, this gain is adjusted slightly from its

theoretical value to compensate for cable nonidealities and losses.

RZ is chosen to match the characteristic impedance of the

cable employed.

Finally, although a coaxial cable was used, the same topology

applies unmodified to a variety of cables (such as twisted pairs

often used in telephony).

100

AIN

90

500mV

100

BIN 90

500mV

BOUT

10

0%

500mV

10µs

Figure 7. A Transmission/B Reception

AOUT

10

0%

500mV

10µs

Figure 8. B Transmission/A Reception

A High Performance Video Line Driver

The buffer circuit shown in Figure 9 will drive a back-terminated

75 Ω video line to standard video levels (1 V p-p) with 0.1 dB

gain flatness to 40 MHz with only 0.05° and 0.01% differential

phase and gain at the 3.58 MHz NTSC subcarrier frequency.

This level of performance, which meets the requirements for

high definition video displays and test equipment, is achieved

using only 7 mA quiescent current/amplifier.

VIN

RT

75⍀

1k⍀

+15V

8

3

1/2

AD828

2

4

0.1␮F

1

1.0␮F

75⍀

RBT

75⍀

–15V

0.1␮F 1.0␮F

RT

75⍀

1k⍀

Figure 9. Video Line Driver

REV. C

–11–

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