Datasheet AD828 (Analog Devices) - 11

AD828 A 3 IN 3 BIN R R Z Z 510 1/2 1/2 510 1 1 AD828 AD828 2 2 510 100FT 510 RG59A/U 510 RZ = 75 510 536 536 6 6 1/2 1/2 BOUT 7 AD828 7 A AD828 OUT 5 5
Figure 6. Bidirectional Transmission CKT
Full-Duplex Transmission
clearly show that each input signal appears undisturbed at its out- Superior load handling capability (50 mA min/amp), high put, while the unwanted signal is eliminated at either receiver. bandwidth, wide supply voltage range, and excellent crosstalk The transmitters operate as followers, while the receivers’ gain rejection makes the AD828 an ideal choice for even the most is chosen to take full advantage of the AD828’s unparalleled demanding high speed transmission applications. CMRR. In practice, this gain is adjusted slightly from its The schematic below shows a pair of AD828s configured to theoretical value to compensate for cable nonidealities and losses. drive 100 feet of coaxial cable in a full-duplex fashion. RZ is chosen to match the characteristic impedance of the Two different NTSC video signals are simultaneously applied at cable employed. AIN and BIN and are recovered at AOUT and BOUT, respectively. Finally, although a coaxial cable was used, the same topology This situation is illustrated in Figures 7 and 8. These pictures applies unmodified to a variety of cables (such as twisted pairs often used in telephony).
500mV 500mV 100 100 90 A 90 B IN IN BOUT AOUT 10 10 0% 0% 500mV 10µs 500mV 10µs
Figure 7. A Transmission/B Reception Figure 8. B Transmission/A Reception
A High Performance Video Line Driver +15V
The buffer circuit shown in Figure 9 will drive a back-terminated
0.1 F 1.0 F
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
8 75 VIN 3
phase and gain at the 3.58 MHz NTSC subcarrier frequency.
1/2 1 RT AD828
This level of performance, which meets the requirements for
RBT 75 2 RT 75
high definition video displays and test equipment, is achieved
4 75
using only 7 mA quiescent current/amplifier.
–15V 0.1 F 1.0 F 1k 1k
Figure 9. Video Line Driver REV. C –11–