Datasheet AD813 (Analog Devices) - 19

AD813 3:1 Video Multiplexer Single Supply Differential Line Driver
Wiring the amplifier outputs together will form a 3:1 mux with Due to its outstanding overall performance on low supply volt- outstanding gain flatness. Figure 55 shows a recommended ages, the AD813 makes possible exceptional differential trans- configuration which results in –0.1 dB bandwidth of 20 MHz mission on very low power. The circuit of Figure 59 will convert and OFF channel isolation of 60 dB at 10 MHz on ± 5 V sup- a single-ended, ground referenced signal to a differential signal plies. The time to switch between channels is about 180 ns. whose common-mode reference is set to one half the supply Switching time is only slightly affected by signal level. 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-
500mV 500ns
cent power (excluding load current).
100 715
V
715
V
90 VOUT+ 1 +3V
m
F RL1 4 2 +3V 715
V
10 0% 1k
V
1
m
F 715
V
715
V
V 5V IN 1
m
F 1 9k
V
715
V
715
V Figure 56. Channel Switching Characteristic for the
1
m
F 10k
V 3:1 Mux
–10 3 VOUT– –20 11 RL2 –30 –40 715
V
715
V
–50 –60
Figure 59. Single 3 V Supply Differential Line Driver
–70
with 2 V Swing
FEEDTHROUGH – dB –80 –90 1V 50ns –100 100 VIN –110 90 100k 1M 10M 100M FREQUENCY – Hz
Figure 57. 3:1 Mux OFF Channel Feedthrough vs. Frequency
0 10 V + – OUT – VOUT PHASE 0% –45 1V –90 0.5 –135 0 –180
Figure 60. Differential Driver Pulse Response (VS = 3 V,
GAIN PHASE SHIFT – Degrees
RL1 = RL2 = 200 Ω)
–0.5 –1.0 –1.5 –2.0 CLOSED-LOOP GAIN – dB –2.5 –3.0 1 10 100 FREQUENCY – MHz
Figure 58. 3:1 Mux ON Channel Gain and Phase vs. Frequency –18– REV. B