Datasheet

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
715V 715V
1mF
2
11
1mF
715V 715V
3
715V 715V
1mF
V
IN
715V 715V
R
L2
V
OUT
1
4
715V
10kV
9kV
1kV
+3V
1mF
R
L1
V
OUT
+
Figure 59. Single 3 V Supply Differential Line Driver
with 2 V Swing
10
90
100
0%
1V
1V
50ns
V
IN
V
OUT
+
– V
OUT
Figure 60. Differential Driver Pulse Response (V
S
= 3 V,
R
L1
= R
L2
= 200
)
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 100M10M
FREQUENCY – Hz
–50
–30
–40
–60
–70
–80
–90
FEEDTHROUGH – dB
–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
CLOSED-LOOP GAIN – dB
0
–45
–90
–135
PHASE SHIFT – Degrees
–180
GAIN
PHASE
Figure 58. 3:1 Mux ON Channel Gain and Phase vs.
Frequency