AD811 Analog Devices, AD811 Datasheet - Page 14

• Manufacturer Part Number: AD811
• Description: High Performance Video Op Amp
• Manufacturer: Analog Devices

Specifications of AD811

• -3db Bandwidth: 140MHz
• Slew Rate: 2.5kV/µs
• Vos: 500µV
• Ib: 2µA
• # Opamps Per Pkg: 1
• Input Noise (nv/rthz): 1.9nV/rtHz
• Vcc-vee: 9V to 36V
• Isy Per Amplifier: 16mA
• Packages: DIP,LCC,SOIC

AD811
OPERATION AS A VIDEO LINE DRIVER
The AD811 has been designed to offer outstanding perform-
ance at closed-loop gains of +1 or greater, while driving
multiple reverse-terminated video loads. The lowest differential
gain and phase errors are obtained when using ±15 V power
supplies. With ±12 V supplies, there is an insignificant increase
in these errors and a slight improvement in gain flatness.
Due to power dissipation considerations, ±12 V supplies are
recommended for optimum video performance. Excellent
performance can be achieved at much lower supplies as well.
The closed-loop gain versus the frequency at different supply
voltages is shown in Figure 43. Figure 44 is an oscilloscope
photograph of an AD811 line driver’s pulse response with ±15 V
supplies. The differential gain and phase error versus the supply
are plotted in Figure 45 and Figure 46, respectively.
Another important consideration when driving multiple cables
is the high frequency isolation between the outputs of the
cables. Due to its low output impedance, the AD811 achieves
better than 40 dB of output-to-output isolation at 5 MHz
driving back-terminated 75 Ω cables.
V
IN
75Ω CABLE
12
–3
–6
9
6
3
0
649Ω
1
Figure 42. A Video Line Driver Operating at a Gain of +2
75Ω
Figure 43. Closed-Loop Gain vs. Frequency, Gain = +2
G = +2
R
R
L
G
= 150Ω
= R
0.1µF
2
3
FB
–
+
AD811
–V
+V
649Ω
4
7
FREQUENCY (MHz)
S
S
10
0.1µF
6
75Ω
75Ω
V
R
S
FB
75Ω CABLE
75Ω CABLE
= ±5V
= 562Ω
V
R
S
FB
= ±15V
100
= 649Ω
75Ω
75Ω
V
V
OUT
OUT
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No. 2
Rev. E | Page 14 of 20
V
V
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
OUT
IN
0
0
Figure 44. Small Signal Pulse Response, Gain = +2, V
5
5
100
90
10
0%
Figure 46. Differential Phase Error vs. Supply Voltage for
a
Figure 45. Differential Gain Error vs. Supply Voltage for
b
6
6
a
b
1V
1V
7
7
the Video Line Driver of Figure 42
the Video Line Driver of Figure 42
8
8
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
9
9
a. DRIVING A SINGLE, BACK-
b. DRIVING TWO PARALLEL, BACK-
a. DRIVING A SINGLE, BACK-
b. DRIVING TWO PARALLEL, BACK-
TERMINATED, 75Ω COAX CABLE
TERMINATED, COAX CABLES
TERMINATED, 75Ω COAX CABLE
TERMINATED, COAX CABLES
10
10
11
11
R
F
100 IRE
MODULATED RAMP
R
F
100 IRE
MODULATED RAMP
12
12
C
C
F
F
= 649Ω
= 3.58MHz
= 649Ω
= 3.58MHz
10ns
13
13
S
14
14
= ±15 V
15
15