Datasheet AD8013 (Analog Devices) - 10

AD8013 RF
As noted in the warning under “Maximum Power Dissipation,”
+V 1.0µF S
a high level of input overdrive in a high noninverting gain circuit
0.1µF
can result in a large current flow in the input stage. Though this
RG 4
current is internally limited to about 30 mA, its effect on the
15
Ω
AD8013 V
total power dissipation may be significant.
1.0µF O R V 11 S C IN L High Performance Video Line Driver 0.1µF RT
At a gain of +2, the AD8013 makes an excellent driver for a
–VS
back terminated 75 Ω video line (Figures 31, 32, and 33). Low differential gain and phase errors and wide 0.1 dB bandwidth Figure 28. Circuit for Driving a Capacitive Load can be realized. The low gain and group delay matching errors ensure excellent performance in RGB systems. Figures 34 and
Table II. Recommended Feedback and Series Resistors vs.
35 show the worst case matching.
Capacitive Load and Gain R R R G F S – Ohms C +V L – pF RF – Ohms G = 2 G
≥
3 S 0.1µF
20 2k 25 15
75
Ω
4 CABLE
50 2k 25 15
75 75
Ω Ω
CABLE AD8013 V
100 3k 20 15
OUT V 11 0.1µF 75
Ω
IN
200 4k 15 15
75
Ω 300 6k 15 15
–VS
≥500 7k 15 15 Figure 31. A Video Line Driver Operating at a Gain of +2
500mV
(R
50ns
F = RG from Table I)
100 90 VIN G = +2 R 0 L = 150
Ω
PHASE V –90 S =
±
5V V +1 S = +5V –180 10 V 0 –270 OUT 0% GAIN –1 PHASE SHIFT – Degrees 1V VS =
±
5V –2 –3
Figure 29. Pulse Response Driving a Large Load Capacitor.
VS = +5V
C
–4
L = 300 pF, G = +2, RF = 6k, RS = 15 Ω
CLOSED-LOOP GAIN (NORMALIZED) – dB –5 Overload Recovery
The three important overload conditions are: input common-
–61M 10M 100M 1G
mode voltage overdrive, output voltage overdrive, and input
FREQUENCY – Hz
current overdrive. When configured for a low closed-loop gain, the amplifier will quickly recover from an input common- Figure 32. Closed-Loop Gain & Phase vs. Frequency mode voltage overdrive; typically in under 25 ns. When con- for the Line Driver figured for a higher gain, and overloaded at the output, the recovery time will also be short. For example, in a gain of +10,
G = +2 R
with 15% overdrive, the recovery time of the AD8013 is about
L = 150
Ω
+0.2
20 ns (see Figure 30). For higher overdrive, the response is somewhat slower. For 6 dB overdrive, (in a gain of +10), the
+0.1
recovery time is about 65 ns.
0 –0.1 VS =
±
5V 500mV 50ns –0.2 V 100 S = +5V V –0.3 90 IN –0.4 NORMALIZED GAIN – dB –0.5 1M 10M 100M 1G V 10 OUT FREQUENCY – Hz 0% 5V
Figure 33. Fine-Scale Gain Flatness vs. Frequency, G = +2, RL = 150 Ω Figure 30. 15% Overload Recovery, G = +10 (RF = 300 Ω, RL = 1 kΩ, VS = ±5 V) –10– REV. A