Datasheet

AD8003
Rev. B | Page 12 of 16
APPLICATIONS INFORMATION
GAIN CONFIGURATIONS
Unlike conventional voltage feedback amplifiers, the feedback
resistor has a direct impact on the closed-loop bandwidth and
stability of the current feedback op amp circuit. Reducing the
resistance below the recommended value can make the amplifier
response peak and can even become unstable. Increasing the
size of the feedback resistor reduces the closed-loop bandwidth.
Table 5 provides a convenient reference for quickly determining
the feedback and gain set resistor values, and the small and
large signal bandwidths for common gain configurations. The
feedback resistors in Table 5 have been optimized for 0.1 dB
flatness frequency response.
Table 5. Recommended Values and Frequency Response
1
Gain R
F
(Ω) R
G
(Ω) R
S
(Ω)
−3 dB
SS BW
(MHz)
Large
Signal
−3 dB
BW
Large
Signal
0.1 dB
BW
−1 300 300 0 734 668 --
+1 432 N/A 24.9 1650 822 --
[phone] 190
[phone] 165
+10 300 33.2 0 446 422 170
1
Conditions: V
S
= ±5 V, T
A
= 25°C, R
L
= 150 Ω.
Figure 38 and Figure 39 show the typical noninverting and inverting
configurations and recommended bypass capacitor values.
FB
AD8003
10µF
0.1µF
R
G
R
S
+V
S
V
O
V
IN
R
L
–
+
V
O
+V
–V
S
–V
10µF
0.1µF
R
F
05721-038
Figure 38. Noninverting Gain
FB
AD8003
10µF
0.1µF
R
G
+V
S
V
O
V
IN
R
L
–
+
V
O
+V
–V
S
–V
10µF
0.1µF
R
F
05721-039
Figure 39. Inverting Gain
RGB VIDEO DRIVER
Figure 40 shows a typical RGB driver application using bipolar
supplies. The gain of the amplifier is set at +2, where R
F
= R
G
=
464 Ω. The amplifier inputs are terminated with shunt 75 Ω
resistors, and the outputs have series 75 Ω resistors for proper
video matching. In Figure 40, the POWER DOWN pins are not
shown connected to any signal source for simplicity. If the power-
down function is not used, it is recommended that the POWER
DOWN pins be tied to the positive supply and not be left floating
(not connected).
In applications that require a fixed gain of +2, as previously
mentioned, the designer may consider the ADA4862-3.
The ADA4862-3 is another high performance triple current
feedback amplifier. The ADA4862-3 has integrated feedback
and gain set resistors that reduce board area and simplify designs.
+V
S
10µF
0.1µF
–V
S
10µF
0.1µF
+V
S
10µF
0.1µF
–V
S
10µF
0.1µF
75Ω
75Ω
G
IN
05721-036
21
22
19
24
R
F
464Ω
75Ω
R
G
464Ω
75Ω
R
IN
PD1
3
2
4
PD2
PD3
1
+V
S
10µF
0.1µF
75Ω
75Ω
B
IN
G
OU
14
23
5
T
R
OUT
B
OUT
–V
S
10µF
0.1µF
6
16
17
15
18
13
R
F
464Ω
R
G
464Ω
20
R
F
464Ω
R
G
464Ω
AD8003
Figure 40. RGB Video Driver