Datasheet
ADA4861-3
Rev. A | Page 14 of 16
05708-004
75Ω
CABLE
75Ω
CABLE
75Ω
75Ω
75Ω
V
OUT
2
V
OUT
1
–V
S
+V
S
V
IN
0.1µF
0.1µF
10µF
10µF
75Ω
CABLE
75Ω
75Ω
+
–
R
F
301Ω
R
G
301Ω
ADA4861-3
RGB VIDEO DRIVER
Figure 50 shows a typical RGB driver application using bipolar
supplies. The gain of the amplifier is set at +2, where R
F
= R
G
=
301 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 50, 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 negative supply and not be left
floating (not connected).
For applications that require a fixed gain of +2, consider using
the
Figure 51. Video Driver Schematic for Two Video Loads
ADA4862-3 with integrated R
F
and R
G.
The ADA4862-3 is
another high performance triple current feedback amplifier that
can simplify design and reduce board area.
0.1
–0.9
–0.8
–0.7
–0.6
–0.5
–0.4
–0.3
–0.2
–0.1
0
1 10 100 400
05708-010
NORMALIZED GAIN (dB)
FREQUENCY (MHz)
V
S
= ±5V
R
L
= 75Ω
V
OUT
= 2V p-p
R
F
301Ω
R
G
301Ω
75Ω
75Ω
V
OUT
(R)
V
IN
(R)
7
5
6
R
F
301Ω
R
G
301Ω
75Ω
75Ω
V
OUT
(G)
V
IN
(G)
8
10
9
R
F
301Ω
R
G
301Ω
75Ω
75Ω
V
OUT
(B)
V
IN
(B)
14
12
13
123
10µF
0.1µF
+
V
S
4
0.1µF
10µF
–V
S
11
PD1
PD2
PD3
05708-003
Figure 52. Large Signal Frequency Response for Various Supplies, R
L
= 75 Ω
POWER-DOWN PINS
The ADA4861-3 is equipped with three independent POWER
DOWN pins, one for each amplifier. This allows the user the
ability to reduce the quiescent supply current when an amplifier
is inactive. The power-down threshold levels are derived from
the voltage applied to the −V
S
pin. When used in single-supply
applications, this is especially useful with conventional logic
levels. The amplifier is powered down when the voltage applied
to the POWER DOWN pins is greater than −V
S
+ 1 V. In a
single-supply application, this is > +1 V (that is, 0 V + 1 V), in a
±5 V supply application, the voltage is > −4 V. The amplifier is
enabled whenever the POWER DOWN pins are left either open
or the voltage on the POWER DOWN pins is lower than 1 V
above −V
S
. If the POWER DOWN pins are not used, it is best to
connect them to the negative supply.
Figure 50. RGB Video Driver
DRIVING TWO VIDEO LOADS
In applications that require two video loads be driven
simultaneously, the ADA4861-3 can deliver.
Figure 51 shows
the ADA4861-3 configured with dual video loads.
Figure 52
shows the dual video load 0.1 dB bandwidth performance.