Datasheet

AD8091/AD8092
Rev. C | Page 15 of 20
Some circuits use a sync tip clamp to hold the sync tips at a
relatively constant level to lower the amount of dynamic signal
swing required. However, these circuits can have artifacts like
sync tip compression unless they are driven by a source with a
very low output impedance. The AD8091/AD8092 have
adequate signal swing when running on a single 5 V supply to
handle an ac-coupled composite video signal.
The feedback circuit provides unity gain for the dc biasing of
the input and provides a gain of 2 for any signals that are in the
video bandwidth. The output is ac-coupled and terminated to
drive the line.
The capacitor values provide minimum tilt or field time
distortion of the video signal. These values are required for
video that is considered to be studio or broadcast quality.
However, if a lower consumer grade of video, sometimes
referred to as consumer video, is all that is desired, the values
and the cost of the capacitors can be reduced by as much as a
factor of 5 with minimum visible degradation in the picture.
The input to the circuit shown in
Figure 36 is a standard
composite (1 V p-p) video signal that has the blanking level at
ground. The input network level shifts the video signal by
means of ac coupling. The noninverting input of the op amp is
biased to half of the supply voltage.
02859-036
AD8091
5V
+
4.99kΩ
10µF
47µF
+
4.99kΩ
10kΩ
R
T
75Ω
R
G
1kΩ
R
F
1kΩ
R
BT
75Ω
R
L
75Ω
V
OU
T
C
OMPOSITE
VIDEO IN
+
220µF
0.1µF
3
2
4
6
7
1000µF
0.1µF 10µF
+
Figure 36. Single-Supply Composite Video Line Driver