AD8091_07 Datasheet, PDF (15/20 Pages) Analog Devices – Low Cost, High Speed Rail-to-Rail Amplifiers

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 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.
5V
4.99kΩ
COMPOSITE
VIDEO IN _RT
75Ω
4.99kΩ
+
10µF
47µF
+
10kΩ
3
7
AD8091
+
0.1µF 10µF
1000µF
+
R_BT
75Ω
6
2
4
R_F ^0.1µF
1kΩ
R_G
1kΩ
220µF
V_OUT
R_L
75Ω
Figure 36. Single-Supply Composite Video Line Driver
AD8091/AD8092
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.
Rev. C | Page 15 of 20