ZXFV202N8EV
SINGLE CHANNEL VIDEO AMPLIFIER EVALUATION BOARD
Evaluation board description
The wide bandwidth of the ZXFV202 video amplifier
necessitates some care in the layout of the printed
circuit. For this reason Zetex has made available an
Evaluation Board.
The Evaluation Board layout serves as a useful
example for many applications, showing a practical
implementation of the advice given below.
Figures 1, 2 and 3 show the schematic and copper
layout of a double-sided printed circuit board suitable
for evaluation of the device in the laboratory.
BNC connector sockets allow connection to test
instruments via 50 cables. The output circuit includes
a resistor matching circuit to present a load of 150 to
the amplifier (equivalent to a 75 back-terminated
video line) and simultaneously provide 50 output
impedance.
The attenuation of this matching circuit is 15.45 dB. As
the amplifier is configured for a voltage gain of 2, the
overall gain is:
6 - 15.45 = -9.45dB.
PCB design
A continuous ground plane is required under the
device and its signal connection paths, to provide the
shortest possible ground return paths for signals and
power supply filtering.
A double-sided or multi-layer PCB construction is
required, with plated-through via holes providing
closely spaced low-inductance connections from some
components to the continuous ground plane (some of
these holes are not visible in the figures for the
Evaluation Board 鈥?artworks and NC drill output can be
provided if required).
Power supply filtering
For the power supply filtering, low inductance surface
mount capacitors are normally required. It has been
found that very good RF decoupling is provided on
each supply using a 1000pF NPO size 0805 or smaller
ceramic surface mount capacitor, closest to the device
pin, with an adjacent 0.1碌F X7R capacitor. Other
configurations are possible and it may be found that a
single 0.01uF X7R capacitor on each supply gives good
results. However this should be supported by larger
decoupling capacitors elsewhere on the printed circuit
board. Values of 1 to 10 碌F are recommended,
particularly where the voltage regulators are located
more than a few inches from the device. These larger
capacitors are recommended to be solid tantalum
electrolytic or ceramic types.
A parts list is provided on the next page.
Figure 1 Circuit schematic
ISSUE 1 - MAY 2004
1
SEMICONDUCTORS
1
2
