EL2099C
Video Distribution Amplifier
g
18V, and decrease slightly as supplies are re-
duced to
Applications Information
g
curves. It is not necessary to use equal value split
5V, as shown in the characteristic
Product Description
b
b
supplies. For example, 5V and 12V would be
fine for 0V to 1V video signals.
The EL2099C is a current mode feedback amplifi-
er that has high output current drive capability.
It is built using Elantec’s proprietary dielectric
isolation process that produces NPN and PNP
complimentary transistors. The high output cur-
rent can be useful to drive many standard video
loads in parallel, as well as digital sync pulses
that are 8V or greater.
Good power supply bypassing should be used to
reduce the risk of oscillation. A 1 mF to 10 mF
tantalum capacitor in parallel with a 0.1 mF ce-
ramic capacitor is recommended for bypassing
each supply pin. They should be kept as close as
possible to the device pins.
a
Input Resistor Value
Due to the internal construction of the TO-220
package, the tab of the EL2099C is connected to
a
A small value resistor located in the Input lead
is necessary to keep the EL2099C from oscillat-
ing under certain conditions. A 50X resistor is
recommended for all applications, although
smaller values will work under some circum-
stances. All tests listed in this datasheet are per-
the V
pin. Therefore, care must be taken to
b
S
avoid connecting the tab to the ground plane of
the system.
Printed Circuit Board Layout
a
formed with 50X in the Input lead, as well as
As with any high frequency device, good printed
circuit board layout is necessary for optimum
performance. Ground plane construction is high-
ly recommended. Lead lengths should be as short
as possible. For good AC performance, parasitic
capacitances should be kept to a minimum, espe-
cially at the inverting input, which is sensitive to
stray capacitance. This implies keeping the
ground plane away from this pin. Metal film and
carbon resistors are both acceptable, while use of
wire-wound resistors is not recommended be-
cause of their parasitic inductance. Similarly, ca-
pacitors should be low inductance for best per-
formance.
all typical performance curves. The 50X resistor
a
along with the
Input bias current creates an
additional typical Offset Voltage of only 250 mV
e
temperature variations.
at T
25 C, and a maximum of 1.25 mV over
§
Feedback Resistor Values
The EL2099C has been designed and specified
e
e a
with R
510X and A
2. This value of
F
V
feedback resistor yields extremely flat frequency
response with little to no peaking. However, 3 dB
bandwidth is reduced somewhat because of this.
Wider bandwidth, at the expense of slight peak-
ing, can be accomplished by reducing the value of
the feedback resistor. For example, at a gain of
Driving Cables and Capacitive Loads
The EL2099C was designed with driving multi-
ple coaxial cables in mind. With 440 mA of out-
put drive and low output impedance, driving six
a
2, reducing the feedback resistor to 330X in-
b
creases the 3 dB bandwidth to 70 MHz with
3 dB of peaking. Inversely, larger values of feed-
back resistor will cause roll off to occur at a lower
frequency. There is essentially no peaking with
g
75X double terminated coaxial cables to 11V
with one EL2099C is practical.
l
R
F
510X.
When used as a cable driver, double termination
is always recommended for reflection-free per-
formance. For those applications, the back termi-
nation series resistor will decouple the EL2099C
from the capacitive cable and allow extensive ca-
pacitive drive. For a discussion on some of the
other ways to drive cables, see the application
section on driving cables in the EL2003 data
sheet.
Power Supplies
The EL2099C may be operated with single or
g
split supplies as low as 5V (10V total) to as
high as 18V (36V total). Bandwidth and slew
g
e
g
rate are almost constant from V
10V to
S
10
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