el5397a Intersil Corporation, el5397a Datasheet - Page 13

• Manufacturer Part Number: el5397a
• Description: Triple 200mhz Fixed Gain Amplifier With Enable
• Manufacturer: Intersil Corporation

an AC-coupled, gain of +2, +5V single supply circuit
configuration.
Video Performance
For good video performance, an amplifier is required to
maintain the same output impedance and the same
frequency response as DC levels are changed at the output.
This is especially difficult when driving a standard video load
of 150Ω, because of the change in output current with DC
level. Previously, good differential gain could only be
achieved by running high idle currents through the output
transistors (to reduce variations in output impedance.)
These currents were typically comparable to the entire 4mA
supply current of each EL5397A amplifier. Special circuitry
has been incorporated in the EL5397A to reduce the
variation of output impedance with current output. This
results in dG and dP specifications of 0.03% and 0.04°, while
driving 150Ω at a gain of 2.
Video performance has also been measured with a 500Ω
load at a gain of +1. Under these conditions, the EL5397A
has dG and dP specifications of 0.03% and 0.04°,
respectively.
Output Drive Capability
In spite of its low 4mA of supply current, the EL5397A is
capable of providing a minimum of ±95mA of output current.
With a minimum of ±95mA of output drive.
Driving Cables and Capacitive Loads
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, the back-termination series resistor will
decouple the EL5397A from the cable and allow extensive
capacitive drive. However, other applications may have high
capacitive loads without a back-termination resistor. In these
applications, a small series resistor (usually between 5Ω and
50Ω) can be placed in series with the output to eliminate
most peaking.
0.1µF
V
IN
0.1µF
400
1k
1k
FIGURE 4.
+5
13
+
-
+5
400
V
OUT
EL5397A
Current Limiting
The EL5397A has no internal current-limiting circuitry. If the
output is shorted, it is possible to exceed the Absolute
Maximum Rating for output current or power dissipation,
potentially resulting in the destruction of the device.
Power Dissipation
With the high output drive capability of the EL5397A, it is
possible to exceed the +125°C Absolute Maximum junction
temperature under certain very high load current conditions.
Generally speaking when R
important to calculate the maximum junction temperature
(T
voltages, load conditions, or package type need to be
modified for the EL5397A to remain in the safe operating
area. These parameters are calculated as follows:
where:
PD
PD
where:
T
JMAX
JMAX
T
θ
n = Number of amplifiers in the package
PD
the package
V
I
V
R
SMAX
MAX
MAX
JA
MAX
S
OUTMAX
L
MAX
= Load resistance
= Supply voltage
= Thermal resistance of the package
) for the application to determine if power supply
=
for each amplifier can be calculated as follows:
=
= Maximum ambient temperature
= Maximum supply current
T
2 (
= Maximum power dissipation of each amplifier in
MAX
×
= Maximum output voltage (required)
V
+
S
(
×
θ
JA
I
SMAX
×
n
×
)
+
PD
L
(
falls below about 25Ω, it is
MAX
V
S
- V
)
OUTMAX
)
×
V
--------------------------- -
November 8, 2006
OUTMAX
R
L
FN7197.1