el5166iwz Intersil Corporation, el5166iwz Datasheet - Page 11

• Manufacturer Part Number: el5166iwz
• Description: 1.4ghz Current Feedback Amplifiers With Enable
• Manufacturer: Intersil Corporation

which spans ±3.2V. The output range of the EL5166 and
EL5167 is also quite large, extending to within 1V of the
supply rail. On a ±5V supply, the output is therefore capable
of swinging from -4V to +4V.
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 8.5mA supply current of each
EL5166 and EL5167 amplifier. Special circuitry has been
incorporated in the EL5166 and EL5167 to reduce the
variation of output impedance with current output. This
results in dG and dP specifications of 0.01% and 0.03°,
while driving 150Ω at a gain of 2.
Output Drive Capability
In spite of their low 8.5mA of supply current, the EL5166 and
EL5167 are capable of providing a minimum of ±110mA of
output current. With so much output drive, the EL5166 and
EL5167 are capable of driving 50Ω loads to both rails,
making them an excellent choice for driving isolation
transformers in telecommunications applications.
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 EL5166 and EL5167 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. The gain resistor (R
then be chosen to make up for any gain loss which may be
created by this additional resistor at the output. In many
cases it is also possible to simply increase the value of the
feedback resistor (R
Current Limiting
The EL5166 and EL5167 have 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 EL5166 and
EL5167, it is possible to exceed the 125°C Absolute
Maximum junction temperature under certain very high load
current conditions. Generally speaking when R
F
) to reduce the peaking.
11
L
falls below
G
EL5166, EL5167
) can
about 25Ω, it is important to calculate the maximum junction
temperature (T
power supply voltages, load conditions, or package type
need to be modified for the EL5166 and EL5167 to remain in
the safe operating area. These parameters are calculated as
follows:
where:
PD
where:
T
PD
JMAX
T
θ
n = Number of amplifiers in the package
PD
the package
V
I
V
R
SMAX
MAX
JA
MAX
MAX
S
OUTMAX
L
MAX
= Load resistance
= Supply voltage
= Thermal resistance of the package
=
for each amplifier can be calculated as follows:
=
= Maximum ambient temperature
= Maximum supply current of 1A
T
= Maximum power dissipation of each amplifier in
2 (
MAX
= Maximum output voltage (required)
×
V
JMAX
+
S
(
×
θ
JA
I
SMAX
) for the application to determine if
×
n PD
×
)
+
(
MAX
V
S
–
)
V
OUTMAX
)
×
V
--------------------------- -
OUTMAX
May 15, 2007
R
L
FN7365.5