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EL2386C
250 MHz Triple Current Feedback Amp wDisable
Applications Information
Contd
cial circuitry has been incorporated in the
EL2386C to reduce the variation of output im-
pedance with current output This results in dG
and dP specifications of 005% and 005 while
driving 150
X at a gain of a2
Video Performance has also been measured with
a 500
X load at a gain of a1 Under these condi-
tions the EL2386C has dG and dP specifications
of 001% and 001
respectively while driving
500
X at AV ea1
For complete curves see the Differential Gain
and Differential Phase vs Input Voltage curves
Output Drive Capability
In spite of its low 3 mA of supply current per
amplifier the EL2386C is capable of providing a
minimum of g50 mA of output current This
output drive level is unprecedented in amplifiers
running at these supply currents With a mini-
mum g50 mA of output drive the EL2386C is
capable of driving 50
X loads to g25V making it
an excellent choice for driving multiple video
loads in RGB applications
Driving Cables and Capacitive Loads
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 EL2386C
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 resis-
tor (usually between 5
X and 50X) can be placed
in series with the output to eliminate most peak-
ing The gain resistor (RG) can 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 val-
ue of the feedback resistor (RF) to reduce the
peaking
Current Limiting
The EL2386C has no internal current-limiting
circuitry If an output is shorted indefinitely the
power dissipation could easily increase such that
the part will be destroyed Maximum reliability
is maintained if the output current never exceeds
g
60 mA A heat sink may be required to keep
the junction temperature below absolute maxi-
mum when an output is shorted indefinitely
Multiplexing with the EL2386C
The ENABLE pins on the EL2386C allow for
multiplexing applications
Figure 1 shows an
EL2386C with all 3 outputs tied together driving
a back terminated 75
X video load Three sine
waves of varying amplitudes and frequencies are
applied to the three inputs whilea1of3 decoder
selects one amplifier to be on at any given time
Figure 2 shows the resulting output wave form at
2386-39
Figure 1
11