EL2386C
250 MHz Triple Current Feedback Amp w/Disable
Applications Information Ð Contd.
cial circuitry has been incorporated in the
EL2386C to reduce the variation of output im-
pedance with current output. This results in dG
drive. However, other applications may have
high capacitive loads without a back-termination
resistor. In these applications, a small series resis-
tor (usually between 5X and 50X) can be placed
in series with the output to eliminate most peak-
and dP specifications of 0.05% and 0.05 while
a
§
driving 150X at a gain of 2.
ing. The gain resistor (R ) can then be chosen to
G
Video Performance has also been measured with
a
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 (R ) to reduce the
F
peaking.
a 500X load at a gain of 1. Under these condi-
tions, the EL2386C has dG and dP specifications
of 0.01% and 0.01 respectively while driving
e a
§
500X at A
1.
V
For complete curves, see the Differential Gain
and Differential Phase vs Input Voltage curves.
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
Output Drive Capability
In spite of its low 3 mA of supply current per
amplifier, the EL2386C is capable of providing a
g
output drive level is unprecedented in amplifiers
minimum of
50 mA of output current. This
g
60 mA. A heat sink may be required to keep
the junction temperature below absolute maxi-
mum when an output is shorted indefinitely.
running at these supply currents. With a mini-
g
capable of driving 50X loads to 2.5V, making it
an excellent choice for driving multiple video
loads in RGB applications.
mum 50 mA of output drive, the EL2386C is
g
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 75X video load. Three sine
waves of varying amplitudes and frequencies are
applied to the three inputs, while a 1 of 3 decoder
selects one amplifier to be on at any given time.
Figure 2 shows the resulting output wave form at
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
2386-39
Figure 1
11
ELANTEC [ ELANTEC SEMICONDUCTOR ]
