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EL4451C View Datasheet(PDF) - Elantec -> Intersil

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EL4451C Datasheet PDF : 12 Pages
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EL4451C
Wideband Variable-Gain Amplifier Gain of 2
Applications Information Contd
Signal Amplitudes
Signal input common-mode voltage must be be-
tween (Vb)a3V and (Va)b3V to ensure linear-
ity Additionally the differential voltage on any
input stage must be limited to g6V to prevent
damage The differential signal range is g2V in
the EL4451 The input range is substantially con-
stant with temperature
The Ground Pin
The ground pin draws only 6mA maximum DC
current and may be biased anywhere between
(Vb)a2 5V and (Va)b3 5V The ground pin is
connected to the IC’s substrate and frequency
compensation components It serves as a shield
within the IC and enhances input stage CMRR
and feedthrough over frequency and if connected
to a potential other than ground it must be by-
passed
Power Supplies
The EL4451 works with any supplies from g3V
to g15V The supplies may be of different volt-
ages as long as the requirements of the ground
pin are observed (see the Ground Pin section)
The supplies should be bypassed close to the de-
vice with short leads 4 7mF tantalum capacitors
are very good and no smaller bypasses need be
placed in parallel Capacitors as small as 0 01mF
can be used if small load currents flow
Single-polarity supplies such as a12V with
a5V can be used where the ground pin is con-
nected to a5V and Vb to ground The inputs
and outputs will have to have their levels shifted
above ground to accommodate the lack of nega-
tive supply
The power dissipation of the EL4451 increases
with power supply voltage and this must be
compatible with the package chosen This is a
close estimate for the dissipation of a circuit
PD e 2 c VS c IS max a (VS b VO) c VO RPAR
where IS max is the maximum supply current
VS is the g supply voltage (assumed
equal)
VO is the output voltage
RPAR is the parallel of all resistors loading
the output
For instance the EL4451 draws a maximum of
x 18mA With light loading RPAR % and the
dissipation with g5V supplies is 180 mW The
maximum supply voltage that the device can run
on for a given PD and other parameters is
VS max e (PD a VO2 RPAR) (2IS a VO RPAR)
The maximum dissipation a package can offer is
PD max e (TJ maxbTA max) iJA
Where TJ max is the maximum die tempera-
ture 150 C for reliability less to re-
tain optimum electrical performance
TA max is the ambient temperature
70 C for commercial and 85 C for in-
dustrial range
iJA is the thermal resistance of the
mounted package obtained from
data sheet dissipation curves
The more difficult case is the SO-14 package
With a maximum die temperature of 150 C and a
maximum ambient temperature of 85 C the 65 C
temperature rise and package thermal resistance
of 120 C W gives a dissipation of 542 mW at
85 C This allows the full maximum operating
supply voltage unloaded but reduced if loaded
Output Loading
The output stage of the EL4451 is very powerful
It typically can source 80mA and sink 120mA Of
course this is too much current to sustain and
the part will eventually be destroyed by excessive
dissipation or by metal traces on the die opening
The metal traces are completely reliable while de-
livering the 30mA continuous output given in the
Absolute Maximum Ratings table in this data
sheet or higher purely transient currents
Gain changes only 0 2% from no load to 100X
load Heavy resistive loading will degrade fre-
quency response and video distortion for loads
k100X
Capacitive loads will cause peaking in the fre-
quency response If capacitive loads must be driv-
en a small-valued series resistor can be used to
isolate it 12X to 51X should suffice A 22X series
resistor will limit peaking to 2 5 dB with even a
220pF load
8
 

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