EL4451C
Wideband Variable-Gain Amplifier, Gain of 2
For instance, the EL4451 draws a maximum of
%
g
dissipation with 5V supplies is 180 mW. The
maximum supply voltage that the device can run
Applications Information Ð Contd.
18mA. With light loading, RPAR x and the
Signal Amplitudes
Signal input common-mode voltage must be be-
on for a given P and other parameters is
D
b a
a b
) 3V to ensure linear-
ity. Additionally, the differential voltage on any
tween (V
)
3V and (V
2
e
a
a
) / (2I V
S
V , max
S
(P
D
V
/R
PAR
/R )
O PAR
O
g
input stage must be limited to 6V to prevent
damage. The differential signal range is 2V in
g
The maximum dissipation a package can offer is
the EL4451. The input range is substantially con-
stant with temperature.
e
b
T
A
P
, max
D
(T , max
J
, max) / i
JA
Where T , max is the maximum die tempera-
J
The Ground Pin
The ground pin draws only 6mA maximum DC
current, and may be biased anywhere between
ture, 150 C for reliability, less to re-
tain optimum electrical performance
§
T , max is the ambient temperature,
A
b a
)
a b
(V
2.5V and (V
) 3.5V. The ground pin is
70 C for commercial and 85 C for in-
dustrial range
§
§
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.
i
is the thermal resistance of the
mounted package, obtained from
data sheet dissipation curves
JA
The more difficult case is the SO-14 package.
With a maximum die temperature of 150 C and a
§
Power Supplies
The EL4451 works with any supplies from 3V
maximum ambient temperature of 85 C, the 65 C
§
§
g
to 15V. The supplies may be of different volt-
temperature rise and package thermal resistance
of 120 C/W gives a dissipation of 542 mW at
g
§
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.
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.
a
5V can be used, where the ground pin is con-
Single-polarity supplies, such as
a
nected to
12V with
a
b
5V and V 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:
Gain changes only 0.2% from no load to 100X
load. Heavy resistive loading will degrade fre-
quency response and video distortion for loads
k
100X.
e
c
c
a
b
c
) V
O
P
2
V
I , max
S
(V
S
V
/R
O PAR
D
S
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.
where I , max is the maximum supply current
S
g
supply voltage (assumed
V
is the
S
equal)
V
O
is the output voltage
R
is the parallel of all resistors loading
PAR
the output
8
ELANTEC [ ELANTEC SEMICONDUCTOR ]
