EL4450C
EL4450C
Wideband Four-Quadrant Multiplier
not possible, one can insert series resistors of around to
51¾ to de-Q the inputs.
• R
PAR
is the parallel of all resistors loading the output
For instance, the EL4450C draws a maximum of 18 mA.
With light loading, R
PAR
→×
and the dissipation with
±5V supplies is 180 mW. The maximum supply voltage
that the device can run on for a given P
D
and the other
parameters is
V
S
,max = (P
D
+ V
O
2/R
PAR
)/(2I
S
+ V
O
/R
PAR
)
Signal Amplitudes
Signal input common-mode voltage must be between
(V-) + 2.5V and (V+) -2.5V to ensure linearity. Addi-
tionally, the differential voltage on any input stage must
be limited to ± 6V to prevent damage. The differential
signal range is ± 2V in the EL4450C. The input range is
substantially constant with temperature.
The maximum dissipation a package can offer is
P
D
,max = (T
J
,max–T
A
,max)/θ
JA
The Ground Pin
The ground pin draws only 6 µA maximum DC current,
and may be biased anywhere between (V-) +2.5V and
(V+) -3.5V. The ground pin is connected to the IC’s sub-
strate and frequency compensation components. It
serves as a shield within the IC and enhances input stage
CMRR over frequency, and if connected to a potential
other than ground, it must be bypassed.
Where T
J
,max is the maximum junction temperature,
150°C for reliability, less to retain optimum electrical
performance
T
A
,max is the ambient temperature, 70°C for commer-
cial and 85°C for industrial range
θ
JA
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 junction temperature of 150°C and a maxi-
m u m a m b i e n t t e m pe r a t u r e o f 8 5° C , t he 6 5° C
temperature rise and package thermal resistance of
120°/W gives a dissipation of 542 mW at 85°C. This
allows the full maximum operating supply voltage
unloaded, but reduced if loaded significantly.
Power Supplies
The EL4450C works well on supplies from ± 3V to ±
15V. The supplies may be of different voltages as long
as the requirements of the GND pin are observed (see
the Ground Pin section for a discussion). The supplies
should be bypassed close to the device with short leads.
4.7 µF tantalum capacitors are very good, and no smaller
bypasses need be placed in parallel. Capacitors as low as
0.01 µF can be used if small load currents flow.
Single-polarity supplies, such as +12V with +5V can be
used, where the ground pin is connected to +5V and V-
to ground. The inputs and outputs will have to have their
levels shifted above ground to accommodate the lack of
negative supply.
The power dissipation of the EL4450C increases with
power supply voltage, and this must be compatible with
the package chosen. This is a close estimate for the dissi-
pation of a circuit:
P
D
=2*I
S
,max*V
S
+ (V
S
–V
O
)*V
O
/R
PAR
Output Loading
The output stage is very powerful. It typically can source
85 mA and sink 120 mA. 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 delivering the 30 mA continuous output given in
the Absolute Maximum Ratings table in this data sheet,
or higher purely transient currents.
Gain accuracy degrades only 0.2% from no load to 100¾
load. Heavy resistive loading will degrade frequency
response and video distortion for loads < 100¾.
Capacitive loads will cause peaking in the frequency
response. If a capacitive load must be driven, a small-
valued series resistor can be used to isolate it. 12¾ to
51¾ should suffice. A 22¾ series resistor will limit
peaking to 2.5 dB with even a 220 pF load.
where
• I
S
,max is the maximum supply current
• V
S
is the ± supply voltage (assumed equal)
• V
O
is the output voltage
8
ELANTEC [ ELANTEC SEMICONDUCTOR ]
