8

EL4450C

Wideband Four-Quadrant Multiplier

not possible, one can insert series resistors of around to

51¾ to de-Q the inputs.

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 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.

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:

where

For instance, the EL4450C draws a maximum of 18 mA.

±5V supplies is 180 mW. The maximum supply voltage

parameters is

The maximum dissipation a package can offer is

150°C for reliability, less to retain optimum electrical

performance

cial and 85°C for industrial range

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-

mu m amb i en t t e m p er at ure o f 8 5 °C, t h e 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.

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.

D44450B.fm Page 8 Tuesday, April 21, 1998 9:51 AM