EL4083C Elantec Semiconductor, Inc. (acquired by Intersil), EL4083C Datasheet - Page 9

• Manufacturer Part Number: EL4083C
• Description: Current Mode Four Quadrant Multiplier
• Manufacturer: Elantec Semiconductor, Inc. (acquired by Intersil)

General Operating Information
rameters and to some extent bandwidth while
improving the signal to noise performance feed-
through and control range
The EL4083 is fundamentally different from con-
ventional voltage mode multipliers in that the
available input range can be tailored to accom-
modate voltage sources of almost any size by se-
lecting appropriate input series resistor values If
desired one can interface with voltages that are
much greater than the supplies from which the
part is powered Current source signals can be
connected directly to the multiplier inputs The
parts’ dynamic range can also be tailored to a
large extent for a current signal by the appropri-
ate selection of I
manner as a virtual ground input of an opera-
tional amplifier and thus can serve as a summing
node for any number of voltage and or current
signals Outputs of components such as current
output DACs transconductance amplifiers and
current conveyors can be directly connected to
the inputs
Ideally a multiplier should give zero output if
either one of its multiplying inputs is zero A
nonzero output under these conditions is caused
by a combination of input and output referred
offsets An output referred offset can be thought
of as a fixed value added to the output and thus
only affects D C accuracy An input referred off-
set at a multiplying input allows signal to feed-
through from the other multiplying input to the
output(s) The EL4083 is trimmed during testing
at Elantec for X and Y input referred offset for I
current to each input which nulls the feed-
through caused by internal device mismatches
These current values are ratioed to the value of
I
maintained at different values of I
there will be some mistracking in the trim net-
works so that the input referred null point will
deviate away from zero at values of I
1 6 mA Figure 9 shows optional external input
and output referred offset trim networks which
can be used as needed to improve performance
e
Z
Contd
1 6 mA The internal trim networks provide a
so that the input referred nulls are largely
Z
These inputs act in the same
Z
Z
Current Mode Four Quadrant Multiplier
lower than
However
Z
9
As mentioned the output referred offset only af-
fects D C accuracy which may not be an issue in
A C applications In gain control applications
one may only need to null feedthrough with re-
spect to the gain control input
In gain control (VCA) applications the X input
should be used as the control input and the signal
applied to the Y input since it has slightly higher
bandwidth and better linearity and distortion
performance
Current Outputs (I
and Distortion
Another unique feature of the EL4083 is the dif-
ferential ground referenced current output struc-
ture These outputs can drive 50
lines and reactive loads such as transformers ba-
luns and LC tank and filter circuits directly
Unlike low impedance follower buffers these out-
puts do not interact with the load to produce
ringing or instability If a high level low imped-
ance output is required the outputs can be recov-
ered differentially and converted to a single end-
ed output with a fast op amp such as the EL2075
(see Figure 19) The outputs can also drive cur-
rent input devices such as CMF amps current
conveyors and its own inputs directly by simple
connection
Figures 12 and 14 show the nulled gain and feed-
through characteristics of the I
puts which are virtually identical and differ only
in phase Figure 12 is with the A C signal applied
to the X input with Y used as the gain control
and in Figure 14 these signals are reversed Note
that in both cases the signal feedthrough rolls up
and peaks near the cutoff frequency This is quite
typical of the performance of all previous four
quadrant multipliers Figures 13 and 15 show the
corresponding gain feedthrough characteristics
for the differentially recovered output signal
I
through at high frequencies is lower by more
than 40 dB
XY
See EL2082 Data Sheet Receiver IF Amplifier (Figure 19)
The EL2082 also has a current output
-I
XY
Note that in this case the peak feed-
XY
EL4083C
I
XY
) Feedthrough
XY
and I
terminated
XY
out-