EL4083CS INTERSIL [Intersil Corporation], EL4083CS Datasheet - Page 7

• Manufacturer Part Number: EL4083CS
• Description: Current Mode Four Quadrant Multiplier
• Manufacturer: INTERSIL [Intersil Corporation]

General Operating Information
I
The I
input. It can accept positive current from a resistor
connected to a positive voltage source or the positive
supply. The instantaneous bias for the multiplier gain core is
proportional to this current value. Negative applied current
will put the multiplier portion of the circuit in a zero bias state
and the voltage at the pin will be clamped at a diode drop
below ground. The part will respond in a similar manner to
currents from a current source such as the output of a
transconductance amplifier or one of its own outputs. The
overall transfer equation for the EL4083 is:
K(I
As can be seen from the equation, the Z input can serve as a
divisor input. However, it is different from the other two
inputs in that the value of its current determines the supply
current of the part and the bandwidth and compliance range
of the outputs and other two inputs. Table 1 gives the
equations describing these and other important
relationships. These dependencies can complicate and/or
limit the usefulness of this pin as a computational input. The
I
Z
Z
Positive Supply Current
Negative Supply Current
Power Dissipation (See Figures 4 and 5)
Multiplying Input(s) Impedance
Multiplying Input(s) Clip Point
Multiplying Input(s) Full Scale Value
Multiplying Input Resistor Values
(In Terms of Peak Input Signal)
Full Scale Output (Single Ended)
Full Scale Output (Differential)
I
I
I
I
Z
Z
X
X
dependence of the impedance of the multiplying inputs
, I
, I
Input (Bias, Divisor) and Power Supplies
X
(Bias) Input Voltage vs I
Signal Bandwidth vs I
Y
Y
× I
Z
Signal Bandwidth vs I
1% Settling Time vs I
pin is a low impedance (< 20Ω) virtual ground current
Y
)/I
Z
= (I
XY
-IXY), K ~ 1
Z
Z
Z
Z
7
TABLE 1. BASIC DESIGN EQUATIONS AND RELATIONSHIPS
EL4083
I
I
PWR = (+V
R
I
I
R
R
I
(I
(See Figure 10)
(See Figure 11)
(See Figure 6)
(See Figure 7)
S
S
X
X
XY
XY
ZX
X
Y
+ = 3.4mA + I
- = 4.5mA + I
(clip) = I
(fs) = I
= V
= V
= I
can be particularly troublesome. See the I
RMS#2 circuit sections of the application note for some
ways of dealing with this.
The primary intended use for the Z input is as a
programming pin similar in function to those on
programmable op amps. This enables one to trade off power
consumption against bandwidth and settling time and allow
the part to function within its power dissipation rating over its
full operational supply range (±4.5V - ±16.5V). The E4083
has been designed to function well for I
of 200µA < I
bandwidths of about 50MHz to over 200MHz. Higher values
of I
lower values down to zero will progressively degrade the
input referred D.C. offsets and reduce speed. Below about
50µA of bias current the internal servo amplifier loop which
maintains the I
voltage at the pin will start to move negative (see Figure 10).
This is accompanied by a significant increase in input
impedance of the pin. Figure 11 shows the A.C. bandwidth
of the I
and 7 show the bandwidth and 1% settling time of the
multiplying inputs, I
- I
= R
XY
XY
X
Y
Z
ZY
Y
(peak)/I
(peak)/I
) = I
may cause problems at temperature extremes while
= I
Y
(fs)= I
S
= (32Ω) × 1.6mA/I
Z
X
(clip) = I
- (-V
X
input as a function of the D.C. value of I
(fs) × I
Z
(fs) × I
Z
X
Y
× 27
Z
× 26
Z
S
(fs)
(fs)
× 1.25 (nominal)
)) × (4mA + I
< 1.6mA which corresponds to I
Z
Z
Y
Y
× 2
pin at ground will lose regulation and the
(fs)/(I
(fs)/I
X
and I
Z
Z
×2)
Z
Z
Y
× 26.5)
, as functions of I
Z
values in the range
Z
divider and the
Z
X
.
and I
Z
. Figures 6
Y
signal