ha1-2557/883 Intersil Corporation, ha1-2557/883 Datasheet - Page 10

• Manufacturer Part Number: ha1-2557/883
• Description: Wideband Four Quadrant Analog Multiplier Current Output
• Manufacturer: Intersil Corporation

DESIGN INFORMATION
The information contained in this section has been developed through characterization by Intersil Semiconductor and is for use as
application and design information only. No guarantee is implied.
Applications Information
Operation at Reduced Supply Voltages
The HA-2557 will operate over a range of supply voltages,
input and output voltage ranges. See “Typical Performance
Curves” for more information.
Offset Adjustment
The channel offset voltage may be nulled by using a 20K poten-
tiometer between the V
necting the wiper to V-. Reducing the channel offset voltage will
reduce AC feedthrough and improve the multiplication error.
Theory of Operation
The HA-2557 creates an output current that is the product of
the X and Y input voltages divided by a constant scale factor
of 10kV . The resulting output has the correct polarity in
each of the four quadrants defined by the combinations of
positive and negative X and Y inputs. This results in the fol-
lowing equation, where X and Y are high impedance differ-
ential inputs:
To accomplish this the differential input voltages are first
converted into differential currents by the X and Y input
transconductance stages. The currents are then scaled by a
constant reference and combined in the multiplier core. The
multiplier core is a basic Gilbert Cell that produces a differ-
ential output current proportional to the product of X and Y
input signal currents. This current is converted into the out-
put for the HA-2557.
The purpose of the reference circuit is to provide a stable
current, used in setting the scale factor. This is achieved with
a bandgap reference circuit to produce a temperature stable
voltage of 1.2V which is forced across a NiCr resistor. Slight
adjustments to scale factor may be possible by overriding
the internal reference with the V
used to maintain the output of the multiplier within the nor-
mal operating range of 1.6mA when full scale inputs are
applied.
Communications
The multiplier function of the HA-2557 has applications in
AM Signal Generation, Synchronous AM Detection and
Phase Detection. These circuit configurations are shown in
Figure 2, Figure 3 and Figure 4. By feeding a signal into both
X and Y inputs a Square function results that is useful as a
Frequency Doubler as shown in Figure 5. The HA-2557 is
particularly useful in applications that require the interaction
of high speed signals. Both inputs X and Y have similar wide
bandwidth and input characteristics. This is unlike earlier
5V to 15V. Use of supply voltages below 12V will reduce
I
YIO
OUT
or V
=
XIO
------------ -
10kV
X x Y
REF
adjust pin A and B and con-
pin. The scale factor is
(Continued)
HA2557
8-21
products where one input was dedicated to a slow moving
control function as is required for Automatic Gain Control.
The HA-2557 is versatile enough for both.
ACOS(
ACOS(
AM SIGNAL
I
CARRIER
OUT
CARRIER
I
CCOS(
AUDIO
ACOS(
OUT
FIGURE 3. SYNCHRONOUS AM DETECTION
DC COMPONENT IS PROPORTIONAL TO COS( )
)
=
LIKE THE FREQUENCY DOUBLER YOU GET
AUDIO CENTERED AT DC AND 2F
)
FIGURE 2. AM SIGNAL GENERATION
=
-------------- -
20kV
C
FIGURE 4. PHASE DETECTION
AC
-------------- -
20kV
)
)
A 2
V
V
Y
1/10kV
1/10kV
V
V
V
V
V
V
+
X
Y
X
X
Y
X
Y
1/10KV
V
+
Cos
V
V
V
+
+
-
-
-
-
X
Y
X
Y
Cos
+
+
-
+
-
-
+
-
+
+
-
-
+
+
-
-
C
–
+
Y
X
X
Y
Spec Number
A
Cos 2
X
Y
X
X
X
+
Cos
R
C
Z
.
R
+
R
Z
Z
C
+
511064-883
I
A
OUT
I
OUT
I
OUT