ha9p2546-5 Intersil Corporation, ha9p2546-5 Datasheet - Page 6

• Manufacturer Part Number: ha9p2546-5
• Description: 30mhz, Voltage Output, Two Quadrant Analog Multiplier
• Manufacturer: Intersil Corporation

Application Information
Theory Of Operation
The HA-2546 is a two quadrant multiplier with the following
three differential inputs; the signal channel, V
the control channel, V
V
amplifier. The differential voltages of channel X and Y are
converted to differential currents. These currents are then
multiplied in a circuit similar to a Gilbert Cell multiplier,
producing a differential current product. The differential
voltage of the Z channel is converted into a differential
current which then sums with the products currents. The
differential “product/sum” currents are converted to a single-
ended current and then converted to a voltage output by a
transimpedance amplifier.
The open loop transfer equation for the HA-2546 is:
The scale factor is used to maintain the output of the
multiplier within the normal operating range of 5V. The
scale factor can be defined by the user by way of an optional
external resistor, R
Adjust A (GA A), Gain Adjust B (GA B), and Gain Adjust C
(GA C). The scale factor is determined as follows:
The scale factor can be adjusted from 2 to 5. It should be
noted that any adjustments to the scale factor will affect the
AC performance of the control channel, V
input operating range of V
voltage.
The typical multiplier configuration is shown in Figure 2. The
ideal transfer function for this configuration is:
The V
V
quadrant operation. If the V
the V
control input.
V
SF = 2, when GA B is shorted to GA C
SF
SF
V
where;
Z
X+
OUT
OUT
+ and V
is negative there is no signal at the output, i.e. two
X+
GA A and GA C (R
1.2 (R
1.2 R
connected to GA B and GA C (R
X-
= A
=
pin maybe grounded and the V
pin is usually connected to ground so that when
(V
Z
EXT
EXT
-, to complete the feedback of the output
A = Output Amplifier Open Loop Gain
SF = Scale Factor
V
X+
(V
X
, when R
, V
X+
- V
+ 1.667k ), when R
Y
, V
X-
- V
EXT
) (V
2
0
Z
X
X-
SF
, and the Gain Adjust pins, Gain
+ and V
= Differential Inputs
) (V
EXT
Y+
EXT
X
X
Y+
- V
is equal to the scale factor
is connected between
is in k )
input is a negative going signal
6
- V
Y-
X
-, and the summed channel,
)
+ V
Y-
)
- (V
EXT
Z-
EXT
, when V
, when V
X-
Z+
is
X
pin used as the
. The normal
- V
is in k )
Y
Z-
+ and V
X
)
X
< 0V
0V
Y
-,
HA-2546
The V
swing 5V. The V
V
while V
by connecting GA B to GA C. Therefore the transfer equation
simplifies to V
Offset Adjustment
The signal channel offset voltage may be nulled by using a
20k potentiometer between V
connecting the wiper to V-. Reducing the signal channel
offset will reduce V
can also be nulled by connecting V
potentiometer which is tied between V+ and V-.
Capacitive Drive Capability
When driving capacitive loads >20pF, a 50 resistor is
recommended between V
output (see Figure 2). This will prevent the multiplier from going
unstable.
Power Supply Decoupling
Power supply decoupling is essential for high frequency
circuits. A 0.01 F high quality ceramic capacitor at each
supply pin in parallel with a 1 F tantalum capacitor will
provide excellent decoupling. Chip capacitors produce the
best results due to the close spacing with which they may be
placed to the supply pins minimizing lead inductance.
Adjusting Scale Factor
Adjusting the scale factor will tailor the control signal, V
input voltage range to match your needs. Referring to the
simplified schematic on the front page and looking for the V
input stage, you will notice the unusual design. The internal
reference sets up a 1.2mA current sink for the V
pair. The control signal applied to this input will be forced
across the scale factor setting resistor and set the current
flowing in the V
OUT
Y-
to complete the feedback loop of the output amplifier
V
Z-
NC
NC
NC
Y
terminal is usually grounded allowing the V
V-
+
is grounded. The scale factor is normally set to 2
1
2
3
4
5
6
7
8
OUT
+
X+
-
Y
Z+
REF
side of the differential pair. When the
= (V
X
terminal is usually connected directly to
AC feedthrough. Output offset voltage
50
X
OUT
V
FIGURE 2.
Y
+
) / 2.
-
and V
YIO
X
Z
+
-
Z-
Z+
Adjust pins A and B and
+
-
to the wiper of a 20k
, using V
16
15
14
13
12
11
10
9
NC
V+
V
1k
X
+
Z+
X
differential
as the
Y+
50pF
V
X
OUT
to
,
X