HA2556 Datasheet, PDF (16/20 Pages) Intersil Corporation – Wideband Four Quadrant Analog Multiplier (Voltage Output)

HA2556
DESIGN INFORMATION (Continued)
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.
Other Applications
As shown above, a function may contain several different
operators at the same time and use only one HA-2556.
Some other possible multi-operator functions are shown in
Figure 12, Figure 13 and Figure 14.
Of course the HA-2556 is also well suited to standard multi-
plier applications such as Automatic Gain Control and Volt-
age Controlled Amplifier.
Automatic Gain Control
Figure 15 shows the HA-2556 configured in an Automatic
Gain Control or AGC application. The HA-5127 low noise
amplifier provides the gain control signal to the X input. This
control signal sets the peak output voltage of the multiplier to
match the preset reference level. The feedback network
around the HA-5127 provides a response time adjustment.
High frequency changes in the peak are rejected as noise or
the desired signal to be transmitted. These signals do not
indicate a change in the average peak value and therefore
no gain adjustment is needed. Lower frequency changes in
the peak value are given a gain of -1 for feedback to the
control input. At DC the circuit is an integrator automatically
compensating for Offset and other constant error terms.
This multiplier has the advantage over other AGC circuits, in
that the signal bandwidth is not affected by the control signal
gain adjustment.
HA-2556
1
NC ²
NC ³
NC ⁴
V_Y+ ⁵
6
-V ⁷
8
REF
X
Y
+
Σ
-
Z
16 _NC
15 _NC
14 _NC
13
12
11 _+V
10
9
50Ω
10kΩ
0.1µF
V_OUT
1N914
5kΩ
10kΩ
+15V
20kΩ
0.01µF
-
+
HA-5127
5.6V
0.1µF
HA-2556
1
NC 2
NC 3
NC 4
5
6
-V 7
8
REF
X
Y
+
Σ
-
Z
16 NC
15 NC
14 NC
13 V_X+ (V_GAIN)
12
11 + V
10
9
V_OUT
5kΩ
500Ω
-
V_IN
+
HFA0002
FIGURE 16. VOLTAGE CONTROLLED AMPLIFIER
Voltage Controlled Amplifier
A wide range of gain adjustment is available with the Voltage
Controlled Amplifier configuration shown in Figure 16. Here
the gain of the HFA0002 can be swept from 20V/V to a gain
of almost 1000V/V with a DC voltage from 0 to 5V.
Wave Shaping Circuits
Wave shaping or curve fitting is another class of application
for the analog multiplier. For example, where a non-linear
sensor requires corrective curve fitting to improve linearity
the HA-2556 can provide nonintegral powers in the range 1
to 2 or nonintegral roots in the range 0.5 to 1.0 (refer to Fur-
ther Reading). This effect is displayed in Figure 17.
1
0.8
X^0.5
0.6
X^0.7
0.4
X^1.5
0.2
X²
0
0
0.2
0.4
0.6
0.8
1
INPUT (V)
FIGURE 17. EFFECT OF NONINTEGRAL POWERS / ROOTS
FIGURE 15. AUTOMATIC GAIN CONTROL
8-22
Spec Number 511063-883