9
FN2477.7
April 25, 2013
HA-2556. Some other possible multi-operator functions are
Of course the HA-2556 is also well suited to standard
multiplier applications such as Automatic Gain Control and
Voltage 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.
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 0V to 5V.
Wave Shaping Circuits
Wave shaping or curve fitting is another class of application
for the analog multiplier. For example, where a nonlinear
sensor requires corrective curve fitting to improve linearity
the HA-2556 can provide nonintegral powers in the range of
1 to 2 or nonintegral roots in the range of 0.5 to 1.0 (refer to
FIGURE 13. PERCENTAGE DEVIATION
FIGURE 14. DIFFERENCE DIVIDED BY SUM S (For A + B
≥ 0V)
HA-2556
1/5V
X
Y
Z
VX+
VX-
VY+
VY-
VZ+
VZ-
∑
W = 5(A2-B2)
A
B
5k
+
-
+
-
A
+
-
+
-
FIGURE 12. DIFFERENCE OF SQUARES
HA-2556
1/5V
X
Y
VOUT
Z
VX+
VX-
VY+
VY-
VZ+
VZ-
∑
W = 100
B
A
A - B
A
95k
5k
R2
R1
R1 and R2 set scale to 1V/%, other scale factors possible.
For A
≥ 0V.
+
-
+
-
A
+
-
+
-
HA-2556
1/5V
X
Y
VOUT
Z
VX+
VX-
VY+
VY-
VZ+
VZ-
∑
W = 10
B
A
A - B
B + A
5k
+
-
+
-
A
+
-
+
-
FIGURE 15. AUTOMATIC GAIN CONTROL
NC
VY+
V-
VOUT
V+
NC
50
Ω
HA-2556
5k
Ω
10k
Ω
HA-5127
0.01
μF
10k
Ω
0.1
μF
1N914
5.6V
0.1
μF
+15V
20k
Ω
NC
+
-
14
15
16
9
13
12
11
10
1
2
3
4
5
7
6
8
Σ
+ -
REF
Y
X
Z
HA-2556