
7
current through this resistor reaches 1.2mA, all the current
available is flowing in the one side and full scale has been
reached. Normally the 1.67k
internal resistor sets the scale
factor to 2V when the Gain Adjust pins B and C are connected
together, but you may set this resistor to any convenient value
using pins 16 (GA A) and 15 (GA C) (See Figure 3).
Typical Applications
Automatic Gain Control
In Figure 4 the HA-2546 is con
figure
d in a true Automatic
Gain Control or AGC application. The HA-5127, low noise op
amp, provides the gain control level to the X input. This level
will set the peak output voltage of the multiplier to match the
reference level. The feedback network around the HA-5127
provides stability and a response time adjustment for the
gain control circuit.
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 5. Here
the gain of the HFA0002 is swept from 20V/V at a control
voltage of 0.902V to a gain of almost 1000V/V with a control
voltage of 0.03V.
Video Fader
The Video Fader circuit provides a unique function. Here Ch B
is applied to the minus Z input in addition to the minus Y input.
In this way, the function in Figure 6 is generated. V
MIX
will
control the percentage of Ch A and Ch B that are mixed
together to produce a resulting video image or other signal.
Many other applications are possible including division,
squaring, square-root, percentage calculations, etc. Please
refer to the HA-2556 four quadrant multiplier data sheet for
additional applications.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
REF
NC
NC
V
Y
+
V-
V
OUT
V+
V
X
+
NC
X
Z
Y
Σ
+
-
+
-
+
-
+
-
NC
1K
MULTIPLIER, V
OUT
= V
X
V
Y
/ 2V
SCALE FACTOR = 2V
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
REF
NC
NC
V
Y
V-
V
OUT
V+
V
X
+
NC
X
Z
Y
Σ
+
-
+
-
+
-
+
-
NC
1K
MULTIPLIER, V
OUT
= V
X
V
Y
/ 5V
SCALE FACTOR = 5V
4.167K
FIGURE 3. SETTING THE SCALE FACTOR
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
REF
NC
NC
V
Y
+
V-
V
OUT
V+
NC
X
Z
Y
Σ
+
-
+
-
+
-
+
-
NC
50
5k
10k
-
+
HA-5127
0.01
μ
F
10k
0.1
μ
F
1N914
3.3V
0.1
μ
F
+15V
20k
FIGURE 4. AUTOMATIC GAIN CONTROL
HA-2546