HA2556 Datasheet, PDF (15/20 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.
Current Output
Another useful circuit for low voltage applications allows the
user to convert the voltage output of the HA2556 to an out-
put current. The HA-2557 is a current output version offering
100MHz of bandwidth, but its scale factor is fixed and does
not have an output amplifier for additional scaling. Fortu-
nately the circuit in Figure 10 provides an output current that
can be scaled with the value of R_CONVERT and provides an
output impedance of typically 1MΩ. The equation for I_OUT
becomes:
IOUT = -^A----^×₅-----^B- × _R----_C---_O----_N--¹--_V---_E---_R----_T-
A
V_X +
+
-
V_X -
1/5V
B
V_Y +
+
-
V_Y -
HA-2556
X
+
∑
-
Y
Z
V_OUT
A
R_CONVERT
V_Z +
+
-
V_Z -
I_OUT
FIGURE 10. CURRENT OUTPUT
CH A
CH B
NC
NC
NC
V_Y +
V_Y -
-15V
1
REF
2
16
NC
15
NC
3
4
5
+_-
6
7
8
14
NC
+
-
13
V_X +
V_MIX
(0V to 5V)
12
11
+
Σ
-
+^-
10
9
+15V
V_Z -
V_Z +
V_OUT
A
5K
B
5K
50Ω
FIGURE 11. VIDEO FADER
V_X +
+
-
V_X -
1/5V
V_Y +
+
-
V_Y -
HA-2556
X
+
∑
-
Y
Z
W = 5(A²-B²)
A
5K
V_Z +
+
-
V_Z -
5K
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 11 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.
The Balance equation looks like:
( VMIX) × ( ChA – ChB) = 5 ( VOUT – ChB)
Which simplifies to:
VOUT = ChB + -^V---^M-₅---^I-^X-- ( ChA – ChB)
When V_MIX is 0V the equation becomes V_OUT = Ch B and
Ch A is removed, conversely when VMIX is 5V the equation
becomes V_OUT = Ch A eliminating Ch B. For VMIX values 0V
≤ VMIX ≤ 5V the output is a blend of Ch A and Ch B.
FIGURE 12. DIFFERENCE OF SQUARES
R1
5K
A
95K R2 HA-2556
V_X -
+
V_X +
-_X
1/5V
+
∑
V_Y +
+Y
-
-
Z
V_Y -
A-B
V_OUT W = 100 _A
A
V_Z +
+
B
-
V_Z -
R1 and R2 set scale to 1V/%, other scale factors possible
for A ≥ 0V.
FIGURE 13. PERCENTAGE DEVIATION
V_X -
+
-
V_X +
HA-2556
X
V_OUT
A
A-B
W = 10 _{B + A}
1/5V
+
∑
V_Y +
+
Y
-
Z
V_Z +
+
B
-
-
A
5K
V_Y -
V_Z -
5K
FIGURE 14. DIFFERENCE DIVIDED BY SUM (FOR A + B ≥ 0V)
Spec Number 511063-883
8-21