HA2556 Datasheet, PDF (17/20 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.
Well, OK a multiplier can’t do nonintegral roots “exactly” but
we can get very close. We can approximate nonintegral
roots with equations of the form:
Vo = ( 1 – α) VI2N + αVIN
Vo = ( 1 – α) VI1N^{⁄ 2} + αVIN
Figure 18 compares the function V_OUT = V_IN0.7 to the
approximation V_OUT = 0.5V_IN0.5 + 0.5V_IN.
1
0.8
X^0.7
HA-2556
1
REF
NC 2
16 NC
15 NC
NC 3
14 NC
+
V_IN
NC 4
+
13
X
5
Y
- ¹²
6_-
11 +V
+
1-α
-V 7
+
Σ
-
Z
10
α
8
-⁹
0.6
0.5X^0.5+ 0.5X
0.4
0.2
X
0
0
0.2
0.4
0.6
0.8
1
INPUT (V)
FIGURE 18. COMPARE APPROXIMATION TO NONINTEGRAL
ROOT
This function can be easily built using an HA-2556 and a
potentiometer for easy adjustment as shown in Figures 19
and 20. If a fixed nonintegral power is desired, the circuit
shown in Figure 21 eliminates the need for the output buffer
amp. These circuits approximate the function _VIMN where M
is the desired nonintegral power or root.
HA-2556
1
REF
NC ₂
16 NC
15 NC
NC 3
NC 4
+
5
Y
6_-
-V 7
8
14 NC
+
13
X
- ¹²
11 +V
+
+
Σ
-
Z
10
-⁹
V_IN
1-α
α
1.0 ≤ M ≤ 2.0
0V ≤ V_IN ≤ 1V
-
+
HA-5127
V_OUT
FIGURE 20. NONINTEGRAL POWERS - ADJUSTABLE
V_OUT
HA-2556
1
REF
NC 2
16 ^NC
15 NC
NC 3
14 NC
+
V_IN
NC 4
13
+
X
5
Y
- ¹²
6_-
11 +V
R1
+
-V 7
+
Σ
-
Z
10
8
-⁹
R2
1.2 ≤ M ≤ 2.0
R3
R4
0V ≤ V_IN ≤ 1V
VOUT
=
-¹⁵


R_----3
R4
+
1_
VI2N
+


R_----3
R4
+
1_


------^R----²------
R1 + R2


VIN
Setting:
1–α
=
15_-


R_----3
R4
+
1_
α
=


R_----3
R4
+
1




------^R----²------
R1 + R2


FIGURE 21. NONINTEGRAL POWERS - FIXED
0.5 ≤ M ≤ 1.0
0V ≤ V_IN ≤ 1V
-
+
HA-5127
V_OUT
FIGURE 19. NONINTEGRAL ROOTS - ADJUSTABLE
8-23
Spec Number 511063-883