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.

8-23

HA2556

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:

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 V

IN

M

where M

is the desired nonintegral power or root.

FIGURE 19. NONINTEGRAL ROOTS - ADJUSTABLE

V

o

1

α

–

IN

2

αV

IN

+

=

V

o

1

α

–

IN

12

⁄

αV

IN

+

=

0

0.2

0.4

0.6

0.8

1

0

0.2

0.4

0.6

0.8

1

INPUT (V)

X

NC

NC

-V

+V

NC

NC

HA-2556

HA-5127

NC

NC

0V

≤ V

0.5

≤ M ≤ 1.0

α

1-

α

+

-

14

15

16

9

13

12

11

10

1

2

3

4

5

7

6

8

Σ

REF

Y

X

Z

+

-

+

-

+

-

FIGURE 20. NONINTEGRAL POWERS - ADJUSTABLE

FIGURE 21. NONINTEGRAL POWERS - FIXED

NC

NC

-V

+V

NC

NC

HA-2556

HA-5127

NC

NC

0V

≤ V

1.0

≤ M ≤ 2.0

α

1-

α

+

-

14

15

16

9

13

12

11

10

1

2

3

4

5

7

6

8

Σ

REF

Y

X

Z

+

-

+

-

+

-

NC

NC

-V

+V

NC

NC

HA-2556

NC

NC

0V

≤ V

1.2

≤ M ≤ 2.0

R3

R4

R1

R2

V

OUT

1

5

--

R3

R4

-----

1

+





V

IN

2

R3

R4

-----

1

+





R2

R1

R2

+

-----------------





V

IN

+

=

1

α

–

1

5

--

R3

R4

-----

1

+





=

α

R3

R4

-----

1

+





R2

R1

R2

+

-----------------





=

Setting:

14

15

16

9

13

12

11

10

1

2

3

4

5

7

6

8

Σ

REF

Y

X

Z

+

-

+

-

+

-

Spec Number

511063-883