AD538
Rev.
E
| Page
13
of
16
ANALOG C
OMPUTATION
OF P
OWERS
A
ND
R
OOTS
It is often necessary to raise the quotient of two input signals to
a power or take a root. This could be squaring, cubing, square
rooting or exponentiation to some noninteger power. Examples
include power series generation. With the AD538, only one or
two
external resistors are required to set
any
desired power, over
the range of 0.2 to 5. Raising the basic quantity V
Z
/V
X
to a
power greater than one requires that the gain of the AD538’s log
ratio subtractor be increased, via an external resistor between
th
e
A and D
pins
. Similarly, a voltage divider that attenuates the
log ratio output between
Point
B and
Point
C will program the
power to a value less than one.