X9313
Applications Information
Electronic digitally controlled potentiometers (XDCP) provide
three powerful application advantages; (1) the variability and
reliability of a solid-state potentiometer, (2) the flexibility of
computer-based digital controls, and (3) the retentivity of
nonvolatile memory used for the storage of multiple
potentiometer settings or data.
Basic Configurations of Electronic Potentiometers
V
R
V
H
V
W
/R
W
V
R
V
L
I
THREE-TERMINAL POTENTIOMETER;
VARIABLE VOLTAGE DIVIDER
TWO-TERMINAL VARIABLE RESISTOR;
VARIABLE CURRENT
Basic Circuits
BUFFERED REFERENCE VOLTAGE
R
1
+V
+5V
V
W
V
REF
–
+
–
-5V
R
1
V
OUT
= V
W
/R
W
(a)
(b)
V
O
= (1 + R
2
/ R
1
)V
S
V
W
OP-07
V
OUT
+V
V
W
/R
W
X
-5V
+V
CASCADING TECHNIQUES
+V
V
S
+
NONINVERTING AMPLIFIER
+5V
LM308A
V
O
R
2
VOLTAGE REGULATOR
OFFSET VOLTAGE ADJUSTMENT
R
1
R
2
COMPARATOR WITH HYSTERESIS
V
IN
317
R
1
V
O
(REG)
V
S
100kΩ
–
+
V
O
V
S
LT311A
–
+
V
O
}
}
I
adj
R
2
10kΩ
10kΩ
V
O
(REG) = 1.25V (1 + R
2
/ R
1
) + I
ADJ
R
2
+12V
-12V
10kΩ
TL072
R
1
R
2
V
UL
= [R
1
/ (R
1
+ R
2
)] V
O
(max)
V
LL
= [R
1
/ (R
1
+ R
2
)] V
O
(min)
(for additional circuits see AN115)
9
FN8177.2
September 9, 2005
INTERSIL [ INTERSIL CORPORATION ]
