CAT5121 CATALYST [Catalyst Semiconductor], CAT5121 Datasheet - Page 8

• Manufacturer Part Number: CAT5121
• Description: 16-Tap MiniPot Digitally Programmable Potentiometers with 2-Wire Interface
• Manufacturer: CATALYST [Catalyst Semiconductor]

The Minipots are intended for circuits requiring digitally
controlled adjustable resistance, such as LCD contrast
control, where voltage biasing adjusts the display con-
trast.
Use an op amp to provide buffering and gain on the
output of the CAT5120. Connect the mechanical
potentiometer to the positive input of a noninverting op
amp (Figure 3) to select a portion of the input signal by
digitally controlling the wiper terminal. Figure 4 shows a
similar circuit for the CAT5121.
Doc. No. 2121, Rev. A
CAT5120
+5V
L
H
W
V
IN
H
L
CAT5121
V
CC
30V
V
OUT
V
OUT
8
Figure 5 shows how to use the variable resistor to
digitally adjust the gain of a noninverting op amp
configuration. Connect the CAT5121 in series with a
resistor to ground to form the adjustable gain control of
a noninverting amplifier. The Minipots have a low 5ppm/
˚C ratiometric tempco that allows for a very stable
adjustable gain configuration over temperature.
CAT5121
L
V
IN
+5V
W
CAT5120
H
L
H
V
CC
30V
V
OUT
V
OUT