Datasheet

ADR5040/ADR5041/ADR5043/ADR5044/ADR5045 Data Sheet
Rev. B | Page 12 of 16
Adjustable Precision Voltage Source
The ADR5040/ADR5041/ADR5043/ADR5044/ADR5045,
combined with a precision low input bias op amp such as the
AD8610, can be used to output a precise adjustable voltage.
Figure 22 illustrates the implementation of this application
using the ADR5040/ADR5041/ADR5043/ADR5044/ADR5045.
The output of the op amp, V
OUT
, is determined by the gain of the
circuit, which is completely dependent on the resistors, R1 and R2.
V
OUT
= (1 + R2/R1)V
REF
An additional capacitor, C1, in parallel with R2, can be added to
filter out high frequency noise. The value of C1 is dependent on
the value of R2.
AD8610
R
BIAS
V
REF
GND
R1
R2
C1
(OPTIONAL)
V
OUT
= V
REF
(1 + R2/R1)
ADR5040/ADR5041/
ADR5043/ADR5044/
ADR5045
V
CC
06526-022
Figure 22. Adjustable Voltage Source
Programmable Current Source
By using just a few ultrasmall and inexpensive parts, it is possible
to build a programmable current source, as shown in Figure 23.
The constant voltage on the gate of the transistor sets the current
through the load. Varying the voltage on the gate changes the
current. The AD5247 is a digital potentiometer with I
2
C® digital
interface, and the AD8601 is a precision rail-to-rail input op
amp. Each incremental step of the digital potentiometer increases
or decreases the voltage at the noninverting input of the op amp.
Therefore, this voltage varies with respect to the reference
voltage.
I
LOAD
AD8601
V+
V–
AD5247
ADR5040/
ADR5041/
ADR5043/
ADR5044/
ADR5045
R
SENSE
R
BIAS
06526-023
V
DD
Figure 23. Programmable Current Source