Datasheet

Data Sheet REF01/REF02/REF03
Rev. M | Page 17 of 20
BIPOLAR VOLTAGE REFERENCE
Many applications require both a positive and reference voltage
of the same magnitude. A simple method of generating such a
bipolar reference is shown in Figure 42.
00375-043
REF03
V
IN
GND
V+
V–
2
3
4
6
7
2U1
U2
4
6
V
OUT
OP97
100kΩ
–2.5V
+2.5V
100kΩ
Figure 42. Bipolar Voltage Reference
In this configuration, the negative rail is generated simply
with an inverting amplifier with a gain of −1. A low offset
op amp should be used to minimize the voltage error at the
negative output.
ADJUSTABLE REFERENCE WITH POSITIVE AND
NEGATIVE SWING
The output voltage of the REF01/REF02/REF03 references can
be readily adjusted via a simple trim circuit (explained in the
Output Adjustment section). The circuit shown in Figure 43
extends the negative range of adjustment beyond that
obtainable with the simple trim circuit by employing a precision
op amp with
a potentiometer feeding the op amp’s noninverting input.
00375-044
REF03
V
IN
GND
V+
–15V
2
3
4
6
7
+15V
50kΩ
2U1
U2
4
6
V
OUT
OP97
50kΩ
50kΩ
V
OUT
–2.5V T
O +2.5V
Figure 43. Negatively Adjustable Reference
The voltage output from the op amp can be adjusted by
changing the value of the potentiometer: as shown, the op
amp outputs +2.5 V when the pot is pulled completely high,
and −2.5 V when pulled completely low. In this configuration,
the load current is sourced by the op amp; therefore, a low
offset op amp with a current rating that meets or exceeds the
current requirements of the load should be used.