REF01/REF02/REF03

Rev. K | 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.

REF03

GND

V+

V–

2

3

4

6

7

2

U1

U2

4

6

OP97

100k

Ω

–2.5V

+2.5V

100k

Ω

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 REF0x 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.

REF03

GND

V+

V+

2

3

4

6

7

+15V

50k

Ω

2

U1

U2

4

6

OP97

50k

Ω

50k

Ω

–2.5V TO +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 −2.5V 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.