REF01

Rev. H | Page 10 of 12

PRECISION CURRENT SOURCE

A current source with 25 V output compliance and excellent

output impedance can be obtained using this circuit. REF01

keeps the line voltage and power dissipation constant in the

device; the only important error consideration at room

temperature is the negative supply rejection of the op amp.

The typical 3 µV/V PSRR of the OP02E creates an 8 ppm

change (3 µV/V × 25 V/10 V) in output current over a 25 V

range. For example, a 10 mA current source can be built

(R = 1 kΩ) with 300 MΩ output impedance.

mA

10

10

8

V

25

6

×

×

=

−

O

R

GND

REF01

GND

REF01

OP02E

C

C

R

2

2

2

6

6

7

3

4

6

4

4

+50V

–5V

10V

R

R

(TRIM FOR

CALIBRATION)

TO 25V

1

2

Figure 20. Precision Current Source

SUPPLY BYPASSING

For best results, it is recommended that the power supply pin be

bypassed with a 0.1 µF disc ceramic capacitor.

REFERENCE STACK WITH EXCELLENT LINE

REGULATION

Three REF01s can be stacked to yield 10 V, 20 V, and 30 V

outputs. An additional advantage is near-perfect line regulation

of the 10.0 V and 20.0 V output. A 32 V to 60 V input change

produces an output change that is less than the noise voltage of

In general, any number of REF01s can be stacked this way.

For example, 10 devices will yield outputs of 10 V, 20 V,

30 V . . . 100 V. The line voltage can change from 105 V to

130 V. However, care must be taken to ensure that the total

load currents do not exceed the maximum usable current

(typically 21 mA).

GND

REF01

GND

REF01

GND

REF01

TRIM

TRIM

10k

Ω

10k

Ω

6.8k

Ω

10k

Ω

2

6

5

4

2

6

5

4

2

6

5

4

30V

20V

10V

TRIM

32V TO 60V

TRIMMED

OUTPUTS

Figure 21. Reference Stack