REF02

Rev. I | Page 12 of 16

PRECISION CURRENT SOURCE

A current source with 35 V output compliance and excellent

output impedance can be obtained using this circuit. REF02

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 a 20 ppm change

(3 µV/V × 35 V/5 V) in output current over a 25 V range. For

example, a 5 mA current source can be built (R = 1 kΩ) with

350 MΩ output impedance.

GND

REF02

GND

REF02

OP02E

C

C

R

2

2

2

6

6

7

3

4

6

4

4

+50V

–5V

5V

R

35V

20

R

(TRIM FOR

CALIBRATION)

TO 25V

1

2

Figure 22. Precision Current Source

GND

TRIM

REF02

2

6

5

4

R

TEMP

3

15V

5V

R

+ 1mA

VOLTAGE COMPLIANCE: –25V TO +8V

Figure 23. 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.

GND

TRIM

REF02

2

6

5

4

R

TEMP

3

–15V

5V

R

+ 1mA

VOLTAGE COMPLIANCE: –9V TO +25V

Figure 24. Current Sink

REF02

DAC08

OP02

0.1

µF

+15V

4

6

5

5k

Ω

5k

Ω

5k

Ω

5k

Ω

+15V

–15V

–15V

+15V

LSB

MSB

2

B1 B2 B3 B4 B5 B6 B7 B8

V+

V–

2

4

O

GND

Figure 25. DAC Reference

GND

REF02HJ

2

6

4

A1

–7.5V

+7.5V

A2

–7.5V

1/2 OP04CK

1/2 OP04CK

–7.5V (

±10%)

+7.5V (

±10%)

R3

1k

Ω

R1

20k

Ω

R2

13.3k

Ω

R4

2k

Ω

Figure 26. ±3 V Reference