Datasheet

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.
00375-F-021
GND
REF02
GND
REF02
OP02E
C
C
R
2
2
2
6
6
7
3
4
6
4
4
+50V
–5V
I
O
=
5V
R
R
O
=
35V
20
× 10
–6
× 5mA
R
(TRIM FOR
CALIBRATION)
V
IN
V
O
V
IN
V
O
V
O
= 0V
TO 25V
1
2
Figure 22. Precision Current Source
00375-F-022
V
IN
GND
TRIM
V
O
REF02
2
6
5
4
R
TEMP
3
15V
I
OUT
I
OUT
= +
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.
00375-F-023
V
IN
GND
TRIM
V
O
REF02
2
6
5
4
R
TEMP
3
–15V
I
OUT
I
OUT
= +
5V
R
+ 1mA
VOLTAGE COMPLIANCE: –9V TO +25V
Figure 24. Current Sink
00375-F-024
REF02
DAC08
OP02
0.1µF
+15V
4
6
5
5kΩ
5kΩ
5kΩ
5kΩ
+15V
–15V
–15V
+15V
E
O
LSB
MSB
2
B1 B2 B3 B4 B5 B6 B7 B8
V+
V–
C
C
V
LC
2
4
V
IN
V
O
GND
l
O
l
O
Figure 25. DAC Reference
00375-F-025
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
1kΩ
R1
20kΩ
R2
13.3kΩ
V
O
(–) = –3V
V
O
(+) = +3V
R4
2kΩ
V
IN
V
O
Figure 26. ±3 V Reference