REV. B

OP290

–9–

1/2

OP290GP

1

1/2

OP290GP

3

2

7

5

6

R1

250k

C1

0.1 F

+15V

–15V

R2

100k

R3

1M

D2

D1

DIODES ARE 1N4148

4

R4

25k

C1

4700pF

8

Figure 6. Variable Slew Rate Filter

LOW OVERHEAD VOLTAGE REFERENCE

Figure 7 shows a voltage reference that requires only 0.1 V of

overhead voltage. As shown, the reference provides a stable

4.5 V output with a 4.6 V to 36 V supply. Output voltage drift is

only 12 ppm/

°C. Line regulation of the reference is under 5 µV/V

with load regulation better than 10

µV/mA with up to 50 mA of

output current.

The REF-43 provides a stable 2.5 V which is multiplied by the

OP290. The PNP output transistor enables the output voltage

to approach the supply voltage.

Resistors R1 and R2 determine the output voltage.

VV

R

R

OUT

=+









25

1

2

1

.

The 200

Ω variable resistor is used to trim the output voltage.

For the lowest temperature drift, parallel resistors can be used in

place of the variable resistor and taken out of the circuit as required

to adjust the output voltage.

6

2

4

REF-43FZ

R1B

200

20-TURN

BOURNS 3006P-1-201

GND

R1A

2.37

1%

C1

10 F

C2

0.1 F

V+

R2

2k

1%

2N2907A

1

1/2

OP290GP

3

2

8

4

Figure 7. Low Overhead Voltage Reference