ADR280

–4–

ADR280

–5–

The ADR280 provides the core 1.2 V band gap voltage and is

able to drive a maximum load of only 100 µA. Users can simply

buffer the output for high current or sink/source current applica-

tions, such as ADC or LCD driver references (see Figure 5).

V+

0.1F

0.1F

V–

ADR280

U1

U2

U2 = AD8541, SC70

AD8601, SOT-23-5

Figure 5. Buffered Output

Users can also tailor any specific need for voltage and dynamics

with an external op amp and discrete components (see Figure 5).

Depending on the specific op amp and PCB layout, it may be

necessary to add a compensation capacitor, C2, to prevent gain

peaking and oscillation.The exact value of C2 needed requires

some trial and error but usually falls in the range of a few pF.

V+

0.1F

V–

ADR280

U1

5V

5V

1.2V

U2

1.8V

R1

R2

60k 0.1%

120k 0.1%

C2

2.2pF

V+

V–

AD8541

C1

Figure 6. 1.8 V Reference

LOW COST, LOW POWER CURRENT SOURCE

Because of its low power characteristics, the ADR280 can be

converted to a current source with just a setting resistor. In addi-

tion to the ADR280 current capability, the supply voltage and the

load limit the maximum current.The circuit in Figure 7 produces

100 µA with 2 V compliance at 5 V supply. The load current is

V+

0.1F

V–

ADR280

U1

5V

1.2V

13.6k

C1

100A

+

–

Figure 7. Low Cost Current Source

Precision Low Power Current Source

V+

0.1F

V–

ADR280

U1

5V

C2

RL 1k

100A

V+

V–

5V

U2

12k

AD8541

Figure 8. Precision Low Power Current Source

Boosted Current Source

Adding one more buffer to the previous circuit boosts the current

to the level that is limited only by the buffer U2 current handling

capability (see Figure 9).

V+

0.1F

V–

ADR280

U1

5V

C1

230

RL

500

5mA

V+

V–

5V

U3

V+

V–

5V

U2

U2 = U3 = AD8542, AD822

1.2V

+

–

Figure 9. Precision Current Source

REV. A

REV. A