10

®

DAC701, 702, 703

APPLICATIONS

DRIVING AN EXTERNAL OP AMP

WITH CURRENT OUTPUT D/AS

DAC702 is current output devices and will drive the sum-

ming junction of an op amp to produce an output voltage as

shown in Figure 9. Use of the internal feedback resistor is

required to obtain specified gain accuracy and low gain drift.

DAC702 can be scaled for any desired voltage range with an

external feedback resistor, but at the expense of increased

drifts of up to

±50ppm/°C. The resistors in the DAC702 ratio

track to

±1ppm/°C but their absolute TCR may be as high as

±50ppm/°C.

An alternative method of scaling the output voltage of the

D/A converter and preserving the low gain drift is shown in

Figure 10.

OUTPUTS LARGER THAN 20V RANGE

For output voltage ranges larger than

±10V, a high voltage

op amp may be employed with an external feedback resistor.

Use I

–2mA for unipolar voltage ranges (see Figure 11). Use

protection diodes as shown when a high voltage op amp is

used.

Common

I

OUT

V

OUT

R

F

5k

Ω

4k

Ω

0 to

2mA

FIGURE 9. External Op Amp Using Internal Feedback

Resistors.

I

OUT

V

OUT

R

F

5k

Ω

4k

Ω

0 to

2mA

R

1

I

*

R

Common

R

1

*, R

FIGURE 10. External Op Amp Using Internal and External

Feedback Resistors to Maintain Low Gain Drift.

FIGURE 11. External Op Amp Using External Feedback

Resistors.

V

OUT

R

F

4k

Ω

0 to

2mA

BB3584

R

F