DAC0832 datasheet(14/28 Pages) NSC

Part #	DAC0832

Description	8-Bit P Compatible, Double-Buffered D to A Converters

PDF	28 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

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14 / 28 page

DAC0830 Series Application Hints

(Continued)

2.5 Zero Adjustment

For accurate conversions, the input offset voltage of the

output amplifier must always be nulled. Amplifier offset errors

create an overall degradation of DAC linearity.

The fundamental purpose of zeroing is to make the voltage

appearing at the DAC outputs as near 0V

DC as possible.

This is accomplished for the typical DAC — op amp con-

nection (

Figure 7) by shorting out R

fb, the amplifier feedback

resistor, and adjusting the V

OS nulling potentiometer of the

op amp until the output reads zero volts. This is done, of

course, with an applied digital code of all zeros if I

OUT1 is

driving the op amp (all one’s for I

OUT2). The short around Rfb

is then removed and the converter is zero adjusted.

00560839

OP Amp

(O to Full Scale)

LF356

22 pF

4 µs

LF351

22 pF

5 µs

LF357*

10 pF

2 µs

*2.4 k

Ω RESISTOR ADDED FROM−INPUT TO GROUND TO

INSURE STABILITY

FIGURE 8.

DAC0832 Datasheet(PDF) 14 Page - National Semiconductor (TI)