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Theory of Operation

R

R

R

R

2R

2R

2R

2R

DB0

(LSB)

DB9

DB10

DB11

(MSB)

I

1

OUT

R

FB

V

REF

I

2

OUT

R

V

OUT

CODE

4096

(1)

OPA277

DAC7811

15V

V+

V

-

-

15V

GND

I

1

OUT

R

FB

V

REF

V

DD

V

DD

V

OUT

I

2

OUT

DAC7811

SBAS337C – APRIL 2005 – REVISED JULY 2007

The DAC7811 is a single channel, current output, 12-bit digital-to-analog converter (DAC). The architecture,

illustrated in Figure 25, is an R-2R ladder configuration with the three MSBs segmented. Each 2R leg of the

potential by the use of an external I/V converter op amp. The R-2R ladder is connected to an external reference

impedance to the external reference of 10k

Ω ±20%. The external reference voltage can vary over a range of

Figure 25. Equivalent R-2R DAC Circuit

Equation 1:

will also change. Because of this, the external I/V converter op amp must have a sufficiently low offset voltage

with large offset voltages can produce INL errors in the transfer function of the DAC7811 due to offset

modulation versus DAC code.

For best linearity performance of the DAC7811, a low offset voltage op amp (such as the OPA277) is

Figure 26. Voltage Output Configuration

10

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