AD7304 datasheet(17/20 Pages) AD

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AD7304/AD7305

Rev. C | Page 17 of 20

APPLICATIONS

The AD7304/AD7305 are inherently 2-quadrant multiplying

DACs. That is, they can easily be set up for unipolar output

operation. The full-scale output polarity is the same as the

reference input voltage polarity.

In some applications, it may be necessary to generate the full

4-quadrant multiplying capability or a bipolar output swing.

This is easily accomplished using an external true rail-to-rail op

amp, such as the OP295. Connecting the external amplifier with

two equal value resistors, as shown in Figure 38, results in a full

4-quadrant multiplying circuit. In this circuit, the amplifier

provides a gain of two, which increases the output span

magnitude to 10 V. The transfer equation of this circuit shows

that both negative and positive output voltages are created as

the input data (D) is incremented from code zero (VOUT = –5 V)

to midscale (VOUT = 0 V) to full scale (VOUT = +5 V).

REF

OUT

−

128

(2)

+5V

10k

Ω

10k

Ω

AD7304

REF

–5V

< V

OUT < +5V

2.2pF

Figure 38. 4-Quadrant Multiplying Application Circuit

AD7304 Datasheet(PDF) 17 Page - Analog Devices