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AS1504, AS1505

Data Sheet

Increasing Output Voltage Swing

Figure 20. Output Buffering

Increasing Output Voltage Swing

An external amplifier can be used to extend the output voltage swing beyond the power supply rails of the AS1504/

AS1505. This design allows for a simple digital interface to the DAC, while expanding the output swing to take advan-

tage of higher voltage external power supplies (e.g., DAC 1 of Figure 21 is configured to swing from -5 to +5V). The

actual output voltage is given by:

(EQ 3)

Where:

D is the DAC input value (i.e., 0 to 255).

This design can be combined with the circuit in Figure 20 if very accurate adjustments around 0V are required.

Figure 21. Increasing Output Voltage Swing

resistors can be adjusted to provide scaling of the output voltage, within the limits of the external operational amplifier

power supplies.

–

+

AS1504/

AS1505

GND

Amplifier

–

+

100k

Ω

Simple Buffer

0 to 5V

Summer Circuit with

Fine Trim Adjustment

+5V

DAC1

DAC2

DAC3

DAC1

OUT1

DAC2

AS1504/

AS1505

GND

AS1505

Only

OUT2

–

+

100k

Ω

100k

Ω

0 to +10V

–

+

100k

Ω

-5 to +4.98V

100k

Ω

+5V

-5V

+12V

+5V