8.2.2 Bipolar Analog Output Configuration

Programmable logic circuits (PLCs) have analog output modules that typically output ±10 V. This bipolar analog

output circuit converts the unipolar DAC output to a bipolar ±10-V output. The key performance parameters

of these circuits are noise and slew rate. The circuit can also be used to force voltage in semiconductor test

applications. Figure 8-4 shows the example configuration using the DAC82001.

DAC82001

VREF

VDD

+

–

8.25 k

33.2 k

11 k

100 pF

VREF

VOUT

VOP

15 V

–15 V

OPA210

Figure 8-4. Bipolar Analog Output Circuit

8.2.2.1 Design Requirements

• DAC output range: 0 V to 2.5 V

• PLC analog output range: –10 V to +10 V

• Noise: < 3 µV/√Hz

• Slew rate: > 1 V/µs

8.2.2.2 Detailed Design Procedure

The OPA210 output buffer provides a balance between fast settling, bandwidth, voltage and current noise, and

wide voltage rails. The buffer uses ±15-V voltage rails to make sure there is no voltage clipping. The REF5025

is a low-noise, very low-drift, precise voltage reference and is used to generate a stable 2.5-V reference for this

application. To further reduce noise, use a 100-pF capacitor between the non-inverting input pin and the output

of the OPA210.

8.2.2.3 Application Curves

Figure 8-5 shows the noise on the buffer output vs frequency using a 100-Hz to 1-MHz frequency sweep with a

grounded reference to isolate the noise in the circuit.

Frequency (Hz)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

100

1k

10k

100k

1M

Figure 8-5. Noise vs Frequency

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DAC82001

SBASAK3A – SEPTEMBER 2022 – REVISED NOVEMBER 2022

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