Design Goals
DAC Supply Voltage | Amplifier Supply Voltage | DAC Voltage | Output Voltage | Error |
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5V | ±15V | 0V–2.5V | ±10V | <0.25% FSR |
Design Description
The unipolar to bipolar output voltage circuit converts the voltage from a unipolar DAC into a bipolar voltage span. The circuit consists of a DAC, op amp, voltage reference, and three resistors to set the scale and span of the bipolar output voltage. This circuit is commonly used in Analog output module, Field Transmitters, and other applications requiring a programmable bipolar voltage.
Design Notes
- Choose a DAC with low gain error, offset error, drift, and INL. Use a high-voltage op amp with low offset voltage and low offset voltage drift.
- Use precision 0.1% or better tolerance resistors with low temperature drift.
- Use a DAC with integrated reference to minimize solution size.
Design Steps
1. The voltage output based on DAC voltage, reference voltage, and resistors is given by:
2. Set the DAC voltage to zero to calculate ratio of RFB and RG1 to create the desired negative full-scale output. Select standard resistor values to produce this gain.
3. Calculate RG2 based on the full-scale range required, in this case 20V to produce ±10V range.
4. The output error can be approximated based on DAC TUE, amplifier offset voltage, resistor tolerance, and reference initial accuracy using root sum square (RSS) analysis.
DC Transfer Characteristic
Small Signal Step Response
Devices
Device | Key Features | Link | Other Possible Devices |
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DACs |
DAC8560 | 16-bit resolution, single channel, internal reference, low power, 4 LSB INL, SPI, 2V to 5.5V supply | 16-bit, single-channel, low-power, ultra-low glitch, voltage output DAC with 2.5V, 2ppm/°C reference | Precision DACs (≤10 MSPS) |
DAC80501 | 16-bit resolution, 1LSB INL, Single-Channel, Voltage Output DAC with 5ppm Internal Reference | True 16-bit, 1-ch, SPI/I2C, voltage-output DAC in WSON package with precision internal reference | Precision DACs (≤10 MSPS) |
DAC8830 | 16-bit resolution, single channel, ultra-low power, unbuffered output, 1 LSB INL, SPI, 2.7V to 5.5V supply | 16-bit, single-channel, ultra-low power, voltage output DAC | Precision DACs (≤10 MSPS) |
Amplifiers |
OPA188 | Low-Noise, Low Offset Voltage, RRO, Zero-Drift, ±2V to ±18V supply | Precision, Low-Noise, Rail-to-Rail Output, 36V Zero-Drift Operational Amplifier | Operational amplifiers (op amps) |
OPA196 | Low-Power, Low Offset Voltage, RRIO, ±2V to ±18V supply | One-channel, 1MHz, rail-to-rail input and output 1.8V to 5.5V operational amplifier | Operational amplifiers (op amps) |
TLV170 | Cost Sensitive, Rail-to-Rail Output, ±1.35V to ±18V supply | Low Offset, Rail-to-Rail I/O Operational Amplifier | Operational amplifiers (op amps) |