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High Precision, Low Cost Current Sources Using the AD8276 Difference Amplifier and the AD8603 Op Amp (CN0099)
Figure 2: Test Results for Current Source Using the AD8276A, AD8603, and 2N3904 (R1 = 50 Ω, RLOAD = 100 Ω, Vs = +5 V, TA = 25°C)
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| Figure 2: Test Results for Current Source Using the AD8276A, AD8603, and 2N3904 (R1 = 50 Ω, RLOAD = 100 Ω, Vs = +5 V, TA = 25°C) |
As with any high accuracy circuit, proper layout, grounding, and decoupling techniques must be employed. See Tutorial MT-031, Grounding Data Converters and Solving the Mystery of AGND and DGND and Tutorial MT-101, Decoupling Techniques for more details.
Common VariationsIf higher power supplies are needed for higher value output current, the OP1177, AD8661, and AD8663 can be used. The important specifications are power supply range, bias current, offset voltage, input voltage range, and temperature drift.
If a fixed current source is required, VREF can be supplied by a voltage reference such as the ADR36x family.
The ADR82x family integrates a voltage reference and an op amp and can operate on a power supply up to 36 V. This provides an additional space saving option.
If a dual-current source is needed, the AD8607 and the are good choices.
If programmable current sources are needed, use a precision 14-bit or 16-bit DAC to generate the reference voltage, VREF. The AD5560, AD5060 (single), and AD5663R (dual) are suitable for this application.
，高精度，低成本电流源使用AD8276差分放大器和AD8603