Low Burden Voltage Current Measurement Circuit
Thought for 4 sec
I haven’t made schematic changes yet; the project is still empty with 0 components and 0 nets.
To start this SMT µCurrent-style adapter correctly, I need a few design requirements because they materially affect the topology, op-amp choice, protection, range switching, and output scaling:
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Current ranges: What current range(s) do you want to measure?
Example: pA–nA, nA–µA, µA–mA, or multiple selectable ranges. -
Target burden voltage: What maximum voltage drop across the DUT is acceptable?
Example: <1 mV, <10 mV, <100 µV. -
Output format to DMM: Should the banana output be a voltage proportional to current?
Example:1 mV/nA,1 mV/µA,1 V/µA, etc. -
DMM input mode: Will the DMM measure the adapter output in voltage mode, not current mode?
That is the usual approach for reducing burden voltage. -
Power source: Preferred power supply?
Options: coin cell, AAA/AA, 9 V battery, Li-ion/LiPo, USB-C, or external supply. -
Polarity: Do you need bidirectional current measurement, or only one current direction?
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Accuracy target: Desired accuracy/resolution?
Example: 0.1%, 1%, 10 pA resolution, etc. -
Product constraints: Any size, cost, calibration, enclosure, or banana jack preferences?
Once these are defined, the next step is to design the schematic around a low-bias-current transimpedance amplifier with protected current input, precision feedback networks/ranges, low-noise power, output protection for the DMM terminals, and calibration/test points.
Set current ranges
Set burden target
Define DMM output
Set power and polarity
Start architecture
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