1Amp constant current source for milliohm meter

2 layer board of 2.36x2.17 inches (60.02x55.02 mm).
Shared on August 11th, 2015 23:13.

1Amp constant current source. You can use this constant current source to measure very low resistances since the voltage drop is R=V/I i.e. 1mV over each 1mΩ.

To guarantee correct operation and not thermally overstress IC1, U1 and R5 keep input voltage between 6.5V≥Vin≥9V

Calibrate with P1 to achieve exactly 1Amp at output with short circuit load or 1V with 1Ω resistor load.

BOM: IC1 LM317T; U1 LT3083; R1 1K6; R2 3K9; R3 18K; R4 910R; R5 1R 0.1% 1W; R6 130R; P1 5K 10turn precision poti; C1 10µF/5V tantal; C2 15pF ceramic; C3 10µF/5V tantal; LED1 green; heatsink of maximum 3K/W or lower for IC1, U1 and R5;

For schematics look here: https://www.dropbox.com/s/cs31b9lijhswvi1/1Amp%20constant%20current%20source.pdf?dl=0

For thermal calculation look here: https://www.dropbox.com/s/gdbk54ipaouoct8/1Amp%20current%20source%20thermal%20calculations.pdf?dl=0

Have fun!

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