250mA high-precision dc-current source for joule balance at NIM

For application in the magnetic field of joule balance at NIM, a dc-current source with 250mA for magnetic system, based on series compensation type, has been developed. Through designing the extraordinary sampling resistor, selecting stable voltage reference and operational amplifier with outstanding properties, the stability of this customized constant current source approached to 4.5×10
^-6
/30min, which at present was satisfied with the requirement of magnetic system.