A 250 mA high-precision DC current source with improved stability for the Joule Balance at NIM

In this paper, the reasons for the unsatisfactory stability of the DC current source early used for the Joule Balance at NIM are discussed. The structure and principle of the compensation circuit to improve the current stability are presented. A 250 mA DC current source with stability about 0.25 ppm in 30 minutes and more than 100 W output power is realized and tested. Measurement results show that the compensation circuit is effective and the current stability is improved more than one order of magnitude than the source early used.