External-Reference Stabilized Current Source with Sub-PPM Stability

The noise and stability of a commercial current source is limited by the quality of components used for construction, such as the voltage reference chips, resistors, and power supplies. A state-of-the-art commercial current source typically exhibits a stability no better than parts in 10
⁷
. In this paper, we present a way to implement a current source with “external” electrical references. This approach allows the current source stability to be decoupled from the noise characteristics of the main power supply circuit. A few parts in 10
⁸
stability is demonstrated here.