Development and Characterization of a Precise Current Source of Low Noise and High Stability

A current source with high stability and low noise is required in multiple applications. This paper develops a Voltage-Controlled Current Source (VCCS) that achieves bipolar outputs by a voltage follower using a cascaded positive-negative-positive (PNP) transistor, a Negative-Positive-Negative (NPN) transistor, and a voltage feedback. This configuration enables a current output range up to 1 A with a resolution of 0.1 mA. We performed experiments to characterize the current source and found that it has a small current ripple. Its noise is about 5.9 μA/Hz^1/2 at 1 A, 50 Hz that outperforms commercial current sources. A twenty-hour measurement shows that the statistical uncertainty of the current is about 5.3 ppm.