Programmable, very low noise current source.

Area of Science:

• Electronics
• Instrumentation
• Metrology

Background:

• Accurate low-frequency noise measurements require highly stable and low-noise current sources.
• Existing programmable current sources often struggle with noise performance at very low frequencies.

Purpose of the Study:

• To develop a new programmable current source with very low noise for low-frequency noise measurements.
• To achieve high accuracy and stability in sourced current, particularly at sub-Hertz frequencies.

Main Methods:

• Utilizing a low-noise Junction Field Effect Transistor (JFET) as the core high-impedance current source.
• Implementing a programmable floating voltage source based on a photovoltaic MOSFET driver for current setting.
• Incorporating advanced filtering and a control network with super-capacitors to minimize low-frequency output noise.

Main Results:

• The developed system achieves output noise levels comparable to the intrinsic JFET noise down to 100 mHz.
• Current programmability is achieved using a standard Digital-to-Analog converter with accuracy better than 1%.
• A prototype demonstrated effective current sourcing from hundreds of microamperes to a few milliamperes, with RMS noise below 14 pA in the 0.1–10 Hz bandwidth.

Conclusions:

• The proposed approach effectively realizes a very low noise programmable current source suitable for demanding low-frequency noise measurement applications.
• The design demonstrates superior noise performance at very low frequencies, outperforming conventional methods.
• The system offers a practical solution for precise current control in sensitive electronic measurements.