#374

This video discusses the JFET current source / limiter circuits, illustrating the very simple circuit structure, its operation, and the pros and cons of these circuits. The background videos that may be helpful to review would be:
Intro to FETs:
   • #219: Back to Basics: Introduction to...  
Transistor (BJT) Current Sources and Mirrors:
   • #190: Back to Basics: Transistor Curr...  
   • #191: Beware of test equipment loadin...  
The notes from this video can be found here:
http://www.qsl.net/w2aew/youtube/JFET...
BONUS! 50uA Current Source, like the one to calibrate Simpson 260 VOM, built using a single JFET and the cascode design, traced out on the curve tracer, including a zoom in to 1uA/div:
http://www.qsl.net/w2aew/youtube/50uA...
The Siliconix AppNote on JFET current sources:
https://www.vishay.com/docs/70596/705...