45. JFET Common Drain Amplifier
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- Опубликовано: 25 дек 2016
- The Common Drain, or Source Follower, is the second of three JFET amplifier configurations we look at. The device has slightly less than unity gain but tremendous current increases and a very high input impedance. As always, the circuit is analyzed theoretically/ mathematically and a sample circuit is tested to confirm expectations.
This is a slightly revised video of an earlier version on the same topic. I didn't like the AC analysis so I modified it a little. 
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can you explain to me in detail the graph you used in this video to find the desired Igs current and Vgs voltage? What do x coordinate and y coordinate represents and how do you find the exact point where the Igs and Vgs values are?
Really like your videos! Please consider doing a video about negative feedback, distortion, etc.
Jörgen Overgaard Hello again. I haven't forgotten. I'll try to do one soon.
Looking forward to it! Thanks! :D
Thank you for your video, it's very interesting and useful. But it's not very strict as in my opinion ;)
Can you explain 14:18 why we need to find so Vgs = Vg - Vrs. But we can get this value directly from the graph.
I have done some experiments - I've got exact (as it possible) graph Id(Vgs) for a particular transistor samples and then calculate common drain amplifier like you did. And Vgs from the graph much closer to reality.
@ 1:53, did you mean an order of magnitude smaller, for the gate to source resistance, in which case would be considered negligible?
Hello, The gate to source resistance is many times greater than the value of RG (tera-ohms in some cases) so the current that flows from g to s is negligible compared to the current through RG itself. Hope that helps and thanks for watching.
how about p type jfet?
yep