Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Michael Koster explains it this way

" The Zout of the mu-output is a function of the gfs of the MOSFET you are using, the value of the MOSFET source resistor (Rset), and the internal plate resistance of the tube. For a "large" value source resistor the value approaches that of a simple source follower of 1/gfs and is less dependent on the tube anode resistance. For finite small Rset values, the anode current is a fraction of output current defined by 1/(gfs * Rset). The Zout thus also includes Rp / (gfs * Rset) in series.

The gfs increases, therefore Zout decreases, with increasing current. The plate resistance also decreases with increasing current, resulting also in decreased Zout at higher current. Unfortunately, higher current means a smaller value Rset, which tends to increase Zout counteracting some of the improvement due to higher gfs and lower Rp. "

"Anything you do to increase the resistance between bottom and top devices will decrease the output impedance at the "follower" output."


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"


This post is made possible by the generous support of people like you and our sponsors:
  Crux Audio  


Follow Ups Full Thread
Follow Ups

FAQ

Post a Message!

Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.