On Fri, 18 Mar 2005 09:45:02 -0800, Roy Lewallen
wrote:

A major problem with the speed is that a common three-terminal
Darlington doesn't have any pulldown resistor or current sink to the
Q1e-Q2b connection. That leaves no good way to remove charge from Q2b
quickly when you want Q2 to turn off. If you can find one with an
internal Q2b-Q2e resistor of pretty low value, or better yet have access
to that junction so you can long-tail it down to a negative supply or
even to ground, you'll have a much faster switching device. I still
suspect you'll have trouble getting one to go fast enough for efficient
class C operation at VHF.

Roy Lewallen, W7EL


perhaps not so much for RF, but I wonder why you don't see NPN/PNP
combination for darlington transistors - with Vbe = 0.55-0.6V

Jan-Martin, LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm