"Murray" bravely wrote to "All" (26 Apr 05 19:29:08)
--- on the heady topic of " Replace 6CW4?"

Mu From: Murray
Mu Xref: aeinews rec.radio.amateur.homebrew:9477

Mu It should be remembered that FETs are a voltage controlled
Mu current device. A tube is a voltage controlled voltage device.
Mu A bipolar transistor is a current controlled current device.

Mu A FET is therefore somewhere in between a tube and a transistor.

If we look at the characteristic I/V plate curves for a pentode it is
easy to see a similarity with the collector saturation plots of a
transistor. The FET in my opinion is different from the pentode
analogy but it is a little more like the triode.

The combination of bipolar transistor and FET is called a BiFET and
this is perhaps most like a pentode than anything. There is also power
HEXFETs which are something amazing with extremely low ON resistances
in the milli-ohm range. These might be more like a triode on steroids.
These come in pretty high voltage versions which seem to me more
suitable to replace a 6CW4 with some bias voltage adjusting of course.

A*s*i*m*o*v

.... "If it ain't broke, you're not tryin!" - Red Green