[600MRG] Class E Amplifier Performance

[Frank Lotito]

Recent posts on the 600mrg bulletin board have discussed measuring Class E Amplifier performance.  I found these posts to be excellent food for thought!  Two topics in these posts attracted my interest.  I definitely would like to know more about these topics:

(1) Inserting non-inductive resistors in the source lead of the power FET to measure the device's source current.

(2) Measuring amplifier performance where the design uses paralleled power FETs to share the load.

When I think of fractional ohm resistors, and definitely milli-ohm resistors for use as current shunts, I think of "four wire measurement" techniques.  Also coming to mind are two other related subjects: the effect of ground return impedance, which in the real world is not ideally zero, and how one determines that the current shunt and its insertion into the circuit is "non-inductive enough."

The second item attracting my interest is paralleling active devices, be it tubes as we did in the last century, or solid state devices as we presently do.  Off the cuff we used to say "use matched tubes."  I assume designers are still using that off the cuff statement.  I recall in the days of "hollow-state" amplifiers some designs used means to equalize the load when paralleled amplifying devices were used.  Some of those circuits were a little involved, but not out of the question for the casual basement experimenter using common (and affordable) test equipment.

Can someone expand on the topics of properly sampling source current in Class E amplifiers and load sharing when paralleled power FETs are used in Class E amplifiers?

73 Frank K3DZ / WH2XHA