EMRFD Message Archive 5382

Message Date From Subject
5382 2010-10-16 13:55:49 Tim Another better-than-IRF510 contender: STP16NF06L
Having written about my fun with the IXTU12N06T a few weeks ago... this afternoon the MOSFET subject on the bench is the STP16NF06L.

This is a traditional TO-220 package and thus much easier to heat-sink than the solder-back IXTU12N06T. Rated 16 Amps, 0.09ohm, 60Volts.

I got a small push-pull setup on the bench putting out about 40W class-E on 10.1MHz into a dummy load. The gate driver has evolved in the past few weeks: now I take 10.1MHz in at about +10dBM from the VFO, run it through a diode doubler with LC peaked at 20.2MHz, into a J310's gate and then driving a 74AC74 flip-flop. The 74AC74 then drives the two phases into 4-each 74AC240 output buffers that then drives the gate.

The logic chips are run from 6V.

The cool thing with the STP16NF06L (note the "L") is that it is a logic-level gate and thus there's no level conversion from the 74AC240 output to the gate - it's directly coupled.

The Schmitt trigger drive I was using before would show some instabilities at higher output levels (> 25W) but I do not see these instabilities with the doubler-to-flip-flop approach.

The gate capacitance of the STP16NF06L is specced to be not as low as the puny IXTU12N06T but it seems to do fine nonetheless.

I was a little worried about the lack of "dead time" with pure 180 degree gate drive but my best guess, is that the class-E waveform helps shut down the gate drive in a timely fashion.

Pics at http://www.trailing-edge.com/~shoppa/STP16NF06L.html

The scope trace is the drain waveform. Note the back porch (I think this is what I want to see in class E....?), and still some ringing (I think in the scope probe).

I have a bifiliar ferrite toroid for the drain feed choke and 4xFT37-43 beads for the output transformer. No longer any DC flowing in the output transformer. Still the output magnetics (4xFT37-43 beads) is being extremely strained at the 40W level... gonna step up to a real binocular transformer soon.

Tim N3QE