My LF 1 kW class E PA i using a single IRFP360 at > 96 % efficiency (at
Z=R=50 Ohm of course). The driver is a ICL7667. The supply voltage is 80
VDC. That's not a dream ;-)
Stefan/DK7FC
Am 13.01.2011 18:44, schrieb mal hamilton:
Jim
What you say is correct but it is virtually impossible to achieve the 90%
plus efficiency claimed by some. The FET required in practice is not
available and these high efficiencies are only theoritical.
I have found this in practice ie 80% if you are lucky on a good day
mal/g3kev
----- Original Message -----
From: "James Moritz"<[email protected]>
To:<[email protected]>
Sent: Thursday, January 13, 2011 5:31 PM
Subject: LF: Re: FET RDS
Dear Mal, Andy, LF Group,
There is a trade-off in construction of MOSFETs - basically, for a given
area of silicon, higher BVdss requires a thicker active region of the
MOSFET with higher on resistance. You can reduce Rdson by using a greater
chip area, but that means higher capacitances, increased cost, etc. So you
can't have your cake and eat it.
In Andy's breadboard circuit, there is a mismatch between the available
MOSFET type and the available PSU voltage - the 500V BVdss is a bit too
high
for a 60V DC supply - the peak voltage in an ideal class E is 3.56 x Vdc,
perhaps you would allow 5 x Vdc for safety. 300V BVdss mosfets seem a bit
thin on the ground, so more efficient schemes might be to increase Vdc to
about 100V, or reduce it to about 40V and use lower Rdson 200V mosfets.
Cheers, Jim Moritz
73 de M0BMU
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