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Date: Thu, 13 Jan 2011 22:36:31 +0100
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: Re: Re: FET RDS
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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"<james.moritz@btopenworld.com>
> To:<rsgb_lf_group@blacksheep.org>
> 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
>>
>>
>>
>>      
>