[Amps] Class E amd and MRF492

[G3rzp@aol.com]

In a message dated 09/03/2005 14:14:18 GMT Standard Time, wlfuqu00 at uky.edu  
writes:

The  polar loop system is a variation of the DAF amplifier. 


I think that there's a fundamental difference between the DAF and  polar 
loop. The major one is that polar loop has a negative feedback mechanism,  while 
the DAF runs open loop.
 
Now if you modulated the supply volts to the Class E amplifier in sympathy  
with the envelope so that it was always hard switching, you should be able to  
keep the efficiency up. It would give an interesting problem in doing a  
suitable switching modulator - by rule of thumb, I'd expect it to need a  bandwidth 
of around 30kHz and a switching frequency in the hundreds of kHz,  which 
would be interesting EMC wise, too. Anything else and you'll lose  efiiceincy.
 
Perhaps a better approach might be to use two Class E stages in a  Callum 
modulator
 
73
 
Peter G3RZP