100 w amplifier operating class

265 views

Skip to first unread message

Tom Thompson W0IVJ

unread,

Aug 12, 2020, 9:52:26 AM8/12/20

to RFPowerTools Forum

Hi Jim---I really enjoyed your Virtual Hamvention presentation. From the spectrum analyzer plots, I assume the 100 w amplifier is linear and operating in class A since it is a single transistor. How does a 100 ma quiescent current put the transistor in class A when the power supply current is 4 amps? What am I missing here?

WA2EUJ

unread,

Aug 12, 2020, 10:18:02 AM8/12/20

to RFPowerTools Forum

I wasn't particularly worried about the operating class of the amplifier. The datasheet for the MRF-101 makes it look very linear at 13.56MHz with IDQ of 100mA up to 100W:

My circuit adds negative feedback that further linearizes the amp. With IMD products between -38 dB and -41dB I'd say that it's better than you can get with a Class AB. Maybe if the bias was increased, the linearity would improve even further but I haven't made any measurements at increased bias levels.