Patent ID: 6317002
Filing Date: 2001-11-13
Classification: H03F

Abstract:
A multiple power level low power radio frequency amplifier comprising:a first transistor for amplifying a radio frequency signal at substantially a peak efficiency, said transistor having a collector circuit connected to a first impedance matching network, and a base circuit connected to receive said radio frequency signal;a second transistor for amplifying said radio frequency signal at substantially a peak efficiency, said second transistor having a collector circuit connected to a second impedance matching network, and a base circuit connected to receive said radio frequency signal;an output impedance matching network connected to said first and second impedance matching networks, and to an load impedance;a base control circuit for selectively enabling one or both of said transistor base circuits to amplify said radio frequency signal at a peak efficiency, whereby one or more of said transistors is enabled to amplify said radio frequency signal; anda decoupling element connected between said first and second impedance matching networks, wherein said transistors are decoupled when one of said transistors is amplifying said signal, so that each amplifying transistor has a collector which sees substantially the same impedance whether one or more transistors are enabled to amplify said radio frequency signal.