Amplifier Circuit and Method

An amplifier arrangement, comprising:

• N amplifier stages coupled to an output impedance network, the output impedance network comprising a cascade of quarter wavelength transmission lines;
• a main amplifier and a plurality of peaking amplifiers configured to operate in a Doherty mode of operation;
• wherein the amplifier arrangement is configured such that at least two peaking amplifiers are collectively driven by time-delayed versions of the same signal;
• and
• at least one of the following is true:
• at least one of the quarter wavelength transmission lines of the cascade is extended by a half wavelength transmission line or multiples of half wavelength transmission lines;
• at least one of the peaking amplifiers is coupled to a respective junction or output node of the cascade via a connecting half wavelength transmission line or multiples of half wavelength transmission lines.

A method of improving the efficiency of an amplifier arrangement comprising N amplifier stages coupled to an output impedance network, the impedance network comprising a cascade of quarter wavelength transmission lines, wherein the amplifier arrangement comprises a main amplifier and a plurality of peaking amplifiers configured to operate in a Doherty mode of operation, the method comprising:

• collectively driving at least two peaking amplifiers by time-delayed versions of the same signal;
• at least one of:
• extending at least one of the quarter wavelength transmission lines in the cascade by a half wavelength transmission line or multiples of half wavelength transmission lines;
• coupling at least one of the peaking amplifiers to its respective junction or an output node via a connecting half wavelength transmission line or multiples of half wavelength transmission lines.