ABSTRACT
The accepted method to design high-power radio frequency (RF) amplifier is using the large-signal input and output impedances provided by the manufacturer for RF transistors. The input drive signal for push–pull amplifiers is out phased by 180° using transformers such as input balun. RF power output in amplifier system can be increased by also paralleling the transistors. RF output power can be increased further up to several kWs by combining individual identical power amplifier (PA) modules. This chapter discusses the amplifier classes such as Class A, Class B, and Class AB for linear mode of operation. For amplifier Classes A, B, and C, transistor can be modeled as the voltage-dependent current source. Classes A, B, and AB amplifiers are considered to be linear amplifiers, where the phase and amplitude of output signal are linearly related to amplitude and phase of input signal. The chapter illustrates the efficiency distribution and power capacity of conventional amplifier Classes A, B, AB, and C.
