High-efficiency power amplifier design

High-efficiency power amplifier design

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High efficiency of the power amplifier can be obtained by using Class-F and Class-E operation modes or their different approximations, depending on the technical requirements. In all cases, an efficiency improvement in practical implementation is achieved by providing the nonlinear operation conditions when an active device can operate in pinch-off and saturation regions during most of the period, resulting in the nonsinusoidal collector current and voltage waveforms, symmetrical for Class-F and asymmetrical for Class-E operation modes. In Class-F power amplifiers analyzed in frequency domain, the fundamental-frequency and harmonic load impedances are optimized by short-circuit termination and open-circuit peaking to control the voltage and current waveforms at the device output to obtain maximum efficiency. In Class-E power amplifiers analyzed in time domain, an efficiency improvement is achieved by realizing the on/off active device switching operation (saturation and pinch-off regions) with special current and voltage waveforms so that high voltage and high current do not concur at the same time.

Chapter Contents:

  • 1.1 Class-F circuit design
  • 1.1.1 Idealized Class-F mode
  • 1.1.2 Class F with maximally flat waveforms
  • 1.1.3 Class F with quarterwave transmission line
  • 1.1.4 Effect of saturation resistance
  • 1.1.5 Load networks with lumped and distributed parameters
  • 1.1.6 Design examples of Class-F power amplifiers
  • 1.2 Inverse Class F
  • 1.2.1 Idealized inverse Class-F mode
  • 1.2.2 Inverse Class F with quarterwave transmission line
  • 1.2.3 Load networks with lumped and distributed parameters
  • 1.2.4 Design example of inverse Class-F power amplifier
  • 1.3 Class E with shunt capacitance and series filter
  • 1.3.1 Optimum load-network parameters
  • 1.3.2 Effect of saturation resistance, finite switching time, and nonlinear shunt capacitance
  • 1.3.3 Load network with transmission lines
  • 1.3.4 Practical Class-E power amplifiers
  • 1.4 Class E with finite dc-feed inductance
  • 1.4.1 General analysis and optimum load-network parameters
  • 1.4.2 Parallel-circuit Class E
  • 1.4.3 Even-harmonic Class E
  • 1.4.4 Load networks with transmission lines
  • 1.5 Class E with shunt capacitance and shunt filter
  • 1.5.1 Basic analysis and optimum load-network parameters
  • 1.5.2 Load network with transmission lines
  • 1.5.3 Design example of transmission-line Class-E power amplifier
  • 1.6 Biharmonic Class-EM power amplifier
  • 1.7 High-efficiency broadband power amplifiers
  • 1.7.1 Broadband Class E with shunt capacitance
  • 1.7.2 Broadband parallel-circuit Class E
  • 1.7.3 High-efficiency mixed-mode broadband power amplifier
  • References

Inspec keywords: frequency-domain analysis; power amplifiers; electric current control; voltage control

Other keywords: class-F power amplifiers; nonlinear operation conditions; nonsinusoidal collector current; class-E operation modes; frequency domain; open-circuit peaking; short-circuit termination; high-efficiency power amplifier design; current waveform control; voltage waveform control; fundamental frequency; class-F operation modes; harmonic load impedances; active device switching operation

Subjects: Amplifiers; Current control; Mathematical analysis; Voltage control; Mathematical analysis

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