High Efficiency Power Amplifiers

30 Questions | Total Attempts: 41

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High Efficiency Power Amplifiers


Questions and Answers
  • 1. 
    The conditions for unconditional stability of a transistor are
    • A. 

      K>1, B>0 and µ>1

    • B. 

      K<1, B>0 and µ>1

    • C. 

      K>1, B>0 and µ<1

    • D. 

      None of the above

  • 2. 
    The main advantage of switched mode PA is
    • A. 

      Bandwidth improvement

    • B. 

      Linearity improvement

    • C. 

      Efficiency improvement

    • D. 

      Gain improvement

  • 3. 
    The harmonic load conditions of Class F PA are
    • A. 

      Z(2f)=0, Z(3f)=Infinity

    • B. 

      Z(2f)=0, Z(3f)=0

    • C. 

      Z(2f)= Infinity , Z(3f)= Infinity

    • D. 

      Z(2f)= Infinity , Z(3f)=0

  • 4. 
    The second harmonic load in class E/F2 mode is
    • A. 

      Short circuit

    • B. 

      Open circuit      

    • C. 

      Capacitive

    • D. 

      Inductive

  • 5. 
    In Class B power amplifier mode which of the components are short circuit
    • A. 

      Even harmonics

    • B. 

      Odd harmonics

    • C. 

      All harmonics

    • D. 

      None of the above

  • 6. 
    The small signal gain is lowest in the case of
    • A. 

      Class A

    • B. 

      Class B

    • C. 

      Class C

    • D. 

      Class AB

  • 7. 
    Among the following, the frequency component that comparatively spreads widely on smith chart is
    • A. 

      Fundamental component

    • B. 

      Second harmonic

    • C. 

      Third harmonic

    • D. 

      None

  • 8. 
    Continuous Class J PA is used to improve
    • A. 

      Bandwidth

    • B. 

      Efficiency

    • C. 

      Bandwidth and Efficiency

    • D. 

      Linearity

  • 9. 
    Which matching condition can be used for the design of PA?
    • A. 

      Load-pull

    • B. 

       Loadline

    • C. 

      Waveform Engineering 

    • D. 

      All of the above

  • 10. 
    Centre of the Smith chart represents
    • A. 

      Short

    • B. 

      Open

    • C. 

      Matched load

    • D. 

      None of the above

  • 11. 
    The theoretical maximum drain efficiency of 100% can be achieved if
    • A. 

      Power dissipation is zero

    • B. 

      Harmonic power is zero

    • C. 

      Harmonic power and power dissipation are zero

    • D. 

      Fundamental and harmonic powers are zero

  • 12. 
    In Class F power amplifier transistor operates as
    • A. 

      Switch

    • B. 

      Voltage source

    • C. 

      Current source

    • D. 

      All odd harmonics

  • 13. 
    Which of the following power amplifier mode can achieve theoretical 100% drain efficiency with minimum number of harmonics
    • A. 

      Class AB

    • B. 

      Class F

    • C. 

      Class J

    • D. 

      Class E

  • 14. 
    The transistor is operated as a switch in
    • A. 

      Class F-1

    • B. 

      Class E

    • C. 

      Class J

    • D. 

      Class F

  • 15. 
    What are the conditions to ensure the lossless operation when voltage is applied across the switch?
    • A. 

      Bias condition

    • B. 

      ZVDS

    • C. 

      ZVS

    • D. 

      ZVS and ZVDS

  • 16. 
    The load conditions of waveform engineered power amplifiers are defined at
    • A. 

      Current source reference plane

    • B. 

      Package plane

    • C. 

      Parasitic plane

    • D. 

      None of the above

  • 17. 
    The second harmonic load in continuous class B/J is
    • A. 

      Complex

    • B. 

      Purely resistive

    • C. 

      Short circuit     

    • D. 

      Purely reactive

  • 18. 
    The continuous class E/F mode operates as conventional class E mode when φ1 is
    • A. 

      43.3⁰    

    • B. 

      57.5⁰    

    • C. 

      78⁰       

    • D. 

      90⁰       

  • 19. 
    Doherty power amplifier is used to improve
    • A. 

      Output power at saturation

    • B. 

      Efficiency at saturation

    • C. 

      Efficiency at back-off

    • D. 

      Output power at back-off

  • 20. 
    LINC stands for
    • A. 

      Low-noise Amplification with Nonlinear Components

    • B. 

      Linear Amplification with Nonlinear Components

    • C. 

      Low-noise Amplification with Nominal Components

    • D. 

      Linear Amplification with Nominal Components

  • 21. 
    Which of the following is true for power amplifier working in saturation region?
    • A. 

      Efficiency is low

    • B. 

      Linearity is high

    • C. 

      Efficiency is high

    • D. 

      DC power to RF power conversion rate is low.

  • 22. 
    For a two-tone signal with frequency f1 and f2, which of the following pairs represent the second and third IMD terms respectively
    • A. 

      3f1 and 2f1+f2

    • B. 

      F1-f2 and 2f1+f2

    • C. 

      F1+f2 and 2f2

    • D. 

      2f1-f2 and 2f2

  • 23. 
    If a PA has output powers as 34 dBm, 0 dBm, and 12 dBm for output power, second-order IMD and third-order IMD components respectively by applying input signal power of 4 dBm. What will be output signal power levels for 6 dBm input signal power
    • A. 

      30 dBm, 4 dBm, and 18 dBm

    • B. 

      34 dBm, 0 dBm, 12 dBm

    • C. 

      36 dBm, 4 dBm, and 18 dBm

    • D. 

      33 dBm, 0 dBm, 12 dBm

  • 24. 
    Which of the following signals will have the highest PAPR
    • A. 

      256-QAM

    • B. 

      QPSK

    • C. 

      BPSK

    • D. 

      FM

  • 25. 
    Convert 1 W power into units of ‘dBm.’
    • A. 

      0

    • B. 

      30

    • C. 

      40

    • D. 

      10

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