A 2'4GHz 0'18um CMOS SelfBiased Cascode Power Amplifier

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A 2.4-GHz 0.18-um CMOS Self-Biased Cascode Power
Amplifier
IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 38,
NO. 8, AUGUST 2003
Tirdad Sowlati, Member, IEEE, and Domine M. W.
Leenaerts, Senior Member, IEEE

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Introduction (1)

• Oxide breakdown sets a limit on the maximum
  signal swing on drain.
• Hot carrier degradation is a reliability issue.
  It increases the threshold voltage and
  consequently degrades the performance of the
  device.
• Cascode configuration and thick-oxide transistors
  have been used.

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Introduction (2)

• This work demonstrates a 0.18-um CMOS self-biased
  cascode RF power amplifier that operates at 2.4
  GHz and provides 23 dBm from a 2.4-V supply
  voltage for Class-1 Bluetooth application.
• By using standard oxide thickness devices in the
  process, the design takes full advantage of the
  technology and its high Ft.

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Conventional cascode amplifier and Voltage
waveforms versus time
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Self-biased cascode amplifier and Voltage
waveforms versus time
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Bootstrapped cascode amplifier and Voltage
waveforms versus time
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Two-stage self-biased cascode PA
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Simulate output power, gain, and PAE
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Conventional and Self-biased Cascode PA
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Microphotograph of the PA
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Measured Pout , gain, and PAE versus Pin
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Pout versus time of continuous operation
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Bluetooth spectrum at the output of the PA
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SLIDING BIAS TECHNIQUE

• To improve the linearity of a PA
• Operate the PA in class A/AB mode
• Use a bias boosting or gain boosting at the
  compression point
• Employ a de-biasing technique at low and
  intermediate power levels to have the same gain
  at the maximum power

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Measured Gain and PAE versus Pout for
constant/sliding gate bias voltages
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Measured phase variations versus inputs power for
constant/sliding bias
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Conclusion

• A self-biased cascode topology was applied to
  reduce hot carrier effects.
• No performance degradation occurs after ten days
  of continuous operation under maximum output
  power conditions.
• Using a sliding biasing technique on both stages,
  improve the PAE at low/mid-power level and
  linearize the PA.