Find Q Factor of Resonant Amplifier Circuit

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Discussion Overview

The discussion focuses on determining the Q factor of a resonant amplifier circuit, specifically addressing the challenges posed by the absence of a collector resistor and the implications for calculating the Q factor using standard formulas.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how to find the Q factor since the resistance "R" is not present, indicating that standard formulas like Q=(ωL/r) or Q=(Dynamic R/ωL) cannot be applied.
  • Another participant notes that the resonant tank is driven by a transistor current source, which has some output impedance "R."
  • A subsequent post seeks clarification on what the value of "R" is and how to determine it.
  • Another participant suggests that the only output resistance available is from the transistor's collector to emitter junction, estimating it to be around 50 K, but notes that this value can depend on the specific transistor used.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the value of "R" and its role in calculating the Q factor. There is no consensus on how to proceed with the calculation given the circuit's configuration.

Contextual Notes

Limitations include the lack of a clear definition for "R" in this context and the dependence on the specific transistor characteristics, which may affect the output resistance.

aspsrilanka
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How find Q factor of this resonant amp cct.because "R" is not theare,
cant apply " Q=( ωL/r) or =(Dynamic R/ωL) "
 

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The resonant tank is driven by a transistor current source which has some output impedance R
 
what said:
The resonant tank is driven by a transistor current source which has some output impedance R

Please tell me what is the R. how find that value?
 
Since there is no collector resistor, the only output resistance comes from the transistor's collector to emitter junction. It depends on the transistor you use, but generally is about 50 K.
 

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