Peak gain and IP3 of a common-emitter amplifier

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Discussion Overview

The discussion revolves around calculating the peak gain of a common-emitter amplifier, including the small signal equivalent and the implications of various components in the circuit. Participants explore theoretical aspects and practical calculations related to the amplifier's performance.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant asks how to calculate the peak gain after deriving the small signal gain formula, expressing uncertainty about the next steps.
  • Another participant suggests consulting a basic electronics book for guidance on the topic, emphasizing the importance of foundational knowledge in technical courses.
  • A participant questions the notation used for the equivalent resistance, asking for clarification on the expected dimensions and referencing the concept of resonance.
  • A different participant clarifies the resistance notation and provides a formula for the peak gain, indicating that it occurs at a specific frequency related to the inductor and capacitor values.
  • One participant confirms that the calculated result for the peak gain appears correct for the given case.

Areas of Agreement / Disagreement

The discussion includes multiple viewpoints on how to approach the problem, with some participants providing suggestions and others offering calculations. There is no clear consensus on the best method to calculate the peak gain, and uncertainty remains regarding the initial steps and notations used.

Contextual Notes

Participants express various assumptions about the circuit components and their interactions, and there are unresolved questions about the definitions and implications of certain terms, such as resonance.

DavidEE
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1. Homework Statement
Bildschirmfoto 2015-07-31 um 13.49.12.png

Homework Equations


Hi all.
Lets start with subquestion a).
How do i calculate the PEAK gain?

The Attempt at a Solution


I drew the small signal equivalent and calculated the gain: Av=vo/vi=-gm(ro//R=1kΩ//L//C)
Is that correct? How do i now calculate the peak gain?

Thank you for you help!
 

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DavidEE said:
1. Homework Statement

Homework Equations


Hi all.
Lets start with subquestion a).
How do i calculate the PEAK gain?

The Attempt at a Solution


I drew the small signal equivalent and calculated the gain: Av=vo/vi=-gm(ro//R=1kΩ//L//C)
Is that correct? How do i now calculate the peak gain?

Thank you for you help!
It seems like the best bet would be to look in a basic electronics book. Like for example your course book. You kinda like read the thing, follow through some of the worked examples. Sometimes you get stuck and you have to reread a section a few times or check something on the internet. You are wasting your own time if you really believe you can get through a technical course without reading anything. It would be better to enter the workforce straight away if you can't/won't do the basics. Flip the burgers or read the books. 18+ you're an adult. Mom and pop can't buy you a great job.
 
Wow, that was helpful, thanks!
 
David - do you really mean R||L||C ? Which dimension do you expect as a result?
Have you heard already about the term "resonance"?
 
I mean R||sL||1/sC.
r0 can be neglected.
That would result in jwRL/(R-w^2RCL+jwL).
The peak gain would be at w=1/sqrt(LC)? (Thanks LvW)
After some calculations i get Av=-gmR=-(Ic/Vt)R= -38.4, IAvI=31.7dB
 
Yes - the result looks OK (for case a).
 

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