Common Source MOSFET Amp problem

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SUMMARY

The discussion centers on analyzing a common source MOSFET amplifier with specific parameters: μnCox = 400 μA/V², W/L = 10, VA = 10V, and a bias current ID = 0.2mA using a drain resistor RD = 6kΩ. Key calculations involve determining the input resistance (Rin), voltage gain (AVO), and output resistance (RO) using the equations AVO = -gm(RD||ro) and RO = RD||r0. The user successfully identifies that the bias current provides critical information for calculating transconductance (gm) and output resistance (ro).

PREREQUISITES
  • Understanding of MOSFET parameters, including μnCox and W/L ratios.
  • Familiarity with hybrid-pi model for small-signal analysis.
  • Knowledge of basic amplifier design equations, particularly for common source configurations.
  • Ability to calculate equivalent resistances in parallel circuits.
NEXT STEPS
  • Calculate transconductance (gm) using the formula gm = 2ID/VA.
  • Explore the concept of output resistance (ro) in MOSFET amplifiers.
  • Study the impact of biasing on amplifier performance and stability.
  • Learn about the significance of the small-signal model in amplifier design.
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in MOSFET amplifier analysis and design.

vermin
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Homework Statement



A CS amplifier utilizes a MOSFET with μnCox = 400 μA/V2, W/L = 10, and VA=10v. It is biased at ID=0.2mA and uses RD=6k.

Find Rin,AVO,RO

Homework Equations



VAO= -gm(RD||ro)

Ro=RD||r0

The Attempt at a Solution



I drew out the equivalent circuit with hybrid-pi model. Doesn't seem to tell me much.

Not sure where to start. For the relevant equations above I'm missing gm and ro. I have a feeling "it is biased at ID=0.2mA" is a clue but I'm having trouble finding what that implies.
 
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ok nevermind I just figured it out.
 
Last edited:

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