Self Bias Transistor Design Problem

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SUMMARY

The forum discussion focuses on solving for the resistances RD, RS1, and RS2 in a self-bias transistor circuit. The user successfully calculated RD to be 2000 ohms using the voltage gain equation AVNL = -mg(RD//rd) with a given value of -8 for AVNL. However, the user encountered difficulties in determining RS1 and RS2, as the voltage gain is only accurately approximated as (-gm RD) when there is no un-bypassed source resistance (RS1). The discussion emphasizes the importance of understanding Vgs (quiescent) and Vds (quiescent) to derive the total source resistance and voltage gain expressions necessary for solving RS1.

PREREQUISITES
  • Understanding of self-bias transistor circuits
  • Familiarity with voltage gain equations, specifically AVNL = -mg(RD//rd)
  • Knowledge of quiescent voltages Vgs and Vds
  • Ability to derive expressions for voltage gain in transistor circuits
NEXT STEPS
  • Research methods to calculate total source resistance in transistor circuits
  • Learn how to derive voltage gain expressions for self-bias configurations
  • Study the effects of source resistance on transistor performance
  • Explore advanced transistor biasing techniques and their applications
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Electrical engineering students, circuit designers, and anyone involved in transistor circuit analysis and design will benefit from this discussion.

charkins
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Homework Statement


I have to solve for RD, RS1, and RS2.
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Homework Equations



AVNL=-mg(Rd//rd)
Vdd-Id(Rd+RStotal)=0
Bias Line Eq: Vg-Vgsq-Idq(RStotal)

The Attempt at a Solution


I have solved for RD by using the AVNL equation and the given value of -8 for AVNL.
I found RD to be 2000 ohms.

I cannot figure out how to get Rs1 and Rs2.
 
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charkins said:

The Attempt at a Solution


I have solved for RD by using the AVNL equation and the given value of -8 for AVNL.
I found RD to be 2000 ohms.

That's not correct. The voltage gain can only be approximated as (-gm Rd) if there is no un-bypassed source resistance (RS1).

Start by using the knowledge of Vgs (quiescent) to find the total source resistance (RS1+RS2), and then use the knowledge of Vds (quiescent) to find the value of RD.

Finally you need to derive (or look up) a correct expression for the voltage gain to solve for RS1.
 

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