June 23, 2013
June 23, 2013
June 26, 2013
Division Experimentation & Lab-Oriented Studies
23.1326.1 - 23.1326.11
Using Miller’s Theorem and Dominant Poles to Accurately Determine Field EffectTransistor and Bipolar Junction Transistor Small Signal and SPICE Capacitor ValuesErnest M. Kim, P.E. and Thomas F. Schubert, Jr., P.E.AbstractThe most accurate method for determining high frequency cutoff for Bipolar Junction Transistor(BJT) and Field Effect Transistor (FET) small signal amplifiers is to use Miller’s Theorem tosimplify frequency response analysis in junior and senior level Electrical Engineering electroniccircuits courses. Dominant pole analysis can be used to simplify analysis can be used to furthersimplify calculations of the high frequency cutoff. Unfortunately, accurate small signalcapacitance values are difficult to determine. Using manufacturer’s SPICE data can yield largeerrors when comparing simulation, analysis and experimental data.By using dominant pole analysis under two different input resistance conditions yields, for thesame amplifier, a dominant pole due to low input resistance and another for a high inputresistance corresponding with the pole associated with the output small signal equivalent circuitof the transistor amplifier and the pole associated with the input small signal equivalent circuitrespectively.By experimentally determining the two cutoff frequencies (dominant poles) from the two inputresistance conditions using essentially the identical amplifier, and using expressions for the twopoles of the small signal amplifier model, accurate small signal capacitance values aredetermined. These values are mathematically converted to SPICE equivalent transistor modelcapacitances using established SPICE relationships. The resulting simulation corresponds wellwith experimental data and analytical calculations.Assessments of the student results and confidence in applying the dominant pole calculations todetermining transistor model capacitances and in designing other active circuits using thismethod will be presented. Faculty assessment of student results and confidence, as measured byscoring short answers to knowledge statements, will be presented.
Kim, E. M., & Schubert, T. F. (2013, June), Using Miller’s Theorem and Dominant Poles to Accurately Determine Field Effect Transistor and Bipolar Junction Transistor Small Signal and SPICE Capacitor Values Paper presented at 2013 ASEE Annual Conference & Exposition, Atlanta, Georgia. https://peer.asee.org/22711
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