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Lecture # 5 2014 Hybrid Equivalent Shoubra/Electrical... · PDF file Lecture # 5 2014 Hybrid Equivalent Model Instructor: Dr. Ahmad El-Banna Benha University Faculty of Engineering

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Text of Lecture # 5 2014 Hybrid Equivalent Shoubra/Electrical... · PDF file Lecture # 5 2014...

  • Lecture # 5 Hybrid Equivalent Model

    Instructor: Dr. Ahmad El-Banna

    Benha University Faculty of Engineering at Shoubra

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  • Agenda

    Two-Port Systems Approach

    Cascaded Systems

    The Hybrid Equivalent Model

    Approximate & Complete h-model

    Hybrid π Model

    Troubleshooting and Practical Applications 2

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  • TWO PORT SYSTEMS APPROACH 3

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  • 2-Port System

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  • 2-Port System..

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  • CASCADED SYSTEMS 6

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  • Cascaded Systems

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    • Examples: RC Coupled ct & Cascode ct • Check Examples: 5.15 & 5.16

  • THE HYBRID EQUIVALENT MODEL 8

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  • The Hybrid Equivalent Model

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    • The re model has the advantage that the parameters are defined by the actual operating conditions,

    • the parameters of the hybrid equivalent circuit are defined in general terms for any operating conditions.

     short-circuit forward transfer current ratio parameter

    short-circuit forward transfer current ratio parameter

    open-circuit reverse transfer voltage ratio parameter

    short-circuit input-impedance parameter

  • Transistor Hybrid Equivalent ct

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    • For Transistor:

  • Hybrid vs. re model

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  • APPROXIMATE & COMPLETE H-MODEL 12

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  • Approximate h-model

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    • Fixed Bias ct

    • Check other configurations !!

  • Complete h-model

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  • HYBRID Π MODEL 15

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  • Hybrid π Model

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    It includes parameters that do not appear in the other two models primarily to provide a more accurate model for high-frequency effects.

    • The resistance rπ (using the symbol π to agree with the hybrid π terminology) is simply βre as introduced for the common-emitter re model.

    • The output resistance ro is the output resistance normally appearing across an applied load. • The resistance rb includes the base contact, base bulk, and base spreading resistance levels. • The resistance ru (the subscript u refers to the union it provides between collector and base

    terminals) is a very large resistance and provides a feedback path from output to input circuits in the equivalent model.

    • All the capacitors are stray parasitic capacitors between the various junctions of the device.

    • The controlled source can be a voltage-controlled current source (VCCS) or a current-controlled current source (CCCS), depending on the parameters employed.

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    VARIATIONS OF TRANSISTOR PARAMETERS

    • The parameter hfe(β) varies the least of all the parameters of a transistor equivalent circuit when plotted against variations in collector current.

    • All the parameters of a hybrid transistor equivalent circuit increase with temperature.

  • TROUBLESHOOTING & PRACTICAL APPLICATIONS

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    Troubleshooting • In general, if a system is not working properly, first disconnect the ac

    source and check the dc biasing levels.

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    PRACTICAL APPLICATIONS

    • Audio Mixer

    • Preamplifier

    • Random-Noise Generator ! • Sound-Modulated Light Source !

     Report: com3_14_R02_xx Deadline: 17 Nov. @11:59 pm

  • • For more details, refer to:

    • Chapter 5 at R. Boylestad, Electronic Devices and Circuit Theory, 11th edition, Prentice Hall.

    • The lecture is available online at:

    • http://bu.edu.eg/staff/ahmad.elbanna-courses/11966

    • For inquires, send to:

    [email protected]

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    http://bu.edu.eg/staff/ahmad.elbanna-courses/11966 http://bu.edu.eg/staff/ahmad.elbanna-courses/11966 http://bu.edu.eg/staff/ahmad.elbanna-courses/11966 http://bu.edu.eg/staff/ahmad.elbanna-courses/11966 mailto:[email protected]

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