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Methods of Analysis

Methods of Analysis. Instructor: Chia-Ming Tsai Electronics Engineering National Chiao Tung University Hsinchu, Taiwan, R.O.C. Contents. Introduction Nodal Analysis Nodal Analysis with Voltage Sources Mesh Analysis Mesh Analysis with Current Sources Nodal Analysis vs. Mesh Analysis

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Methods of Analysis

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  1. Methods of Analysis Instructor: Chia-Ming Tsai Electronics Engineering National Chiao Tung University Hsinchu, Taiwan, R.O.C.

  2. Contents • Introduction • Nodal Analysis • Nodal Analysis with Voltage Sources • Mesh Analysis • Mesh Analysis with Current Sources • Nodal Analysis vs. Mesh Analysis • Applications

  3. Introduction • Nodal Analysis • Based on KCL • Mesh Analysis • Based on KVL • Linear algebra is applied to solve the resulting simultaneous equations. • Ax=B, x=A-1B

  4. Nodal Analysis • Circuit variables = node voltages • Steps to determine node voltages • Select a reference node, assign voltages v1, v2,…, vn-1 for the remaining n-1 nodes • Use Ohm’s law to express currents of resistors • Apply KCL to each of the n-1 nodes • Solve the resulting equations

  5. Symbols for Reference Node (Ground) Used in this course

  6. Case Study Assign vn

  7. Nodal Analysis with Voltage Sources • If a voltage source is connected between a nonreference node and the reference node (or ground) • The node voltage is defined by the voltage source • Number of variables is reduced • Simplified analysis

  8. Supernode Continued • If a voltage source is connected between two nonreference nodes • The two nodes form a supernode • Apply KCL to the supernode (similar to a closed boundary) • Apply KVL to derive the relationship between the two nodes

  9. Case Study with Supernode

  10. Example 1

  11. Example 2

  12. What is a mesh? • A mesh is a loop that does not contain any other loop within it.

  13. Mesh Analysis • Circuit variables = mesh currents • Steps to determine mesh currents • Assign mesh currents i1, i2,…, in • Use Ohm’s law to express voltages of resistors • Apply KVL to each of the n meshes • Solve the resulting equations

  14. Continued • Applicable only for planar circuits • An example for nonplanar circuits is shown below

  15. Case Study

  16. Mesh Analysis with Current Sources • If a current source exists only in one mesh • The mesh current is defined by the current source • Number of variables is reduced • Simplified analysis

  17. Excluded Supermesh Continued • If a current source exists between two meshes • A supermesh is resulted • Apply KVL to the supermesh • Apply KCL to derive the relationship between the two mesh currents

  18. Example 1

  19. Example 2 Supermesh

  20. Supermesh Example 3 • Applying KVL to the supermesh • Applying KCL to node P • Applying KCL to node Q • Applying KVL to mesh 4 4 variables solved by 4 equations

  21. How to choose? • Nodal Analysis • More parallel-connected elements, current sources, or supernodes • Nnode < Nmesh • If node voltages are required • Mesh Analysis • More series-connected elements, voltage sources, or supermeshes • Nmesh < Nnode • If branch currents are required

  22. Applications: Transistors • Bipolar Junction Transistors (BJTs) • Field-Effect Transistors (FETs)

  23. Bipolar Junction Transistors (BJTs) • Current-controlled devices

  24. DC Equivalent Model of BJT

  25. Example of Amplifier Circuit

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