1. Lecture 361 Thevenin Equivalent Circuits

2. Lecture 362 Review: Independent Source(s) Circuit with one or more independent sources R Th V oc + - Thevenin equivalent circuit

3. Lecture 363 Review: No Independent Sources Circuit without independent sources R Th Thevenin equivalent circuit

4. Lecture 364 Finding the Thevenin Equivalent I-V characteristics are straight lines (a consequence of the linearity of resistor models). Circuits with independent sources: –Intercepts are v oc (t) and i sc (t) Circuits w/o independent sources: –Slope is R Th

5. Lecture 365 No Independent Sources v(t)v(t) i(t)i(t) Slope is R Th

6. Lecture 366 Finding R Th With no independent sources, V oc and I sc are both zero. To find the slope, we apply a test source with a given voltage (or current) and measure the current (voltage) produced by the source. This gives the slope of the I-V line.

7. Lecture 367 Example: CE Amplifier 1k  V in + - 2k  +10V + - VoVo

8. Lecture 368 Small Signal Equivalent 1k  V in 100I b + - VoVo 50  IbIb 2k  + -

9. Lecture 369 Thevenin Equivalent @ Input 100I b 50  IbIb 2k  R Th

10. Lecture 3610 Apply a Test Current Source 100I b 50  IbIb 2k  1mA + - VxVx

11. Lecture 3611 Solve for Vx Use Nodal Analysis 100I b 50  IbIb 2k  1mA VxVx V1V1

12. Lecture 3612 Solve for V x

13. Lecture 3613 Compute R Th

14. Lecture 3614 Apply a Test Voltage Source 100I b 50  IbIb 2k  1V + - V1V1

15. Lecture 3615 Solve for I b

16. Lecture 3616 Compute R Th

17. Lecture 3617 AC Steady State Thevenin’s theorem also applies to AC steady state analysis. An arbitrary linear circuit can be replaced by an equivalent source and impedance. The determination of source and impedance values is essentially the same as for resistor circuits.

18. Lecture 3618 Independent Source(s) Circuit with one or more independent sources V oc + - Thevenin equivalent circuit

19. Lecture 3619 No Independent Sources Circuit without independent sources Z Th Thevenin equivalent circuit

20. Lecture 3620 Example: IC Interconnects 0.07pF 500  VsVs + - 15  0.07pF Find the Thevenin equivalent circuit:

21. Lecture 3621 Find Impedances, then V oc and I sc  = 10 10 500  VsVs + - 15  -j1.43k 

22. Lecture 3622 Source Transformations 515  15  -j1.43k 

23. Lecture 3623 Source Transformations Cont. 15  -j1.43k  + - 455  -j164 

24. Lecture 3624 Source Transformations Cont. 15  -j1.43k  470  - j164 

25. Lecture 3625 Source Transformations Cont. 15  -j1.43k  348  -j250  + - + - V oc

26. Lecture 3626 Source Transformations Cont. -j1.43k  363  -j250  + - V oc

27. Lecture 3627 Source Transformations Cont. 251  -j267  + - V oc + -

28. Lecture 3628 V oc V oc = (0.446-j0.503) V s

29. Lecture 3629 I sc I sc = (0.00184-j0.00005) V s

30. Lecture 3630 Z Th