What is Equivalent circuits: Definition and 24 Discussions

In electrical engineering and science, an equivalent circuit refers to a theoretical circuit that retains all of the electrical characteristics of a given circuit. Often, an equivalent circuit is sought that simplifies calculation, and more broadly, that is a simplest form of a more complex circuit in order to aid analysis. In its most common form, an equivalent circuit is made up of linear, passive elements. However, more complex equivalent circuits are used that approximate the nonlinear behavior of the original circuit as well. These more complex circuits often are called macromodels of the original circuit. An example of a macromodel is the Boyle circuit for the 741 operational amplifier.

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  1. cianfa72

    Formal proof of Thevenin theorem

    Hi, I am looking for a formal proof of Thevenin theorem. Actually the first point to clarify is why any linear network seen from a port is equivalent to a linear bipole. In other words look at the following picture: each of the two parts are networks of bipoles themselves. Why the part 1 -- as...
  2. L

    I Equivalence of these quantum circuits

    In the attached image, there are two quantum circuits that are equivalent. I am trying to understand how. Let's call the top qubit ##q_1## and the bottom one ##q_2##, and the outputs ##q_1'## and ##q_2'##. From what I understand, the C-NOT gate doesn't affect the control qubit. Because Hadamard...
  3. R

    Engineering Norton/Thevenin Equivalent circuits with a dependent voltage source

    so when I did this problem I did nodal analysis to find the voltage across the 40k resistor, and found it to be 16V. From there I did two source transformations, combined the sources and did some equivalent resistance to get the answer as seen below: However this differed from the answer he...
  4. adamaero

    Engineering KVL and sensitivity of a simple circuit

    Homework Statement Homework Equations The Attempt at a Solution Note to self - simple diode concept: http://www.cs.tut.fi/kurssit/TLT-8016/Chapter3.pdf#page=5 Unsure about this KVL (above). For the last sensitivity part, equations be falling out of the sky...
  5. S

    Engineering Equivalent Circuits: Why Are They the Same?

    1. Homework Statement Why are the two circuits below equivalent? Homework Equations N/A The Attempt at a Solution Background: I am studying BJTs, and in my textbook the equivalent resistance of resistor 1 and 2 is noted to be in parallel. The text provides no explanation why. In my search...
  6. M

    Engineering What are the implications of Thevenin equivalent circuits on circuit behavior?

    Hiya, this is my first time posting so apologies for any errors in formatting. :oldsmile: I am confused as to whether when Thevenising a portion of a circuit is it to simplify BUT provide the same output characteristics, meaning the workings of the Thevenin part of the circuit may behave...
  7. P

    How to find equivalent circuits

    Hi, I need to learn how to find equivalent circuits using what my textbook calls open circuit and short circuit methods. Thank you all for you support
  8. P

    What Are These Two Equations for Equivalent Capacitor Circuits?

    I do not understand these two equations V[eq][/SUB] = V[in][/SUB] and R[eq][/SUB] = -(V[oc][/SUB] / I[oc][/SUB] ) Your help is much appreciated
  9. H

    What Is a Complemented Voltage Source in an Inverter Circuit?

    Homework Statement [/B] I am studying a book related to digital integrated circuits and there is something I cannot understand. The book starts by explaining two basic building blocks of digital integrated circuits: the inverter and the non-inverter. My question is about the inverter. It...
  10. J

    Engineering Square of resistors within a circuit. What is the equivalent

    Homework Statement Homework Equations -We can re-arrange circuit components into simpler orientations as long as the components' connections to previous nodes are maintained. The Attempt at a Solution -I attempted to re-arrange the loop of three resistors at the upper left region to no...
  11. D

    Engineering How Do You Calculate Thevenin Voltage Using Superposition?

    Homework Statement http://puu.sh/lQPvh/d0efa216ff.png Homework EquationsThe Attempt at a Solution http://puu.sh/lQPAR/2456db4783.jpg http://puu.sh/lQPCJ/f142c25f63.jpg http://puu.sh/lQPER/5eb4af107e.jpg Is this correct? I used principle of superposition to calculate the Thevenin...
  12. T

    Thevenin and Norton equivalent circuits

    Hi guys, Sorry if all you guys think this question is too easy. But I have a hard time to understand how to group the resistor. I suppose to find the the thevenin and Norton equivalent circuit. This is what i think about the combination of resistor. Req1= RL+1k Req2= Req1 ll 3.3k (3.3k after...
  13. EngUOL

    Confused About Transistors: Pi Hybrid & Small Signal Equivalents

    Hi everyone. I am starting to study transisors at Uni. and I am confuse in some main concepts. i thought about posting it here so someone can help me up. are pi hybrid signals equivalent circuits used with the same porposes as small signals equivalent circuits? or are pi hybrid signals, small...
  14. R

    Engineering Why Is Source Transformation Used in Circuit Analysis?

    Homework Statement [/B] Homework Equations There's not much to write here except parallel resistors equation. This is supposed to be a superposition problem. How did he use a source transformation because I have no idea why and where he did the equivalent resistor and why did a current...
  15. A

    Engineering Find T-Network Equiv of ∏ (Pi) Network - AC Equiv Circuits

    Homework Statement Determine the T-network equivalent of the ∏ (Pi) network shown in the Figure? Homework Equations I started working on this question and don't know if I am heading in the right direction. The impedances of the T network (Z1, Z2, Z3) can be found from the impedances of the...
  16. M

    Equivalent Circuits: How Do (a) & (b) Compare?

    How are the circuits (a) and (b) equivalent? i0 is the sum of two currents that flow from high to low potential (flow of positive charge) So why does i0 not flow from high to low pot?
  17. P

    Engineering Thevenin and Norton Equivalent Circuits

    Homework Statement Consider this circuit. Find the Thévenin and Norton Equivalent Circuits (just need the 1st one). Homework Equations The Attempt at a Solution My attempt: Can someone check? Thanks a lot!
  18. S

    Engineering Flip Flops, and equivalent circuits

    Homework Statement Hey guys, Can someone please explain how the following circuits that I attached are equivalent? I'm not seeing that they are when I develop equations for the output Z. For the first one I get Z=Q1+Q2=(Q1'+Q2')+(XQ2')'=Q1'+Q2'+X'+Q2 For the second image I get...
  19. D

    Equivalent circuits resistor problem

    Homework Statement Find Req. Homework Equations Series: R1 + R2 + ... Parallel: 1/(1/R1 + 1/R2 + ...) The Attempt at a Solution There's no solution for this one in the book but I'm thinking that I can break this up into two parallel sets. Parallel1...
  20. A

    Uniqueness and existence of simplified equivalent circuits

    I know this probably sounds weird, but I have a research problem that requires "random" analog circuits. Basically what this means is that I create Spice netlists by randomly adding linear and/or nonlinear components of random types with random node and parameter values. This works fine and I...
  21. S

    Thevenin Equivalent Circuits with Dependent Source

    May anyone please help with the method of getting Thevenin Equivalent resistance (RTH) for the attached circuit. I have already found VTH to be 8V. Sim
  22. S

    Thevenin and Norton Equivalent Circuits problem

    Hi, I found this question from a textbook: Suppose there are two black boxes, Box A has a 1V voltage source and 1ohm resistance (Thevein Circuit); and Box B has a 1A current source and 1ohm resistance (Norton Circuit). You only have access to the two terminals. How do you know which is which...
  23. B

    Why Does Magnetic Hysteresis Loss Appear as a Resistance in Electrical Circuits?

    Hi Guys, :smile: Can someone please explain to me the logic behind the representation of 'Magnetic Hysteresis loss' as a resistance in electrical equivalent circuits?... will be extremely grateful. I have studied some info on this subject on the net. Even though the physics of Hysteresis...
  24. B

    Representation of magnetic hysteresis loss as a resistance in equivalent circuits

    Hi Guys, :smile: Can someone please explain to me the logic behind the representation of 'Magnetic Hysteresis loss' as a resistance in electrical equivalent circuits?... will be extremely grateful. Thanks & Regards, Shahvir