Circuit analysis Definition and 569 Threads

A network, in the context of electrical engineering and electronics, is a collection of interconnected components. Network analysis is the process of finding the voltages across, and the currents through, all network components. There are many techniques for calculating these values. However, for the most part, the techniques assume linear components.
Except where stated, the methods described in this article are applicable only to linear network analysis.

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  1. Ineedhelpwithphysics

    Finding parallel or in-series resistors

    I cannot understand why the 45 ohm resistor is parallel to the 15 ohm resistor. It's been defined that if two or more resistors are in parallel they same common connection points. I don't see these connections points. Is the junction point after the ammeter signifying that the 45 ohm and 15 ohm...
  2. E

    Confusion about applying Faraday's law to a circuit

    If all electric fields generated by electrostatic charges, then we know $$\oint_C {E \cdot d\ell} = 0$$ so in the following circuit, $$\oint_C {E \cdot d\ell} = -V+IR = 0$$ In cases where not all electric fields generated by electrostatic charges, then according Faraday's law, we know...
  3. BuggyWungos

    Why is current constant through a resistor?

    I understand that the current in the top wire above A will be the same as the wire just below A, as it will be for the wire region marked by n to m, due to the fact that all current in equals all current out. My confusion lies in the first equation I supplied, the change in voltage through the...
  4. E

    I Electric Potential in circuit

    I reviewed some of the fundamental physics and I looked back at the equation for Electric potential at a point p: $$V(p) = k \sum_{i} {\frac {q_i} {r_i}}$$ where - p is the point at which the potential is evaluated; - ri is the distance between point p and point i at which there is a nonzero...
  5. E

    Engineering Unable to model Transresistance amplifier with feedback correctly

    I spent the whole day trying to figure why transresistance amplifier modelled with z-parameters does not match with nodal analysis results but I sill can't figure out. I desperate need help on this... I write down step by step what I did for a very simple transresistance amplifier here and hope...
  6. E

    Engineering H-parameter model for non-inverting amplifier

    For a standard non-inverting amplifier as below: With nodal analysis, I got $$\frac {v_o} {v_i}=\frac {R_EZ_o+aZ_iR_E+aZ_iR_f} {R_ER_f + R_EZ_i + R_EZ_o + R_fZ_i + Z_iZ_o + R_EaZ_i}$$ However, with the feedback network of the amplifier converted to a h-parameter network as below: With nodal...
  7. E

    Engineering Negative PSRR of the Two-Stage Op Amp

    From page 4-9 of this lecture note https://pallen.ece.gatech.edu/Academic/ECE_6412/Spring_2004/L180-PSRR-2UP.pdf, it gives example on how to model a Two-Stage Op Amp to find the PSRR- when VBias is connecting to ground as oppose to when VBias is connecting to Vss. One thing I don't understand is...
  8. E

    DC input random offset voltage for diff. amplifier with current-mirror load

    I am trying to figure out how the derivation of equation 6.69 come about on page 426 in the book Analysis and Design of Analog Integrated Circuits, 5th Edition by Gray and Meyer. They defined on page 424 under section 6.3.3 the input offset voltage (VOS) of op amps with differential inputs and...
  9. E

    Time domain equation for RC circuit with AC input

    TL;DR Summary: How to find Time domain equation for RC circuit with AC input from inverse laplace transform For a simple RC circuit with AC input such as this: https://www.electronics-tutorials.ws/wp-content/uploads/2013/08/rc12.gif?fit=310%2C151?fit=310,226. If the AC input is just a simple...
  10. E

    Voltage gain of a bipolar transistor circuit

    For a simple bipolar transistor above, base-to-collector voltage gain ≈ -gm*Rc/(1+gm*Re) < 0, base-to-emitter voltage gain ≈ 1 > 0, should emitter-to-collector voltage gain ≈ -gm*Rc/(1+gm*Re) * 1 < 0. How come it is equal to gm*Rc > 0?
  11. ZoeDale

    Engineering Analyzing this operational amplifier circuit with DC

    Hi all, I attached my attempt at a solution in the attached picture. I am using the textbook titiled as ”electronic circuit analysis“ by David E. Johnson, and op amp is in chap 3; while I did not find any example that attach the Vee and Vcc with amplifier . It seems that v+ = v- doesn’t hold in...
  12. milkism

    Complex RLC Circuit Problem (System of diff eqs)

    The following circuit is: Going clockwise the current ##I_1## goes through resistor ##R_1## and voltage ##V_11##. Current ##I_2## goes through capacitator ##C_1## and ##R_2##. Current ##I_3## goes through resistors ##R_3## and ##R_4##. Current ##I_4## goes through resistor ##R_5##, but from...
  13. T

    Connect parallel batteries with wrong poles

    I would like to do now (theoretically) a couple of rather naive things with two batteries with voltages ##V_1## and ##V_2## in parallel charged with an abstract load with resistance ##R##. Usually, one learns in elementary electronics that the only "right" configuration with batteries in...
  14. vord_ler

    How to find current direction when analysing a cricuit using KVL, KCL

  15. Z

    How is KVL used in the node method KCL equations?

    Consider the following electric circuit in which we have node voltages labeled I have a question about the reasoning present in the book I am reading about the node method of circuit analysis. If we write KVL equations around the loops we get $$-V+(V-e)+e=0$$ $$-e+e=0$$ Then I don't...
  16. Wrichik Basu

    Laplace transform vs phasor analysis in circuit analysis

    I recently acquainted myself with Laplace transform, and it appears that it has some relations with phasor analysis. This observation stems from the fact that while in Laplace transform, we have ##s = \sigma + j \omega## as the variable, in phasor analysis, we just use ##j\omega,## apparently...
  17. JMFernandez

    Question about this Capacitor voltage integral equation

    Hi. I don´t know if this question should be in the maths forum, but as it´s related with circuit analysis, I will post it here. I just would like to know how you get: v(t) = 1/C ∫tt0 i(τ) dτ + v(t0) From: v(t)=1/C ∫t-∞ i(τ) dτ I just know the basics of calculus and I don´t know how to...
  18. PhysicsTest

    Phase Current Sensing Circuit: Q&A

    This is the phase current sensing circuit Here the phase currents are converted to voltages by passing through shunt resistor and fed to the opamp. Two questions i have a. Can I analyze the R45, R37, C26 as one filter circuit and the remaining as other circuit for gain? b. The phase currents...
  19. Muhammad Usman

    I Physics domain analysis of Voltage drop in series resistor

    Hi all, I apologize if its a very basic question but this is related to my quest to know the things deeply. And it is not homework help at all, it is just a general question. The main question or objective to ask this question is to understand what is actually happening in a circuit with one...
  20. M

    Engineering Analyzing the switch circuitry for an HF Amplifier

  21. cianfa72

    Write Down Loop-Impedance Matrix for Current-Controlled Current Sources

    TL;DR Summary: How to write down the loop-impedance matrix in case of Current-Controlled Current Sources Hi, as in the following linear network, I would like to write down the loop-impedance matrix for it where there is a CCCS ##2i_1## source. The starting point is the network elements...
  22. ubergewehr273

    Measuring the inductance of a micron feature size gold coil

    Hi all, I recently fabricated a bunch of gold coils patterned onto a glass substrate and am in need of measuring the inductance of these samples. Since the feature size is in microns, I can't exactly use an RLC meter. At the moment, I'm trying to build an LCR series circuit with a PCB and...
  23. S

    Circuit analysis via polyhedron

    (NOTE: I should state that my circuit analysis knowledge is up to the level of a single comprehensive EE course, as per ME students.) I was thinking about the famous resistor cube problem, and I've come up with some observations: - Every branch (I think that's the term - i.e., a branch is any...
  24. G

    Capacitor Circuit Analysis: How to Find Voltage Across Resistors

    Figure: My attempt at a solution: Once the capacitors have been applied, we see directly that ##\boxed{v_c=v_0=0\, \textrm{V}}## Wouldn't this one be done like this? I know the following: in a circuit with capacitors and coils, if we have Capacitor: we change for an open circuit. Coil: we...
  25. A

    Are Overly Complicated Homework Problems Beneficial for Student Learning?

    Hello I'm trying to solve my homework assignment, I have successfully found the thevenin resistance which is equal to 3.75 but I'm stuck on how to even get started to find the voltage because there are too many components. I have shorted the load resistor which is called RL but there are too...
  26. Purpleshinyrock

    Engineering Need help answering questions (Voltage source and 3 Resistors)

    Hello. I need help arriving to the answers to the following question above. You will find the circuit attached for Number 1 I though that crrent would be maximum when resistance is replaced with a wire but I couldn't get a an expression for ut. as for question number 2 I tried applying node...
  27. Purpleshinyrock

    Engineering How do I find Vth with the node voltage method?

    Hello. I'am practicing circuit analisis about the norton and thevenin's circuits and I can't seem to manage to get the right thevenin's voltage using the node voltage for a) resolution 1) I did source transformation turning the current source(2A) into a voltage source (10V) applied node voltage...
  28. johnsmith7565

    Engineering First Order RL Circuit: Finding a Current I2(0-)

    I shorted the inductor and performed mesh analysis. The solutions to the linear system were done using a calculator. The book says that the value for i2(0-) should be 15 mA but I'm getting -2mA. What am I doing wrong? I'm completely confused. Maybe mesh isn't the most efficient way to find I2...
  29. Purpleshinyrock

    Engineering Circuit analysis on a supernode

    Hello. Can someone give m e pointers on how to find the value of vx given that it is inside a supernode(will it be the valueof the voltage inside or the difference of potential between the two nodes?): here's the exercise and what I've done so far attached. Your time and attention are deeply...
  30. altruan23

    Engineering Why is a differential amplifier considered the same as a subtractor?

    So after using superposition and setting the ratio R2/R1 = R4/R3 the same or R2=R4 and R1=R3,i come to the eq. for output voltage Vout= R2/R1 * (V2-V1) or R4/R3(V2-V1). And in the book foundations of analog and digital electronics by agarwal and lang, they are saying that this circuit is a...
  31. altruan23

    Engineering Opamp adder circuit: Where does the "-" come from?

    So i used KCL and both currents are flowing into the node, and then leaving together to go to the resistor R3. So my eq can be seen in the picture. I was looking in a book and they had a minus infront of the parantheses. Is the current flowing from R3 into the node??
  32. altruan23

    Engineering OPamp circuit - how to simplify this term?

    So this is the circuit. And here i tried to calculate Uout/ Uin , any suggestion how to simplify this term?? I used Uout= Uin * (1+ Z2/Z1)
  33. altruan23

    Engineering Constant current source transistor circuit - differences between 2 types?

    So basically we can have a constant current but i don't understand this circuit. for example: i can have the Ia what ever I want with current divider rule: Ia = Iq * R2/R3. So Ia is proportional to the ratio of R2/R3. And if i give a resistor at the collector terminal, if i change it between...
  34. altruan23

    Engineering Op amp circuit -- Did I calculate the output voltage correctly?

    can someone check, if i calculated the output voltage correct? i used virtual ground because V+-input of the op amp is 0 --> V- input is then also 0.
  35. altruan23

    Simple voltage divider -- why does this work?

    Summary:: don't understand how can we use a voltage that has been already dropped. I don't understand the voltage divider. So R1 and R2 are the same. I have 10 V in beginning, then 5V drop across R1 and then i have 5V drop across R2. But how can I use the 5V if they already dropped at R2? If...
  36. altruan23

    Engineering Black box which contains 5x 1ohm resistors

    You are given a black box with three terminals, as shown below. The box is known to contain five 1-ohm resistors. Using an ohm-meter, you measure the resistance between the terminals to be the following: A - B: 1.5 ohms B - C: 3 ohms A - C: 2.5 ohms Determine the configuration of the five...
  37. NoahCygnus

    How to use Kirchhoff's voltage law on this circuit?

    In this circuit, I have to find the potential at point O. I tried using Kirchhoff's voltage law for the three open loops AOC, AOB and BOC to arrive at potential at O. According to my calculations the potential at O should be 0, but that is not the case according to the source. So I must be using...
  38. T

    Superposition Principle for two Voltage Sources (confusions about....)

    I have a question about natural limitations when the superposition principle for circuits is applicable. Possibly there is a quite elementary reason why the problem I'm going to present next fails, but up to now I haven't a precise reason why that's exactly the case. Could somebody help...
  39. Tobias Holm

    Find frequency such that two components have same average power

    (This is my first time posting here, sorry in advance for any difficulties. ) All componenets of same type has same magnitude, so e.g. the two resistors both have $R$ resistance. Given the difficulty of the previous exercises, I believe I'm over complicating the problem. However, here is what...
  40. Franklie001

    AC circuit analysis involving resistors and inductors

    Summary:: Hi anyone can explain me how to solve this circuit, finding the current I2 and I1? Really don't know where to start Thanks
  41. T

    Receiver Circuit Question -- What role does this antenna capacitor play?

    Which role plays an additional capacity in a receiver circuit between the antenna and the matching-box part like in this example (found in https://www.frostburg.edu/personal/latta/ee/twinplex/schematic/twinplexschematic.html): Is it necessary for this receiver circuit or just optional? What...
  42. Pouyan

    Which lamp is dimmed in the circuit?

    The true answer is B. But I don't understand why! I know: Kirchhoff's circuit laws : ∑In=0 If we assume that a current that goes from plus to minus, before it passes through lamp B, I know that according to Kirchhof's laws, part of the current will pass through the bottom path where there is...
  43. Xiao Xiao

    Engineering Electric Circuit Analysis of this First Order R-L Circuit

  44. Xiao Xiao

    Engineering Finding Vc for two circuits, Electric Circuit Analysis question

  45. Tim86

    DC current through a resistor circuit

    Summary:: Current through a certain resistor in a mixed dc circuit. Hi, Sorry if this is the wrong forum. I'm trying to work out the current through R1.The answer I need is 2 Amp, which I have confirmed with a simulation software. I have calculated the source current as 8A, the current past...
  46. R

    Circuit Analysis Theorem For the Number of Independent Equations

    I attached a screenshot of the book (sorry no pdf available for this book). Right above the somewhat central line they give the theorem that if there are m currents and n nodes, then there will be n - 1 independent equations from the current law and m - n - 1 from the voltage law. I count 4...
  47. M

    I Checking for negative feedback in a circuit

    This is the circuit in question. During lecture, when checking whether this was negative feedback, my instructor said that if the v_out increases, then v- increases as well, which would lead to the next v_out decreasing because v_out = A(v+ - v-). I get how if v- increases the next v_out would...
  48. R

    Confused about a Result (Circuit Analysis)

    The problems I am referring to are problems 4-10 and 4-11. There is no solution provided for 4-10, so I want to check my answer here. However, I don't understand the answer to problem 4-11. Shouldn't it also be 24 V since it is in parallel with the 200 k##\Omega## resistor? I am actually...
  49. Xiao Xiao

    Electric Circuit Analysis, Nodal Analysis and finding Voltage.

    Summary:: The image shows two circuits, in the first one, using Nodal Analysis we find that V1=4.8V, but in the second circuit V1=10 because using KCL - 10+V1=0. I understand what happened in the first circuit, but I don't understand what happened in the second one, they look the same to me...
  50. Xiao Xiao

    Engineering Help in Electric Circuit Analysis -- One current source and a resistor network

    o9
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