What is Current source: Definition and 136 Discussions

A current source is an electronic circuit that delivers or absorbs an electric current which is independent of the voltage across it.
A current source is the dual of a voltage source. The term current sink is sometimes used for sources fed from a negative voltage supply. Figure 1 shows the schematic symbol for an ideal current source driving a resistive load. There are two types. An independent current source (or sink) delivers a constant current. A dependent current source delivers a current which is proportional to some other voltage or current in the circuit.

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  1. G

    Power generated by this current source

    Figure: My attempt at a solution: 1st kirchoff law: $$J=2I_0+I_0=6\, \textrm{A}$$ $$V_1+8=10\rightarrow \boxed{V_1=2}$$ $$V_1=6-V_S\rightarrow \boxed{V_S=-4\, \textrm{V}}$$ We are looking for ##P## generated in ##J## $$V_J=V_1-2\cdot J=2-2\cdot 6=-10\, \textrm{V}$$...
  2. 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...
  3. PhysicsTest

    Voltage source and current source

    As per ohms law the current is generated based on voltage and resistance V=IR. So if 5v and 1k resistor the current 5mA flows in resistor. But if I take a current source, can I pump any amount of current to resistor? So, current drawn is not characteristic of resistor?
  4. X

    Engineering Find di/dt and dr/dt for a DC circuit with indepedent current source

    Dear PF, I am trying to solve practice problem 8.2. I am stuggling with part B of the question which asks us to find diL(0+)/dt, dvC(0+)/dt and dvR(0+)/dt. My attempt can be seen below. Before t=0 the 4A current source is not present and thus it is an open circuit. A capacitor acts as an open...
  5. paulmdrdo

    Finding the output impedance of Current Controlled Current Source

    Summary:: I was trying to derive the equation for the output impedance of the ICIS circuit. Here's what I've tried so far. What I have derived does not agree with the one provided in my book. Since it is a current source the negative feedback must increase the output impedance. The one I...
  6. W

    How to find the current and voltage in a circuit with current sources?

    Summary: Facing a circuit with 2 parallel resistors and 2 current sources (1 dependent, 1 independent). Trying to find the current, voltage, power delivered by the independent current source and power delivered by the dependent current source. I'm trying to start by finding the current i0 but...
  7. fight_club_alum

    Determining the voltage polarity of the independent current source

    I am so sorry if I am posting this in the wrong forum; it is just not a homework problem, and I can't find the right place - it's more of a study help question.
  8. F

    Implement a DC current source - simulink

    Homework Statement Homework Equations - The Attempt at a Solution Here's my work : When I add the DC current source , it shows a red dotted line and won't connect to other elements . Any help would be greatly appreciated !
  9. Abdullah Almosalami

    Constant Current Source in Driving an RC Circuit

    Alright. So I'm getting two different solutions depending on how I look at this problem, and I know one is correct but I don't know why the other would be incorrect. So, given this general circuit of a constant current source driving an RC circuit in parallel: Now, what they tell me in class...
  10. S

    Three-part Problem: Thevenin + Dependent current source

    Homework Statement The diagram of the electric circuit, the problem statement (and an attempt) are included in the file below.: https://www.docdroid.net/RD0ZEgA/question-3.pdf Homework Equations Dependent Current Source Nodal analysis Short Circuit Current Thevenin Voltage Thevenin...
  11. A

    Treating an inductor as a current source?

    https://imgur.com/a/Yb2vpmp why can the inductor be treated as a 1A source?
  12. ESMAT 1995

    Constant current source Inverter

    i was reading about CSI and the first paragaph said "A constant current source is assumed here, which may be realized by using an inductance of suitable value, which must be high, in series with the current limited dc voltage source. " and it says nothing else about it , so clearly it's a basic...
  13. Akmalidin

    Constant Current Source for high current

    Hi, I am building a charger for my bicycle front and tail light that uses dynamo to charge them while cycling. However, depending on my speed, current is fed differently to lights and they start to flicker. Therefore, I was wandering if there is a way to make a constant current source which...
  14. Bassa

    Initial Voltage in an RC circuit with a Current Source and no Voltage Source

    Homework Statement [/B] Derive an expression for vc(t) in the circuit of Figure P4.13 and sketch vc(t) to scale versus. I attached a screen shot of the circuit for this problem. time. Homework Equations V = IR V = V0exp(-t/tau) The Attempt at a Solution [/B] I am trying to find the...
  15. E

    Superposition with AC voltage source and DC current source

    Homework Statement Using the superposition principle, determine the current i(t. 2. Homework Equations Zc = 1/jwC Zl = jwL V = I*R I = V/Z The Attempt at a Solution First, I converted inductor/capacitor to impedance: L = 1.5H -> jwL = j * 10 * 1.5 = 15j C = 10mf = 1/(jwC) =...
  16. Aleksa Stanojlovic

    Norton Equivalent with dependet current source - Problem

    Hey everyone... I've tried to solve this problem with all kind of methods ,but I couldn't do it. I have tried to make an open circuit between R2 and R2 and then to find thevenin voltage and Ri but I have problem solving for thevenin voltage because of this dependent current source... Please give...
  17. Marcin H

    Engineering Thevenin & Norton Circuit with Current source?

    Homework Statement Homework Equations V=IR Thevenin/Norton The Attempt at a Solution I am trying to find the Voc, but this circuit isn't making sense to me. So to start we can ignore the 9ohm resistor and that branch for now when Finding Voc so you are basically left with the square...
  18. M

    HVDC - Current Source Converter - Minimum DC Power flow

    Hello, I was reading about the differences between Current Source Converters and Voltage source converters. One main difference was that Current source converters need to have a minimum DC power flow of 5-10% while VSC do not have a min flow requirement. It was also called a deadband. Why is...
  19. YellowBelliedMarmot

    Engineering Finding the Current Source of an RLC AC Circuit

    Homework Statement Homework Equations V=IZ[/B] Zc = 1/(-jwc) Zl = jwc w = 2(pi)*f The Attempt at a Solution I'm teaching myself circuit analysis, and it's been rough. Ultimately, I been able to mostly figure everything out, but I've ran into a wall with AC. The main problem I am having...
  20. K

    Current limiter for TIA, realizing dc current source

    Problem: my photo diode receives pulses of width 10ns-150ns and repeating at rate of 1Hz-50KHz the current from photo diode depending on incident light can go from 10nA-100mA, so i have two photo diodes to cover the dynamic range, what i want to do is limit the current from a photo diode to...
  21. goonking

    Engineering RC circuit with current source

    Homework Statement Homework EquationsThe Attempt at a Solution so when t=0, the capacitor is a closed circuit. The Req of the circuit is (20k)(30k)/(20k+30k)= 12000 ohms. U = I Req = (7.5x10-3A) (12000 ohms) = 90 Volts so there is a voltage drop of 90 volts across the 20k resistor (R1)...
  22. M

    Power Source, Current Source and Resistor in parallel

    Homework Statement Consider the circuit shown in Figure P1.68. Find the current i_R flowing through the resistor. Find the power for each element in the circuit. Which elements are absorbing energy? V_source=12 V I_source=4A R=8 ohms Here is a picture of 1.68 Homework Equations P=IV...
  23. Marcin H

    Voltage vs. Current Sources: Understanding the Differences

    Homework Statement Check picture Homework Equations V=IR The Attempt at a Solution I thought I had this right, but then I started thinking about it and I'm not sure anymore. My thought was since the voltage was changing and the current was constant, that the source was a voltage source. I...
  24. hdp12

    Engineering Given RLC circuit to find V over load & other complications

    Homework Statement In my Intro to EE class we have a homework assignment with the following problem: I think I finished part a but want to make sure that I am doing the problem correctly before I move on to the next part. Homework EquationsThe Attempt at a Solution
  25. J

    Circuit analysis current source problem

    Homework Statement given the circuit shown, find V1. Homework EquationsThe Attempt at a Solution see image: am i right? Video says otherwise... I chose to use the superposition theorem here. help appreciated, regards, james.
  26. dep0

    What is the Voltage Drop across a dependent current source?

    Hello, I want to calculate the Thevenin/Norton equivalent of a circuit with a dependent current source. I tried to analyse the circuit using loop equations but i don't know how to calculate the voltage drop across the current source. Any help would be appreciated.
  27. S

    AC Current Source: Build an Op-Amp Circuit for µA RMS

    Hi everybody, As part of my research at UCSD, we are trying to measure Hall resistance of some materials. And to do that we need to send an AC current. So I wondered how we could easily build an ac current source, probably based on op-amp. I know there is the Howland circuit (current pump), but...
  28. ichabodgrant

    Engineering Circuit with 2 voltage sources and 1 current source

    Here is the circuit. I have to find the voltage across each resistor and the current i1 and i2. My attempts are the following: By KCL, i2 + i1 = 0.1 A By KVL, 3 - 5 - 100i1 + 1100i2 = 0 ∴ i1 = 0.09 A, i2 = 0.01A ∴ Voltage across 100Ω resistor = 0.09 × 100 = 9 V, voltage across 1100Ω resistor...
  29. C

    V-i characteristics for voltage divider with current source

    This is a problem from Foundations of Analog and Digital Electronic Circuits by Agarwal & Lang, I'm going through it by myself, I'm not in a course, so I'm depending on you friendly forum people for help! I really like this book but it has a lot of errors, perhaps this is another error. 1...
  30. N

    Engineering Coupled RC circuits with AC current source

    Homework Statement Hi, I already asked a question close to this, but now I have different conditions. This is the circuit C_1 = C_2 \\ R_1= R_2 The current is an AC , and I would like to know the voltage at R_1 and at R_2 I made some progress but I do not really know hot to continue...
  31. D

    How does a current source work in Norton's Therom

    Hi.i know that a ideal current source has infinite resistance and it supply's constant current to aload connected across it. The current source doesn't have the infinite resistance in series to it but in pparalle. All is well until I think of this Norton's Therom. When we transform a voltage...
  32. N

    Voltage drop over an independent current source?

    Homework Statement I am supposed to give a thevenin equivalent circuit to the one posted in the picture. Homework Equations V=IR KVL: "voltage drops around a closed loop sums to zero KCL: "current into a node equals current out of a node" The Attempt at a Solution The part I'm confused...
  33. N

    Current Source in Parallel with Short Circuit

    Homework Statement Which of the following are self-contradictory combinations of circuit elements? - A 2 Amp current source in parallel with a short circuit. Homework Equations KVL- "the sum of voltages around a closed loop amounts to 0. KCL- "the current into a node equals the current out...
  34. A

    Van de graaff generator as a current source

    I know that van de graaff generator is a high voltage generator, i was wondering though if we can use it as a current source, if we get any resistor, connect the negative terminal to the generator "if the generator generates negative charge " then ground the positive terminal, then any charge...
  35. Ramana

    Constant current source using digital potentiometer

    Hello Everyone, Best wishes Am new to this forum. Please need a brand new suggestion for digitally controlled constant current source. I am designing this circuit for Plating thickness measurement. I have tried a several circuits based on Analog pot but would be helpful if i get with Digital...
  36. A

    Independent Current Source In Series With Resistor

    Homework Statement Write the KVL Equation for the outer loop Homework EquationsThe Attempt at a Solution The question above is a sample I have made for such a condition. The goal is not to find the value, but only write the correct equation. If an independent current source is connected in...
  37. N

    Circuit consists only of voltage source and current source

    This is more of a theory question than a homework question...but could a circuit consist solely of a voltage source and a current source? What I mean is a very simple circuit with a voltage source of Vx and a current source of Ix, connected in series. No resistor anywhere. Could this work? And...
  38. E

    Indeoendent current source in series with a resistor

    Guys, this seems very trivial yet I can not come to the correct answer and I've searched everywhere. I am asked to find the node voltages using nodal analysis. The trouble is I don't know how to express a current in a brach between 2 unknown voltages where there is an independent current...
  39. H

    How Does Current Source Relate to the Battery?

    How can current source be implemented? I think the source of current is the battery itself (due to potential difference). Plus current source has its own symbol. If battery is the source of current then does current source refer to the battery?
  40. A

    Engineering Circuit theory -- Current source, voltage source, resistor in series

    Homework Statement the voltage Vc in the figure is always equal to 2 Relevant equations The Attempt at a Solution From kirchhoffs law, -Vc+4+5=0 Vc=9 V will Vc always equal to 9 V or it will vary?
  41. P

    Circuit with 1 independent current source

    Hi I've tried to solve the following circuit using Kirchoff's laws but i get wrong results.I know that because I've got a different solution of the same excercise.I've attached the image.My question is what are the equations of Kirchoff's laws because I try this over 2 hours and I can't figure...
  42. mishima

    Constant current source advice

    Some of my advanced chemistry students would like to try this pharmacokinetic model circuit outlined in an AAPT publication (Cock & Janssen, The Physics Teacher, Volume 51, Issue 8, pp. 482-484 (2013)). It is a simple RC circuit, but I've never built a constant current source and am unsure of...
  43. D

    How Do Constant Current Sources Differ From Other Power Sources?

    How are constant current sources different than any other source? Also, would they really have a constant current in any situation? Even when back-emf is induced? Can anyone explain the use of a constant current source, and how different they are from other sources?
  44. J

    Understanding Current Sources: Device or Electrical Object?

    Which is the real interpretation for current source? Exist some device or electrical object that acts like a current source?
  45. H

    Constant current source design

    Hey guys, I have been trying to design a constant current source that has a digitally controllable (μcontroller) range of maximum current outputs. Ideally the source would be able to be adjusted from .25mA to 2mA. The input voltage for the source would be in the range of 9 to 14 volts. Also I...
  46. gfd43tg

    Thevenin equivalent with dependent current source

    For this problem, I added in an external source, and found an expression for the external current in terms of ix. Then I divided Vex/iex to get the Rth. Then I did superposition to find the Vth. I had some troubles getting rid of the extra currents, particularly i3 and i2. I was wondering if...
  47. dwn

    Engineering RL Circuit with current source

    Homework Statement Image Homework Equations Current divider The Attempt at a Solution The only thing I see is that I solve for R1 and R2 for t < 0. Other than that I'm confused and not even sure I'm right about solving t<0.
  48. dwn

    Parallel RC with current source

    Homework Statement See images In the first image, I made a circuit with the switch closed and then two when the switch is opened. The bottom circuit is the Thev transform. Homework Equations The Attempt at a Solution Let me first explain my understanding of the circuit. Prior to t = 0, the...