Questions tagged [current-source]

An electronic component that sources current - if it sinks current it is called a current sink but both devices (sinks and sources) can be called sources. An IDEAL current source will supply current , maintain high voltage compliance (i.e. adapt it's output voltage to match the network it is supplying current to) and have an infinite output impedance. In non-ideal implementations current sources have limited operating ranges and finite output impedances.

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57 views

Working of op-amp based current source

Can anyone please explain me the working of the circuit attached? I believe the op-amp U1 is connected to provide a stable DC voltage at the non inverting terminal of U3. Is my approach correct? The ...
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Problems regarding KCL & KVL

Question: Below figure represents an approximate equivalent circuit of a field effect transistor amplifier. Using KCL find the output voltage \$v_2\$ in terms of input voltage \$v_1\$. My try: I ...
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Oscillations in parallel-RLC network with a limiting VCCS

Here is a parallel-RLC network (where G = 1/R is the admittance) with a limiting VCCS. The characteristic of the VCCS is shown in Fig (b), where the slope is G1. The problem asked is as follows: Find ...
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How can I make a current source that can supply 1uA?

Is there anyway I can make a constant current source which has an output of 1uA or can I get it from the market? The load is around 200kOhms, and I need accuracy to 1%.
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Why can we bias MOSFET with current source?

My question is: If I have properly set VGS to prevent MOS from turning off, then if we biase a MOSFET with a constant current source, how can we conclude that it is working at saturation region? How ...
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Two independent current sources with one opamp?

simulate this circuit – Schematic created using CircuitLab The above circuit delivers a predetermined current to the load: $$i_L=-\frac{u_s}{2R}$$ Is it possible to extend it, so that it does ...
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What is causing the DC Offset in Mirrored Howland Current Pump Circuit

I am creating a current source to try to expand my knowledge about electronics design. After some research I decided to build the Howland setup since I want to develop a bipolar current source. The ...
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dependent current source polarity

In this question, I apply the current cycle law, I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here. ...
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op amp - current source - voltage output

I have the electronic schematic bellow composed with two op amp and I want to determine the voltage output of the X2 op Amp. I m a little bit confusing about the aim of using the zener diode D1 in ...
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Why is the voltage drop created by a current source added?

A few days ago a similar question was asked for the simple circuit below consisting of three elements in series (voltage source, resistor and current source). Despite professional explanations, the OP ...
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Underdamped RLC with CCCS, calculating capacitor voltage

Referring to "Electrical Circuits" Nilsson/Riedel 10th Edition. I have a classic underdamped RLC circuit with a CCCS (Current Controlled Current Source) with a current multiplication factor ...
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[op amp - Gain current source - current reference]

I have a question about the formula to consider for calculation of the gain for the electronic bellow. Thanks for your support.
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op amps comparator or differential amplifier

I have a part of electronic schematic as described bellow, I'm a little bit confusing about the function of the LM321 amplifier. In this case, can we say that is a differential amplifier or just a ...
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Need help for pointing out, source follower circuit with current source, designing NMOS

I'm not sure did I solve this problem right. I made \$ r_{o2} \$ , which is resistance looking at Q2 drain. So I can get $$ g_{m,Q3} = 1.8m(A/V) $$ from $$A_v = \frac{r_{o2} || r_{o3}}{1/g_m + (r_{o2} ...
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LM317LM as a current source

I have been using LM317L as a current source for generating 2-50mA current for a load, by following the datasheet, P14: So far so good, but now I have come across LM31L-n, particularly LM317LM/NOPB, ...
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Opamp input bias current and current sources

I have a current source connected to a load and I want to measure the voltage at the output of the source, and therefore I would like to buffer this voltage. In this configuration, I am under the ...
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Circuit for OpAmp-MOSFET based constant current source for 0.2 - 1.5A

I'm a beginner in electronic circuit design and have designed my first Voltage based constant current source using OpAmp driven MOSFET (based on this). The intended current output needs to be ...
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JFET Constant Current Source (CRD alternative)

Today I have build constant current source based on J111. To drain I connected VCC it's 24VDC from laboratory power supply, then I connected resitor 470Ohm between gate and source. To source pin i ...
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PMOS and NMOS Current loads in Common Source Stage

I am new to the concept of Single Stage amplifiers design using CMOS. In that, I came across a concept of using current source as loads in design of Common Source Stage, where it was mentioned in a ...
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Fixed current source

Thank you for reading this question and forgive me if I sound naive. I am working with a device that uses 4-20mA as set-point, I need 3 fixed values to work with this device: (4mA, 12mA, 20mA) The ...
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Measuring current output of a diode driver

I have a laser diode driver chip that can produce DC currents up to 200mA. The current is adjusted by a potentiometer on the driver chip. The driver chip has four pins: inputs: GND, SUPPLY outputs: ...
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Constant current source with MOSFETs

I have a question regarding this constant current source circuit: I have seen this circuit with two BJTs (like in the figure), but sometimes T2 is a MOSFET (I assume for lower Rdson resistance and ...
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Meaning of “A voltage source “likes” an open-circuit load”

I read a book "The Art of Electronics" by Paul Horowitz, Winfield Hill. In the book, I saw some phases. A voltage source “likes” an open-circuit load and “hates” a short-circuit load A current ...
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What are some practical examples of a constant current source?

Please don't state the obvious that nothing is a perfect constant current source. And please do not give examples of how to create them from components. I looked at this SE Q/A which stated the ...
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Efficient current drive with arbitrary waveform

I need to drive a defined, arbitrary current waveform into an output with a load impedance that may not be constant. Currently, I am using this: The 100V is created from 9V dc using a standard boost ...
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Oscillations in voltage-controlled current source with MOSFETs and opamp feedback — Why?

I have a circuit that should operate as a voltage-controlled push-pull current driver, able to source or sink at least 2A (into a 1 ohm load). It has unexpected oscillations on the output current. ...
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4mA-20mA loop behaviour when out of range

I have a temperature sensor that records temperatures from 10ºC to 30ºC, but in my project they only want temperatures to be read in the range of 15-25 with 4ma when 15 and 20ma when 25.My problem is ...
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Mesh current method problem with voltage controlled current source

I'm signed up recently to this site but i need help for my Fundametal of Electrical Engineering course.I need to find power of the current source. Thank you. Note: (y is equal to 2)
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first order circuits

I solved this circuit for the current in the 3 ohm resistor and I thought that the current would be continuous but it's not. The circuit is first at stable state, then we turn the switch off and the ...
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How to calculate using mesh method when there's a current source and a resistor between two meshes

I'm trying to get the current in the 3 ohm resistor using mesh analysis. Forget about thevenin's theorem here. However, what I know is that if there's a current source between two meshes then we do ...
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How to sink more current than specified?

I am using the TLC5940 (datasheet) in an upcoming project to control the cathode side of an LED matrix, but each of my LEDs needs ...
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The solution for current

I am trying to solve this problem but I failed to solve it. Please can someone solve it for me?
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circuit analysis transient response in an RC circuit

I asked this question already yesterday, but it seems like I didn't explain it well enough so I will give it one more go. This circuit is powered by a DC current source. I am trying to find out how ...
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Trouble understanding how dependent current sources affect a circuit (Two-port networks)

While reviewing a problem from my recent test on two-port networks I noticed that it made its way online. When someone was explaining the solution they utilized a point that I just completely missed. ...
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Using Thévenin's Theorem / Voltage Across Independent Current Sources

I've been attempting this problem regarding the usage of Thévenin's Theorem to find the value of Io. I am able to get the correct Thevenin Resistance, however attempting to find the Thevenin Voltage ...
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Circuit with dependent source confusion

Can we find the value of \$i'\$ in this circuit, considering \$I\$ and \$R\$ are known? Using Kirchhoff’s Current Law we have that \$I = i + i'\$. If the dependent source voltage was \$ki \;, \; k \...
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Help refining a current control loop circuit

As a follow up to this question. (Sorry if this linking other posts is wrong. I'm new to forums) Will this design for an XHP70.2 LED Driver with arduino control work to the params specified? TL;DR: ...
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Will this design for an XHP70.2 LED Driver with arduino control work to the params specified?

I am making a driver PCB to drive an XHP70.2 LED at 15A (~7v) Continuous, Controlled from an Arduino. I am new to OpAmp's so I would like to know: Does this circuit look as though it would function ...
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How does adding a current source and extra resistor to source follower improve its performance?

This question is similar to FET - Source follower utilizing current source to lower voltage offset, although I do not entirely understand the explanations, which is why I am posting my own question. ...
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Cascode current mirror output dynamic range

let's consider this cascode current mirror (Microelectronic Circuits, by Sedra Smith): The books says its best advantage is the high output resistances, which is amplified by the presence of Q3. ...
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How to do i solve this electrical circuit? [closed]

I've been trying to solve this circuit with two current sources: Following is given: ia = 1mA, ib = 2mA R1 = 1K, R2 = 0.5K, R3 = 2.2K, R = 4.7K Personally I've been trying to use KCL to determine ...
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What is the idea behind the ingenious Widlar current limiter?

For a long time, I had the idea of this circuit as a short circuit protection. I first saw it in the output stages of the Widlar's 301 and Fullagar's 741 op-amps... and knew it was Widlar's invention. ...
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Current source with such low noise even possible?

I am thinking about how or if it is even possible to build a particularly low-noise voltage-controlled DC current source. I need currents of up to 1.7 A (DC) while keeping its output noise below 1.7 ...
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Why can capacitor act as voltage source and inductor as current source?

Why can capacitor act as voltage source and inductor as current source?don't explain this with a math formula,just use an easier method,thanks a lot!
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Differential amplifier with a current source

How to change the current source in the emitter here, so that the whole thing can be biased from a positive power supply (without the need for negative rail Vee) keeping all the other parameters more ...
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123 views

Why can we see the current source as a open circuit and voltage source as a close circuit?

What is the \$R_L\$ value can maximize the power of \$R_L\$? simulate this circuit – Schematic created using CircuitLab The solution: simulate this circuit \$R_{th}=1+2+1=4\$,so when \$R_{L}=...
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current mismatch PMOS (current mirror)

I am designing a PTAT (proportional-to-absolute-temperature) current generator with 2 PMOS transistors for a bandgap circuit. In which way does the aspect ratio of a MOS transistor (M1 and M2) ...
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SIPMOS as current source

I read this question and I have the same issue: acquire and protect an input with 5-24V range. I wonder if nowadays I can use a BSS126 as current source transistor. It's a depletion mode N-channel, I ...
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Is a current source a single component or the same as a voltage source?

Is a current source a component on its own or is it the same as a cell? If the two are different why does the current source supply only current and a cell supply both current and voltage?
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How do we create current sources?

Constant current sources (simply, current sources) are useful and necessary devices. They are widely used to drive LEDs, charge capacitors and batteries, to bias differential amplifiers, etc. The only ...

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