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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35 views

Why nMOS transistors use 'Head' current source and pMOS transistors use 'Tail' current source as their load?

Here I am taking an example of common source configuration(refer figure). Generally head current source is used as load with nMOS and tail cuurent source with pMOS. Why can't be this other way around? ...
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67 views

Current Source and Current Sink

Excuse me for this simple question. Can someone tell me how this circuit works? In the video, it is said that, the voltage drop across the resistor connected to NPN/PNP will be only a diode drop. ...
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52 views

Is this polygon pour, how much current can it carry?

On my attached picture, I draw battery pins, (red square) component that want to current, (blue square, a component want to about 4-6 ampere) and way of current (black line). I have a some questions. ...
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When to use P-Type current source(using pMOS) and when to use N-type current Source(nMOS)?

I am referring to Prof. Behzad Razavi Lecture https://www.youtube.com/watch?v=GAvZLyii3aw&list=PLiDoPUX9nLkIw9EnIv_3K19wlcyJ6msYd&index=2 (Minutes 19-26) Prof. says to use nMOS when we draw ...
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32 views

Understanding current sourcing and sinking in TL2426 rail splitter

I have a 40dB active bandpass filter being powered off a single rail power supply with the TL2426 providing a virtual ground so I can get a dual power supply configuration. Currently, I'm having ...
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49 views

Proper voltages from same source

I'm building a small electromobile. I was planning on using a car alternator as the motor, however I'm now looking into buying a 48V 500W BLDC motor. The problem is I'm not really sure how to manage ...
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49 views

Stable current source with discrete components

The purpose of this is to compare and learn different circuit topologies, not use of the shelf solutions which obviously provide cheaper, simpler and better results. Considering this requirement (no ...
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81 views

How should I make a constant AC current source to drive an electromagnet?

The inductance of the electromagnet is about 0.05H and the resistance is under 50 Ohm and I need about 2 to 5 Amperes to drive it. I need to be able to change the amplitude and also the frequency at ...
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43 views

Current limiter doesn't work

I've built simple current source with current limiter. Regulated part of the circuit is supplied by 10V from Lab Power Supply in which I set also current limit to some value. Idea is that U1 pushes ...
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105 views

Problem with MOSFET making my current dissapear

The current of 150 mA has to go around 18 different circuits, one at a time. Now I am trying to use 18 LDOs as suggested below. But now the problem is that the current that is supposed to be 150 mA ...
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30 views

Current source for discrete differential amplifier

I hope someone can point me to the right direction. Basically I face the same problem like the author of the following question. How do I choose the correct current for my differential amplifier? I ...
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273 views

Understanding a current source topology

I'm reading Douglas Self's Audio Amplifier Design, and there is a circuit presented with a current source I can't understand. The source would be the one formed by Q5, Q6 and Q7. If Q6 would be '...
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87 views

What is this Venn-Diagram-looking symbol?

So I am looking at the datasheet for the LTC4416, and there is this Venn-diagram symbol after the op-amp, but I don't think it is supposed to be an inverter. It is also used for these currents, but ...
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Idealized and simplified source with constant power supply

I have a multiport network in which I want to send an AC signal of constant average power, independent of the network's input impedance on the source side. While we would need matching networks and ...
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76 views

inductor resistor differential equation

I am trying to find the current through the inductor in this circuit. When I approach it, I get a differential equation that does not seem like something I've learned how to solve. Am I making a ...
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59 views

Oscillations on High Side Sensing Current Source

I designed a simple adjustable constant current source that uses high side sensing but I can't seem to figure out where the oscillations on my output are coming from. The circuit is shown in a picture ...
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67 views

Calculate Norton equivalent in a circuit with a voltage controlled voltage source

I'm trying to solve a problem related to dependant voltage sources. I need to provide two answers which either I can't obtain or don't understand why I have obtained it. What I have done This is a ...
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30 views

Which power supply choose for lineal actuators?

I have two actuators each of them with the following characteristics: 16 inch, 12v, load 750 N, travel speed 10mm / s, duty cycle 25% BUT Current Draw is not specified, and I have no access to the ...
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91 views

Why does my Current Regulative Diode not regulate current well?

I recently ordered several E153 CRDs from Semitec (data sheet here) to maintain a steady current to an LED (data sheet here). Mistakenly, I didn't read the "Dynamic Characteristics" portion of the ...
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32 views

How do I turn a function generator into a current controlled function generator?

I'm using a custom pulse generator with voltage controlled biphasic (both negative and positive voltage) pulse train output to stimulate a living tissue which is grounded on one side. I need to be ...
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21 views

Finding current of circuit in steady state

I am unsure if I did the KCL correctly. Also if I switched from rectangular to polar without mistakes. Excuse me if the work is a bit sloppy I am new to the polar and imaginary coordinates.
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48 views

Source Conversion: Combining series current sources

I have done 1.1 and gotten 9V and 3k Ohms for the equivalent source. I am trying to do 1.2 without first converting to voltage source and I come across this situation: How would I combine the two ...
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Producing Bi-Phasic Constant Current Pulse using L293 IC

I am trying to convert a current source output into the bi-phasic pulses. I thought maybe using L293 IC might help to change polarity of the currents. Here is the picture of design: as can be seen ...
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Removing Overshoots in constant-current bi-phasic pulse generator

I am designing a constant-current, bi-phasic pulse generator in a simulation study. I have attached the circuit and output current pulse. As it this picture shows, I have a +600 to -600 micro Ampere ...
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75 views

Single MOSFET current source (JFET like)

Is it possible to build MOSFET current source similar to JFET current source like this: simulate this circuit – Schematic created using CircuitLab With MOSFET it should be something like this: ...
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73 views

Working region of NPN BJT

I have come across the following circuit where a BJT works as switch when I apply 23 volts to base using a 100k resistor. A 3.2 mA constant current source is connected to the collector of the BJT ...
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49 views

Measuring variable resistance as voltage value

I would like to replace the microcontroller of an old gamepad with a Arduino/Teensy board. To do this, I need to connect all buttons and the output of the 4 potentiometers of the gamepad's joysticks ...
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31 views

Advantages of using a singular vs multiple power source?

I have a simple system of 4 components that I am trying to power and I was wondering what are some of the general advantages of using a single power source versus a multiple power source to power the ...
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33 views

adjustable voltage controlled current source with negative values

I have a MEMS mirror which can tilt based on the input current. The current can vary between -15mA to +15mA in order to change the angle of the mirror from -15 to +15 degree. Now, I need to have an ...
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46 views

How to optimise this dual (bidirectional/bipolar) opamp+BJT voltage controlled LED driver?

I'm working on a dual, voltage-controlled LED driver circuit, where one LED's brightness indicates positive voltages at the input, and the other LED indicates negative voltage. The purpose of the ...
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56 views

Correcting DC offset in op-amp based controlled current source

In an attempt to develop an automated potentiometer measuring device I have implemented the following op-amp based voltage controlled current source, controlled by the output of a DAC. The voltage ...
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57 views

Paralleling Multibit current DAC: Improving Accuracy by Averaging

No doubt that if I put in parallel n DACs, multibit (i.e. 16 bit) current output R2R ladder chips, I get n-times higher current at the summing node and the output impedance is also reduced by "n". ...
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93 views

Transistor current source \beta varies (AoE Ex. 2.23)

I am having trouble solving the following exercise: Exercise: If \$ \beta \$ varies from 50 to 100 for collector voltages within the output compliance range, how much will the output current vary? (...
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67 views

Topology choice for wide-output-voltage-range SMPS

I'm intending on building a off line (230VAC), 50W, isolated, constant-current switch mode power supply. This by itself is not a big challenge with the plethora of application notes and examples ...
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47 views

Variable Current Amplifier for Fan Control

I'm working on a project where I need to vary the current supplied to a DC fan. I am currently trying to use a BJT as a current amplifier to amplify a low current analog output (0 to 100 mA to vary ...
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68 views

Superposition with dependent sources

If the value of a dependent source (say CCCC) depend on the value of an independent source (say a current source). When setting the current source to 0, would that make the CCCC an open circuit (i.e. ...
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Turning off the LM3914 dot/bar display driver per the datasheet

I'm designing a circuit with an LM3914 dot/bar display driver and want to shut off the entire bank of LEDs based on conditions in the circuit. I'm having some difficulty turning off the driver from ...
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82 views

Thévenin's Theorem Example

I just started learning Thévenin's Theorem. My textbook gives the following example: I'm referring to online sources such as this to complete this problem. However, all of the circuit diagram ...
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37 views

Explanation of Source-Absorption Theorem Example

In the section on the Source-Absorption Theorem, my textbook has the following example: I was wondering: If the voltage $$v_\pi = - v_e,$$ then why do we get $$g_m v_\pi = g_m v_e$$ instead of $$g_m ...
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81 views

Variable Constant Current Supply

I've been looking around for a good CCS schematic, and decided to try making a simpler one even if it means it'll behave worse. I need a 12V (would come from an ATX power supply, more than enough ...
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37 views

AC Current Source - Modifiable Amplitude and Frequency

Just a heads up, I am not an electrical engineer. I need to build an AC current source of the following specifications. I have looked into IC chips, but none meet my specifications. I have started ...
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1answer
49 views

Current through a diode changes for the same forward voltage in two circuits

In LTspice IV, I am simulating a 1N914 diode behavior in response to a variable current source in two circuits. One circuit has just the current source and the diode, and the other has the current ...
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62 views

Resistive circuit analysis with dependent current and voltage source

The question in a study book says to find the current through R2. I have very little experience dealing with dependent current and voltage sources, so I get thrown off when performing loop current (...
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Figuring out the principal working of constant current source

I've the following circuit: simulate this circuit – Schematic created using CircuitLab I was told that this is a constant current source. I think that the resistors \$\text{R}_1\$ and \$\text{...
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135 views

LTSPICE Simple MOS-FET Stacked Current Mirror/Cascode saturation threshold less than expected

I am running a few very rudimentary cmos circuits in LTSPICE. For some reason, when designing stacked mirrors, I seem to get a much lower saturation turn on thresholds would be expected. I've tried ...
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376 views

Mosfet constant current

I am looking at a schematic that has a very similar form to a emitter follower but in the mosfet world. It's intended to keep the brightness relatively constant as the battery battery voltage ...
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1answer
185 views

Constant current source with shunt fet

I'm want to create a project with a LED strobe with IR LEDs. As LEDs the Osram SFH 4249-UV will be used in strings of 15 LEDs and 32 strings parallel. This results in a Vf of 34.5 - 45 V and a If of ...
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Find the current at the resistor

I've tried to divide current at 8A and then make a Kirchhoff voltage law between the resistor and dependent current source but I still can't solve it.
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272 views

Plot voltage for different resistor values in LTSpice

I've signed up for a SPICE course at work, that will take place on Monday and I'm desperately trying to learn electronics and SPICE. (I work as an embedded engineer but with very lacking electronics ...
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87 views

Led driver high current and voltage

For a project I have to design a led beacon that will consist of +400 LEDS. These LEDS will be driven only a short amount of time maximum of 3% duty cycle (frequency: 100Hz, pulse: 300us). The LEDS ...