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 ...

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191 views

Programmable current sink

I need a current sink that I can control from a micro-controller. Should handle 5V up to 4mA or so in at least 256 steps (more is better). I'm looking for a design, not so much a complete product, due ...
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1answer
85 views

Why feedback is activating at more than 4V?

In this circuit: I don't get why the current start flowing from more than 4V. I thought was due to threshold, but the same happens with an NPN as M2 or using an BS170. With this last one, ...
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0answers
41 views

Is this source transformation allowed?

I am trying to understand source transformations in AC circuits. From my understanding, one can simply find the impedance of inductors and capacitors according to: $$\text{inductors: } Z = j \omega ...
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2answers
115 views

Operational amplifier used as a current source

As a laboratory task at my practical engineering school we were asked to make the simple circuit shown below, prove that it acts as a constant current source regardless of its load, and answer some ...
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2answers
101 views

Opamp Misbehaving in Constant Current Source Circuit

I'm planning to build a current regulator for a power supply and I'm prototyping a number of different regulator circuits. First up, the op amp and transistor circuit shown below. I felt I ...
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5answers
117 views

Why this current regulator won't regulates?

I'm trying to make a current regulator to power up some LEDs. For now I'm working only on PSpice models. The circuit above works well if the sensing opamp is configured as voltage follower or even ...
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1answer
21 views

Trying to make a current source with an XRP29302 (linear regulator)

I'm familiar with the configuration to make an LM317 (voltage regulator) into a current source. You connect a resistor between the Vout and Adj pins (Say 1.24 ohms) and draw the output directly from ...
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1answer
59 views

0-5V Voltage controlled Constant Current Source with High & Low current Offset

I am trying to design a MOSFET constant current generator controlled by a 0 - 5VDC signal (non pwm). I have had no problems getting a nice resistor divider and an op amp to control the circuit. I am ...
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2answers
75 views

Replacing resistors with active load in active filter

I am building a low pass filter IC in 0.25 micron CMOS. My design requires 14 Mega-Ohm resistors. I want to replace them with an active load in order to save space. If possible I would like to use a ...
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3answers
294 views

what is this current source

When we connect a resistor to current source a finite amount of current flows through it right? Okay but how is a closed path complete?I mean the current source has infinite resistance(I'm talking ...
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1answer
31 views

CCVS (current controlled voltage source) in practice

In my current project I'll possibly need to deploy a CCVS (Current controlled voltage source). It is transconductance amplifier or converter and many manufacturers offers transconductance amplifier ...
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2answers
124 views

Capacitors not keeping charge as expected

I have a voltage doubler charge pump that is used to provide voltage over an IR LED for a short pulse, I also have a driver circuit for the LED to sink the right amount of current that I am requiring. ...
2
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2answers
53 views

why does the parallel resistors with voltage source can be ignored as well as resistors in series with current source in term of equivalent circuit?

I have a problem dealing with equivalent circuit. I don't know why when the resistors that is parallel with the voltage source can be ignore as well as one in series with current source. Of course the ...
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3answers
107 views

Driving 48 LEDs with 1 Single Current Source

I need to drive 48 UV LEDs for UV paint curing system. (LED: 3.5V, 20mA) I found a simple current source, modified it, set the current to 20mA. The voltage on 3 leds is 10.50V (3 x 3.5V, exactly what ...
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0answers
31 views

Power Supply Requirements [duplicate]

I am building some prototypes for my thesis but I am not sure how to buy the power source for them. I need to how to choose a proper power source(Volts, Amps, etc). The number of motors will vary but ...
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1answer
75 views

Hooking up two voltage regulators for more power?

I have two LM317's, which I am wiring up as a current source for two high power, 10 watt LED's. The 317 can operate @ 1.5 amps maximum, so I plan to build two of these circuits. The problem I am ...
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5answers
849 views

How does this constant current sink actually work?

So I have implemented a constant current source and it works wonderfully, but I was just hoping to try and understand it a little bit more! Here is the circuit in question: I have tried doing some ...
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2answers
87 views

Ohm's Law of a circuit which have both Voltage Source and Current Source

The Voltage Source have a specific voltage through it regardless of the circuit's current and its resistance while the Current Source have a specifice current through it regardless of the voltage ...
2
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1answer
180 views

Calculating the Output Resistance of a Widlar Current Source

I'm currently struggling to understand the small signal equivalent used in the following calculation: http://en.wikipedia.org/wiki/Widlar_current_source#Output_impedance My problem is: How come they ...
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1answer
61 views

Understanding CT sensors and current to voltage circuits

I have difficulties to wrap my head around the concept of CT sensors (SCT-013-000 f.e.). I currently want to improve the current to voltage circuit I use with the usage of an op amp. While I can just ...
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1answer
92 views

Nodal Analysis of a circuit with a dependent source

simulate this circuit – Schematic created using CircuitLab Hi, So the trouble I am having with this problem is that I don't know how to do nodal analysis with the dependent source. I ...
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2answers
89 views

Kirchhoff's loop equation when there's a current source in it?

This is driving me nuts and I couldn't find a solid awnser. How do you get the loop equation (using Kirchhoff's 2nd law) if there's a current source in it? I mean.. does the voltage after the current ...
2
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2answers
135 views

lm317 current source sense resistor

Why is sense the resistor swapped with the load resistor here and how does this circuit work? From my understanding of circuit output (node at LED anode) will be at constant 1.25V, and it will ...
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1answer
74 views

What is the current gain of this op-amp circuit?

I just happened to see this circuit in some lecture slides and I thought I could solve it. Unfortunately, I've been trying to check my result with an ideal simulation in LTspice and all my attempts ...
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2answers
142 views

Zener Diode Current Source

How would I make a Zener diode current source? Something like this? I don't know how to figure out what resistors/transistors/diodes I need. I guess what I'm asking is, how do I calculate what ...
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1answer
112 views

How to eliminate early effect in constant current source

When designing an differential amplifier it is important to have a precise constant current source (which I will abbreviate with CCS). It helps to keep out signal injections from the supply rails. A ...
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3answers
185 views

Current flow through a battery

So this might be a stupid question and I really should know the answer to it but I am having difficulties with a circuit I have made to drain a battery. The basic idea of this circuit is that I have ...
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1answer
38 views

Current Injection Via Jumper Design Help

I am currently designing a circuit that uses a 5V 2A power brick. The circuit requires a current source and I have seen good efficiency with Ohm's Law. The current is variable through a 2k ...
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2answers
179 views

Sourcing current with sink LED driver

I'm using an existing keypad with 8 LEDs that source power. I was hoping to use and LED driver of sorts, but all of the ones I find only refer to sinking power. Is it possible to use these drivers to ...
2
votes
3answers
207 views

How do I keep my constant current source constant?

So I am trying to created a current source that will be used to drain a battery at specific time intervals for a specified duration. simulate this circuit – Schematic created using ...
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1answer
99 views

Combine two signals of different frequencies in a test setup

I have a device that is powered from a current source. The current source supplies 10A at 60Hz - the magnitude is roughly 5-10VPP. I would like to inject another signal on top of that to simulate ...
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2answers
176 views

Parameters for voltage-controlled current source

I'm trying to implement the following circuit in a project: VCC coming in is 18v. The op-amp is supplied with 3.3v. There is a waveform voltage input from 0-2 v that can oscillate at up to 100hz, ...
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3answers
139 views

how to create a high current source?

I'm looking to observe magnetizing offsets of various current sensors. The idea is that when you pass a high current pulse (close to the rating of the device) through a current sensor and then return ...
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votes
3answers
133 views

Current source for milliohm loads?

I've been working on a model maglev train as my Grand Hobby Project; something around the H0 scale. The initial idea was to use the Inductrack mechanism to keep it simple. To summarize, a Halbach ...
2
votes
1answer
138 views

Current source improves linearity on collector BJT

I'm learning about analog electronics. I'm looking into amplification stages at the moment. Question 1: Single BJT C-E Amplifier. Usually you put a resistor between collector and V++, so as \$I_b\$ ...
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2answers
153 views

Current controller circuit to drive solenoid bank

I am working on building a current controller circuit used to drive 8 solenoids (for those interested, the solenoids produce magnetic fields for use in a Zeeman Slower). My problem is that there is ...
12
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3answers
1k views

Do constant current batteries exist?

Do constant current batteries exist? If not, why not? Else, why are they not very common in the market? I am not talking about an ideal current source. But it should be a constant current source for ...
0
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2answers
47 views

Total current in two circuits - two methods

I have two norton's theorem questions and I am confused about the two solutions. In the first one below, the current can be found by simply subtracting one current from another. (I believe this is ...
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2answers
267 views

Standard current and discharge current

I've been looking into batterie's datasheets and don't understard what 2 of the specifications mean: continuous standard current and maximum continuous discharge current. Could someone explain this to ...
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3answers
126 views

Current source - Achieving a defined settling time with variable load resistance

I'm trying to build a voltage-controlled current source which is supposed to work with a wide range of load resistances. Currently the plan is to use an NPN transisitor as voltage follower to do the ...
1
vote
1answer
183 views

Nodal analysis independent and dependent voltage source and current source

After spending quite a few hours I am stumped with this problem while trying to solve for Vo, which is supposed to 0.5V and this was confirmed through PSpice. I have no idea what I am doing wrong or ...
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2answers
1k views

Superposition principle: Dependent sources treated as independent sources

Since I began studying, I was taught that when analysing a circuit using multiple sources, independent sources could be turned off, meaning that I could transform a voltage source into a short, and a ...
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1answer
48 views

Find four current mesh

I have to find the 4 current mesh in this circuit V1= 12V R1= 1/12Ω R2= 1Ω R3= 1/3Ω I1= 6A R4= 1/3Ω R5= 1/2Ω R6= 1/13Ω I2= 6A I tried a source transformation and got this I3= 144V R1-2= ...
2
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1answer
197 views

Current Controlled Output Using PWM

I am looking to control a proportional valve with a PWM signal that will correlate into exact current amounts (for example a 25% duty cycle will output 200mA, and a 90% duty cycle will produce let's ...
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1answer
49 views

Cadence, BSIM3V3, and the Body Effect

I am trying to meet the compliance/min output voltage of a wide swing current mirror so the output current (10uA) is within .1% or +/- .01uA. I am using Cadence and ami06 nFET's to do so. I am always ...
2
votes
1answer
72 views

Special Source Transformations

I'm not sure if this was asked already, but I could not find it when I searched. We're learning about source transformations, and while reading my textbook I came across this: and in the following ...
0
votes
1answer
52 views

What Formality Am I Using To Isolate This Portion Of The Circuit?

If I have this circuit in which the switch opens at t = 0 (after being closed for an infinite time, making the circuit steady state), for which I'm trying to find the voltage across R2 as a function ...
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6answers
385 views

Is there any physical device called current source?

I have seen both current source and voltage source in many electrical circuits (in paper). When it comes real hardware battery can be considered as a voltage source. Then what is a current source ? ...
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1answer
60 views

Which options exist for switching the polarity of an output with low leakage?

In my application, I want to switch the polarity of an output which supplies a controlled current up to 50mA (accuracy 100uA + 1%) at up to 36V. The current sensor is on the low side of the output. ...
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2answers
92 views

Switching current source ~1 μA — how to switch off quickly?

I would like to have a precision current source ~1 μA loaded by a resistor ~100k and a voltage source. Also I would like to switch on and off the current. The problem is that when the transistor ...