Tagged Questions

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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1answer
20 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 ...
0
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0answers
69 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
42 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
104 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
73 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 ...
5
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5answers
730 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 ...
0
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2answers
82 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 ...
1
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1answer
120 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 ...
0
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1answer
56 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 ...
1
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1answer
85 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 ...
0
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2answers
80 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
votes
2answers
114 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 ...
1
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1answer
73 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 ...
1
vote
2answers
123 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 ...
0
votes
1answer
104 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 ...
0
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3answers
147 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 ...
0
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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 ...
2
votes
2answers
162 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
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3answers
166 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 ...
0
votes
1answer
89 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 ...
1
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2answers
160 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, ...
0
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3answers
129 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 ...
4
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3answers
127 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
129 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\$ ...
1
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2answers
128 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 ...
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2answers
46 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 ...
5
votes
2answers
216 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 ...
1
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2answers
99 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
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1answer
169 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 ...
3
votes
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 ...
0
votes
1answer
44 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
votes
1answer
181 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 ...
1
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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
64 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
51 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
373 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 ? ...
0
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1answer
58 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. ...
0
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2answers
91 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 ...
0
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1answer
69 views

How do you find the equivalent voltage of the current source in this circuit? [duplicate]

The circuit is shown at this schematic. How do I find the equivalent voltage of the current source by simplifying the circuit?
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2answers
110 views

Equivalent circuit?

Can I simplify this circuit to just one resistor? How can I find the equivalent voltage of the current source in this circuit?
2
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1answer
191 views

Understanding 74LVC245 datasheet and current source/sink

I'm using a SN74LVC245A (datasheet) to shift 5V TTL down to 3.3V so I can read the signals with a Raspberry Pi. However I am getting really weird results (a 60Hz input signal is picked up by the Pi ...
3
votes
3answers
337 views

Maintaining a constant current with varying loads

I've designed a constant current source using a current mirror, we need an output of about 50mA. The problem is that we build it and heat has become a problem.The transistors and the R_load are both ...
2
votes
2answers
208 views

Howland Current Pump VS Wilson Current Mirror

I am interested on knowing what would be a better solution to create a current source for low current applications (below 20mA), an opamp based current source such as a Howland current pump (link to ...
8
votes
4answers
3k views

Choosing resistor values for non-inverting amplifier and why?

The gain here is A = -Rf/Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why? I know that you could have infinite number of combinations for these ...
1
vote
1answer
139 views

How can I model a variable current sink in spice?

For a project I am working on (related question here) I need to model a nonideal variable current sink in spice. Simply reversing the orientation of a current source or inverting its value is not ...
1
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1answer
69 views

How do I increase (multiply) the value of a current sink?

I have been shown an IC that is a current sink PWM dimmable LED regulator. It happens to be a WS2811. While this works well for low drive currents (up to about 20mA), I was approached with the idea of ...
1
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3answers
920 views

Constant Current Source circuit improvisation

simulate this circuit – Schematic created using CircuitLab I was wondering whether I could use this circuit as a constant current source provided my load circuit impedance was less than ...
2
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3answers
466 views

How to make a constant current source

I don't understand current sources! Batteries are voltage sources, but how does one actually implement a current source? I was looking at current mirrors to see how they work, and I understand the ...