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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35 views

Modifying LM334 reference schematic to 100uA/500mV

I'm trying to understand how to modify the circuit below to provide a 100uA constant current drain and 500mV Vds for an ISFET. Based on the help so far, this is the schematic I've come up with:
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2answers
49 views

Differences between current sources transistor and current mirror

In this configuration simulate this circuit – Schematic created using CircuitLab if the two pMOS are equal, they provide the same drain current to both the branches: suppose that Vbias ...
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1answer
48 views

Power ATMEL ATMEGA328P directly from USB

im wondering if it is Ok to power an ATMEGA328P directly from an USB-Poweroutlet i.e. an Apple-USB-Charger. And I mean directy: VCC to Pin 7+20 GND to Pin 8+22 Peripherals should be powered from this ...
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2answers
41 views

What would be the voltage across a load at a junction point where two current sources are connected in series?

If two current sources are connected in series,then what would be the voltage at their junction point across a load?
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7answers
1k views

What's the point of a current source?

simulate this circuit – Schematic created using CircuitLab OK. So I've been told that the current flowing into the current source (that is, into the arrow's behind) is the same as the ...
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0answers
42 views

Oscillations in Master-Slave High Current Source

I am attempting to trouble shoot a circuit and I am a bit stumped. The circuit is high current source (10-20A) based on a master-slave configuration using OPA549 high power op-amps. There is one ...
3
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1answer
109 views

Does this current buffer analysis make sense?

I've transformed this circuit: simulate this circuit – Schematic created using CircuitLab In this one: I am aware that the input is V_in and the output is the current which enters in ...
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1answer
52 views

Current division and power delivery to resistors

I am trying to get the resistor e in this circuit to consume the most power possible by changing its resistance. It seems 100 ohms is just about right, a little less or more and it's power consumption ...
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3answers
391 views

How do I build a 10uA current source/limiter?

I need a constant current of 10uA through a variable resistor in the 100k values. I need to inject the current into that resistor and I need the resistor to be connected to Ground such that I can ...
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0answers
22 views

Biasing an SPD with a current source

While looking for an approapriate way to bias an APD (a SPAD), I've been suggested to use a simple constant current source (by means of a depletion MOSFET and a resistor) instead of voltage regulator. ...
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votes
3answers
88 views

why isn't Norton transform applicable on ideal sources?

An ideal voltage source has no resistance in series to it, so the it's transform the current source must have zero resistance in parallel to it. This means that all the current passes through the ...
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1answer
65 views

interference proof voltage regulated current source

I want to dim some LEDs, using the PWM output from a microcontroller. There are some more LEDs than in the schematic, already wired, so that they need nearly 12 V to give maximum light at about 50 mA. ...
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1answer
51 views

Source with variable output impedance / Fast large signal voltage variable resistor

I need a source that has an adjustable output impedance. Corner parameters are: Voltage range: +-5V, large signal BW > 10 MHz, output impedance range at least 1k to 500M. Larger would be better. A ...
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1answer
73 views

Facing to real world feedback designs (here, Constant Current Generator)

I still work on a current generator made with 2 opamps and a nMOS. If I find the bias point to understand how much my LED can be driven, I still have problems to find an affordable way to derive the ...
2
votes
2answers
257 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
47 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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1answer
156 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
141 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 ...
2
votes
5answers
127 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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votes
1answer
27 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
161 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 ...
2
votes
2answers
98 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
335 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
54 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
129 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
106 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
143 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
32 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
76 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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votes
5answers
1k 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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votes
2answers
102 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
votes
1answer
220 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
votes
1answer
83 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
115 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
139 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
185 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
vote
1answer
81 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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vote
2answers
224 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
133 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
votes
3answers
409 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
votes
1answer
41 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
216 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
283 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
137 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
219 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
152 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
votes
3answers
142 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
175 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
229 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 ...