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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2answers
63 views

30V adjustable current LED driver

I've recently started a project that has some pretty loose specifications. I need to develop an LED driver that can take an input of somewhere between 7.2 and 24V, and drive an LED panel at 30V with a ...
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2answers
44 views

Combining a benchtop power supplies

So I made an error when purchasing a power supply that was far below desired voltage (dc). The power supply I bought certainly produced enough current, however, and I am wondering if it is possible to ...
3
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3answers
89 views

Unstable Feedback in Opamp+MOSFET circuit for Voltage Controlled Current Source

I'm attempting to build a 1 Amp LASER driver that can be pulsed (at ~10kHz) and gives control over current with a voltage (from a DAC, for example). I'd like to scale it up to 10 Amp pulses ...
3
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0answers
49 views

MOSFET Drain, Source and Bulk connected to a source

Background: I have a circuit for a FGMOS and they are describing the Fowler-Nordheim Tunneling (FNT) mechanism. The picture features two transistors: the main (FG)MOS and a secondary MOS to ...
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44 views

Proteus Sine Current Source Simulation Issue

The circuit below is being simulated in proteus isis v7 Current Source has Amplitude value 5A (as asked by Proteus). Two Resistors of values 3 ohm each and then there are two AC voltmeters ...
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1answer
35 views

Different time constants for charging and discharging of a circuit with a constant current source and a capacitor

Consider a circuit that only has a constant current source and a capacitor. The voltage across a capacitor is proportional to the integral of the current I, times time. Since the current is constant ...
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2answers
74 views

Does a constant current source add to existing current?

If I have a circuit where one branch contains a constant current source (e.g. 2A), does the current leading out of the current source equal the current leading into it (e.g. 4A) plus the current of ...
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28 views

Ac current amplifier with pwm current control

I'm starting to build a piece of test equipment to test a trip device for switch gear breakers. I need to amplify an Ac current source. When the breaker is in service the trip device receives it's ...
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1answer
31 views

How to get constant current across varying Rload in h bridge

My I is a constant source of 10 mA from Vsupply of 50V, so my Rload can max at 5k at 10mA. I load is going both directions. My Isource is constant, but Iload is changing with varying Rload, why is ...
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2answers
83 views

voltage current converter by op amp circuit

I am trying to convert 5V to a constant current source for op amp I use AD822. for 250 ohm I use 180 ohm, so I should get a current of 28 mA. I verified when Rload = 0, 28 mA across negative ...
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2answers
120 views

Are op amp and voltage current converter same

I am trying to create a constant current output for my project between 0 - 10 mA. I read we can convert voltage to current by using op amp ...
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1answer
66 views

DC voltage source connected to an inductor is a current source?

I was reading about voltage boost converter, where the DC voltage source in series with the inductor is mentioned as a current source. Why is this? Also, an inductor in series with a load resistor is ...
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1answer
27 views

Curret mirror with discrete BJTs?

I need to supply power for some power diodes. The power supply units are current regulated, the diodes are connected in series. Let's say that i hve 3 strips of leds, each one needs 400mA, around 20V ...
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0answers
5 views

sources in Vector wave equation for FEM

I am studying the FEM for vector wave equation from Maxwell's equation. I have some questions and ask for help. The vector wave equation for electric field can be read as $$\nabla \times \left( ...
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1answer
203 views

Convert AC/DC power supply to current source for battery charging

I have an AC/DC power supply unit (400W) with the controlled output voltage (40V...60V). It would be great to use such a power supply as a current source to implement a dual step current changer. The ...
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2answers
182 views

How does Stitching capacitor provide shortest return current path between plane splits, as we know that it blocks DC current?

I heard that Stitching capacitors are used to provide shortest return path whenever a signal is routed along the 2 power plane splits. As we know the return current path will be right under the trace. ...
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2answers
107 views

Current source as load in a differential amplifier

In Design of Analog CMOS integrated circuits by Razavi I found the following differential pair design. It uses a MOS as load and it acts as a current source. My question is how should you bias the ...
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1answer
62 views

Voltage Output of a Current Source in Parallel and in Series with a resistor

Hi All, I imagine this is a pretty basic question to ask but I'm struggling to get my head around this. I'm trying to find \$V_{out}\$ of the circuit above. Now I understand why \$V_{out}\$ can be ...
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1answer
62 views

Two opposing voltage source, of different current capacities?

If two voltage source of the same value(20V) are wired in series and they both have different current capacities, could there be any current flow assuming the resistance(internal & circuit) are ...
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1answer
51 views

Help solving a 2nd-order RLC circuit

This is the practice problem 8.9 of Fundamentals of Electric Circuits 5th Edition. Can someone help me with this question? I need a more detailed solution of this problem. Especially, what are the ...
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1answer
39 views

Limits to transistor current source / mirror?

Are there any low end limits to how low of a constant current you can make with a transistor ? For a simple circuit like the following, is there a lower limit to the achievable constant current ? ...
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3answers
87 views

Current Limiter, can someone troubleshoot this circuit?

so I am trying to limit the current output with x2 3904 transistors and a sensing resistor. This is currently what I have, but am not sure why it doesn't work. That current supply is going to be a ...
0
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2answers
114 views

Driving proportional valves from microcontroller

I am looking to drive a current regulated proportional (solenoid) valve that needs up to 85mA @ 24V from a microcontroller. So far I found this circuit that looks pretty straightforward: What are ...
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1answer
76 views

Driving a low current solenoid with a low voltage H-Bridge

I'm trying to drive a solenoid to create a magnetic field. I've got a constant current controller circuit that supplies the current I need, but I'd like to control this using an H-Bridge so the the ...
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1answer
82 views

Alternatives for a UDN2981A

I'm making the circuit depicted here. I already have the shift registers I require, but I can't find any UDN2981A ICs in the stores I have available to me. Unfortunately, I don't have time to wait ...
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1answer
112 views

Voltage step up for bidirectional current source

I will be using a circuit similar to the following to create a bidirectional current source driving a max load resistance of 10k at a max of 2.5 mA. (based on this article ...
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1answer
124 views

current control via microcontroller

I have a micro-controller which calculates and decides about the current each minute. Then for one minute the circuit must hold that current constant. Then it should control the current via a buck ...
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3answers
405 views

PSU Current on negative line

While i am quite familiar with most of the specifications on a power supply unit like this one, I fail to understand what is going on with the negative voltages. I have a few theories, though. ...
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0answers
58 views

Distributing 3A source to components

I have a 3A power source and need to distribute this to: Raspberry Pi 3 sensors LED Stepper Motors I understand the breadboards are rated for a max 1A. Does anyone know how I can use all 3A in my ...
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1answer
149 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
199 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
152 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
45 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
2k 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
121 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
160 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 ...
0
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1answer
55 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 ...
3
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3answers
571 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 ...
0
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0answers
25 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. ...
2
votes
3answers
97 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 ...
0
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1answer
74 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
86 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 ...
1
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1answer
101 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
362 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 ...
1
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1answer
87 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
62 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
355 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
241 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
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5answers
140 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 ...
0
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1answer
37 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 ...