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
54 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. ...
3
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2answers
35 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
40 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 ...
0
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1answer
46 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 ...
0
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1answer
33 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 ...
1
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1answer
34 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 ? ...
1
vote
3answers
71 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
votes
2answers
61 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 ...
0
votes
1answer
44 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 ...
0
votes
1answer
34 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 ...
1
vote
1answer
74 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 ...
1
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1answer
72 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 ...
4
votes
3answers
365 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. ...
0
votes
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 ...
0
votes
1answer
53 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
106 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 ...
0
votes
1answer
75 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 ...
1
vote
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?
11
votes
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 ...
1
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0answers
53 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
votes
1answer
127 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
votes
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 ...
3
votes
3answers
444 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
votes
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
90 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
votes
1answer
71 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. ...
0
votes
1answer
61 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
vote
1answer
82 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
294 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
vote
1answer
86 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, ...
1
vote
0answers
50 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 ...
0
votes
1answer
211 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 ...
1
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2answers
177 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
128 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
votes
1answer
30 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 ...
1
vote
1answer
244 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
106 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 ...
1
vote
3answers
356 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 ...
1
vote
1answer
70 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
votes
2answers
131 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
votes
2answers
169 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 ...
0
votes
3answers
151 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 ...
0
votes
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 ...
1
vote
1answer
78 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
votes
5answers
2k 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
votes
2answers
117 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
246 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
100 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
vote
1answer
130 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
votes
2answers
184 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 ...