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
27 views

Need help understanding the concept of “Circuit model of a discharging RL circuit”

I don't understand the statements for t<0 and t>0. Why does this happen?
3
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2answers
39 views

How to simulate a photo diode response

Currently my photo diode is exposed to pulsed laser with Pulse width : 10ns < tw < 150ns Pulse repetition rate : 1Hz < PRF < 70Khz Expected peak current : 50mA so when i ...
3
votes
3answers
100 views

Cheap, low-quality constant-current sink over wide voltage range

I'm looking for a cheap (as in: low component count, low PCB area, low component cost) way to put >= 1mA of load on a voltage that may be anything from 1.2 to 17 volts (minimum required load on a LDO ...
1
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1answer
76 views

RS485 current source/sink

I'm looking at using the RS485 to communicate between two Arduinos. I'm trying to wrap my head around the current requirements though... If I connect a driver to a receiver through a differential ...
1
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2answers
112 views

Battery discharge current

What is the meaning of standard discharge current mentioned on the datasheet of lithium batteries. Does it represent the maximum current load can take or it represent the instantaneous current ...
0
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0answers
43 views

Why is the dependent current source ignored?

I need to find i1 / v1 when i2 = 0. According to the solution manual, the KVL is -V1 = 2kOhms*i1 + 1kOhms(i1 + i2), and since i2 = 0 they get -V1 = 3000i2. Are they forgetting the dependent ...
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1answer
112 views

Are there any circuits to get output as a sum of a set of current sources?

I have 3 current sources (I1, I2 and I3) and I need to get an output of linear summation of the current of these sources. Iout = aI1+bI2+cI3 where a,b and c are gain factors (like 1 to 10 and are ...
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0answers
68 views

Is it possible to have a one way conductor?

Can you have a material such that, current can only flow in one direction, (or more accurately it is easier for negatively charged particles to move in one direction than another within the object, ...
0
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1answer
54 views

FET Current limiter 30A and overload detection

I plan to make a module for my motorbike to replace fuse by current limiters and overload detection system. I've heard nice things to do with J-FET. It should work up to 12V 30AMP. The detection ...
0
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1answer
87 views

Follower current source?

I need advice on a problem I'm having I need a follower to transmit an AC signal into a low impedance load which is the cathode of a triode but I also need it to be an adjustable current source to ...
0
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2answers
44 views

Current step generator - ideas for completing the implementation?

I'm working on a circuit that can act as a current sink or source. The goal is to control it using some digital means so it can output the required current. Right now I am not sure about the ...
2
votes
3answers
95 views

Is it OK to PWM a current source?

I want to control power RGB LEDs, for efficiency and safety they are better to be driven by a current source. I can use either linear or buck converters. I made a linear current source using ...
0
votes
1answer
36 views

How to connect multiple ACM 7135 to one ATtiny? [closed]

One ACM 7135 provides 350mA. Nine can fully power Cree XM-L2 U3. But that's 10W. ACM7135 only have Vin, Vout and GND pins. People are using them with ATtiny (example), apparently without any other ...
1
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1answer
81 views

Switching a ~10 μA current at ~10 kHz

I would like to inject 10 μA into my load, and to be able to switch the current on/off at up to 10 kHz. My first attempt is just based on the transistor current source in Horowitz/Hill. ...
0
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1answer
31 views

serially connected current source and resistor

In source conversion we can simplify circuit by shorting resistor in case of resistor and current source are serially connected and open resistor in case of voltage source and resistance are parallel ...
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2answers
142 views

simple adjustable current source for LED string

I want an simple adjustable current source that can drive a string of up to 9-10 LEDs at up to 350ma, with typical forward voltage of 2.85v, from a 30vdc power supply. I know there are off-the-shelf ...
0
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2answers
90 views

Current source with low-side LOAD

Why does this work? simulate this circuit – Schematic created using CircuitLab But this doesn't. simulate this circuit In the second schematic, V2 is adjustable. Is there a ...
0
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3answers
103 views

is there any way to get current from vibration?

I was wondering if you have something that vibrates , is there any way that you can make some power out of it?
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1answer
96 views

What is this circuit called? (Dual of a boost converter)

A boost converter is a circuit that uses power from a voltage source, to act as another voltage source with a greater voltage. To conserve power, it draws more current from the input than it provides ...
0
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1answer
56 views

Current Source Transformation

So my question is: Can I transform the current source I1 with R5 into a voltage source? I know for sure that if R3 was not in between them I could, but does it make a difference? I am not sure. ...
0
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1answer
71 views

Bipolar Voltage to Current Converter

I need a circuit or component which converts bipolar voltage to bipolar current. I have found the XTR111 from Texas Instruments and the 1B22 from Analog Devices. However, they only convert 0-10 V to ...
3
votes
2answers
90 views

PT1000 2 wire probe. Can I add third wire?

I'v got 2 wire (81 cm) PT1000 probe which I want to utilize in a project. I would like to use current source and couple of opamps to make the measurement through ADC (uC) just like described here: ...
0
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2answers
85 views

audio-taper potentiometer in 50-100 ohm range [closed]

Anyone know where to source an audio or logarithmic taper potentiometer in the 50 or 100'ish ohm range ? Mouser and Digikey don't show anything, even non-stocked. I'd like to build an adjustable ...
6
votes
2answers
115 views

question about transistor matching circuit

I'm studying this transistor matching circuit provided initially by Bob Moog. I think I mostly understand how it works, the op amp, bjt not under test and resistors form a current source, which stays ...
0
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2answers
38 views

Possible calculation error using current divider rule on a non ideal current source circuit

I am going through my notes in preparation to an exam, the following was taken straight from the board as my lecturer wrote it. As far as im aware the current divider rule should be $$I1 = It * ...
0
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1answer
56 views

Voltage regulator Current regulation

I want to understand the concept of current regulation in the circuit, In my research I came across the following link Boosting Regulator Current for IC 78xx by MJ2955 where in the circuit schematic ...
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2answers
67 views

How do I calculate the voltage in this circuit?

I have the following circuit: I am a beginner at this stuff, so... ;) Ok, the question is to calculate the voltage across the terminals A and B? I have no clue how to do that? You can't just take ...
0
votes
1answer
106 views

Can an opamp be neither in linear region nor saturated?

I'm trying to build a voltage controlled DC current source. For this, I built this circuit: A little bit of context. The voltage supply is 5V. Current range must be from 0mA to 30mA or so. Load ...
0
votes
1answer
80 views

Wide Input Voltage Range Constant Current Source

I would like to design a Constant Current Source of 25mA, With Input varying from 2V to 50V. Please provide just an idea how to get about this.
0
votes
1answer
58 views

Measure Voltage (Divide) on a current source

I need to use a constant current source 20mA, the current flows through multiple diodes and resistors which are in series. The resistor value can vary from 0 to 1.6k and also a possibility of Open. ...
5
votes
1answer
268 views

How do I build the current regulator circuit referred to on the LM337 datasheet?

What I would like to accomplish: I am trying to add current regulators into a home built dual rail linear regulated power supply. I previously asked this question about transformer fusing and ...
0
votes
2answers
113 views

Finding voltages in a circuit with current source

I am trying to understand the basics of current source, but I don't know how to calculate the voltages v1 and v2. I tried to sketch the expression for current divider, but I think I didn't actually ...
0
votes
2answers
137 views

How much current will I get from the 5V rail of a Teensy 3.2 powered over USB? [duplicate]

The microcontroller in question is a Teensy 3.2. My understanding is that the most current that you can get from a standard computer USB port is ~180mA; how much of that will current devices attached ...
1
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0answers
83 views

Constant current source - unexplained issues

I have been puzzling over this for days now, and cannot for the life of me figure it out... I have a constant current source set up to use as an analog dimmer for my LM3429 LED driver. I have made ...
5
votes
2answers
299 views

Adjustable 0-5A voltage controlled current source

I would like to build a high side current source that can source 0-5A with a 1mA resolution. The voltage source feeding into this current source is a variable 0-50V that is always ~3V above the ...
0
votes
1answer
34 views

Voltage source in series with dependent curent source. How to solve for voltage source?

I am trying to calculate the high frequency cut off of a common collector BJT circuit. I replaced Cu with a test voltage and open circuited the other capacitors. The circuit I came up with has the ...
0
votes
1answer
110 views

How to bias BJT using Widlar current source?

Here is Widlar Current source driving load: It gives almost constant current for wide range of load resistances: Here is one circuit involving BJT: You can see it is biased using one voltage ...
0
votes
1answer
85 views

Alternative circuit for obsolete product [closed]

i am looking alternative circuit or module the same as DTL35A-LC. It is a analog/voltage-controlled current sink module. Its output can reach up to 5 Amps that i really need. So can you suggest a ...
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votes
1answer
138 views

Is there a way to get dc out of a capacitor? [closed]

The voltage and current during discharge of a capacitor is describe with an e function. I assume that thus a separate component is necessary (since ...
0
votes
1answer
68 views

3V Current source with low voltage drop

I'm trying to make a IR laser diode driver which needs 1.9V and ~80-100 mA constant current. Most of laser driver circuits in web has LM317 as a current source but that design has always voltage drop ...
2
votes
3answers
105 views

Current mirror improvement by adding resistors

One of the limitations of the current mirror with 2 BJTs is the Early effect. According to the Art of Electronics 2nd Ed., adding emitter resistors should make the circuit "a far better current ...
1
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2answers
311 views

constant current source circuit

I am designing a constant current source(35mA) circuit using transistor.Thought of usingthis below circuit but the problem with that is my resistance R is fixed( 2.3 ohm ) which I could not change due ...
1
vote
2answers
148 views

How do security alarm systems measure zone resistance?

Recent security alarm systems use EOL(R) or DEOL(R) to terminate the line of the zones. Question 1: What method is used to measure the resistance of a zone? I can think of two options: It measures ...
3
votes
2answers
161 views

Temperature compensation in transistor current cource

I am working with analysis of BJT current source. I didn't get the explanation of temperature compensation in NPN transistor with PNP and pull up resistor. How does it work actually?
1
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2answers
113 views

How do I get a low impedance current output from this circuit?

I am learning about the VI characteristics of diodes, specifically nonlinear resistor applications. The circuit in this question is used as an example, but the question applies to any high to low ...
2
votes
1answer
94 views

current mirror circuit using BJT is alternative for LM317 current source?

I learnt about BJT and MOSFET current sources in my textbook,but they are used in IC chips.Is it possible to do our own current sources using BJT like two 2N2222 transistors in current mirror ...
0
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2answers
91 views

Understandig of boost converter

I am currently using boost converter so I made all the calculation to make it work. My question is not about calculation it is about how physically is a boost converter working. Here it is : the ...
1
vote
2answers
90 views

What does this op amp circuit do?

Disclaimer: I have little to no background in electronics / electrical engineering. I believe this circuit is to provide a steady and accurate current source, which can be altered with a ...
0
votes
1answer
193 views

How to find out Processor GPIO maximum source current and maximum sink current of that pin

How to find out Processor one GPIO pin maximum source current and maximum sink current? In datasheet mentioned IoL and IoH, is it same for GPIO source and sink current also?
1
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1answer
80 views

Opposing Ideal Current Sources

So I'm looking at the circuit below and a little confused by it. How are there two current sources facing opposite directions? What does this even mean and how can it be a valid circuit, since ...