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Questions tagged [current-source]

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 supplying current to) and have an infinite output impedance. In non-ideal implementations current sources have limited operating ranges and finite output impedances.

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67 views

Find the current at the resistor

I've tried to divide current at 8A and then make a Kirchhoff voltage law between the resistor and dependent current source but I still can't solve it.
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45 views

Plot voltage for different resistor values in LTSpice

I've signed up for a SPICE course at work, that will take place on Monday and I'm desperately trying to learn electronics and SPICE. (I work as an embedded engineer but with very lacking electronics ...
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61 views

How do I make constant current? [duplicate]

I have a load that has varying resistance with external pressure. In order to measure the change, I am trying to measure the voltage on the load, when constant current is applied. And the circuit ...
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62 views

Led driver high current and voltage

For a project I have to design a led beacon that will consist of +400 LEDS. These LEDS will be driven only a short amount of time maximum of 3% duty cycle (frequency: 100Hz, pulse: 300us). The LEDS ...
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28 views

How do I use a current source for a pulsed voltage in LT Spice?

For an LT Spice simulation I was doing of a transformer, I would like to set the current to 3 amps for a power supply, but I'm not sure how to use a current source for that. I tried putting two ...
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1answer
23 views

How to determine sign across current source?

I'm confused about how to determine sign orientation for current sources in circuits. From what I understood initially, it's negative to positive for both independent and dependent current sources. ...
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78 views

constant voltage source + constant current source with transistors

I need a "driver circuit" for my amplifier. It consists of a dynamic current source, a constant voltage source and a constant current source like shown below: The constant voltage source should ...
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1answer
51 views

Adjustable voltage source 10 – 50 V and adjustable current limiter 2 – 70 mA

I would like to build a source that gives on the output an adjustable voltage from 10 V to 50 V and that current be limited from 2 mA to 70 mA or make some circuit that let me choose 2 mA, 1 0mA, 50 ...
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45 views

Understanding Optimization/Realization of the voltage controlled current source

I am unable to make a voltage controlled constant current source. So I am using the following scheme (Sorry for bad sketch drawing): The constant control voltage varies in the range of 0 to 5 V is ...
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78 views

Conventional current (DC) [duplicate]

I m confused in the direction of current flow as I studied that current flow from + to - But current flow from negative to positive also called electron flow... & Also current which flow from ...
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1answer
50 views

Struggling with current deductions

A practical current source with a 1-A short-circuit current and 100-ohm internal resistance is to be used to deliver 1/12 A to a 100-ohm load. Determine an external resistance that can be placed ...
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1answer
40 views

LED current source circuit design concerns

TL;DR: Read the bulleted list below. I am designing a simple constant current source to power up some LEDs inside arcade buttons. My project consists of 20 of these buttons. Every button is ...
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1answer
140 views

How to simulate constant current - constant voltage source in LTspice

I am trying to build the CCCV (voltage limited current source in LTspice, having following characteristics: Sources defined current until voltage at the terminals reaches defined voltage, then keep ...
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1answer
401 views

Why is my transistor beta lower than expected?

I bought these transistors on digikey: BC549CTA Reading through the datasheet, (and on digikey's page), I am led to believe that the DC gain for this transistor is at minimum 420 [@ 2mA, 5V]. The ...
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1answer
54 views

1st order circuit analysis

I'm having trouble with this exercise which I don't have a solution for, I'm used to dealing with simpler 1st order RL or RC circuits. Mostly I'm a little confused with the sinusoidal generator and ...
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2answers
25 views

Issue understanding pin functions of a programmable current source from manual?

Here is the link to the manual: https://www.analog.com/media/en/technical-documentation/data-sheets/3092fc.pdf I am confused about the pin functions, in particular IN and SET (page 8). I gathered ...
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21 views

High voltage current source for TVS testing

I need to build a simple device for TVS diodes testing. For that test, I need to generate an 80V pulse (10 us width I think) with 1 mA current limit. The things that come up to my mind are current ...
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2answers
64 views

How to find the current in this circuit?

Please help me find the current flow in A1,A2 and A3. its my First FEE class and I was able to solve this with voltage source but with current source Iam Having trouble. also V1 and V3 are the ...
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1answer
24 views

Depletion Mosfet as current source to power load

I came acros the following application note for a Depletion Mosfet (https://www.infineon.com/dgdl/Infineon-Application_Note_Applications_for_Depletion_MOSFETs-AN-v01_00-EN.pdf) and i got intrigued. ...
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1answer
54 views

Understanding some mistakes, when trying to find the Thevenin equivalent

I was asked to find the Thevenin-Norton equivelant, and I got stuck on some things that I can't quite understand. I don't know if i need to be more specific. What's wrong with the following? And why ...
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1answer
48 views

Minimalistic LT3080-1 current source

I am trying to design a minimalistic current source to drive an LED from a lithium polymer battery and with a small number of components to minimize board space usage. First I wanted to use the same ...
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4answers
96 views

Inductor with constant current source

Hii can anyone explain how to do this. Its Given Answer as 6A. What exactly happens when a constant current source in series with inductor? TIA
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2answers
50 views

Differential equation for current driven RC circuit

I need the differential equation for the following circuit for numerical integration purpose. It is driven by a time dependent current source. So the question is: How can I know \$U(t+dt)\$ given \$...
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1answer
85 views

How to find voltage on zener diode while there is a current source

simulate this circuit – Schematic created using CircuitLab I'm confused about whether zener is on or off due to not being able to know voltage on V0. I tried to find by applying KCL & KVL, ...
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1answer
55 views

Stable 200uA Current source by cascading REF200's Current source and Current mirror

I am trying to work on above circuit. A common operating point of ISFET pH sensor is a drain-source current of 100 uA and a drain-source voltage of 500 mV. I am using REF200 current source to feed ...
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1answer
29 views

NTE 4050 buffer and current sourcing capability, datasheet reading woes

I am trying to construct an output that is switched on by the inputs to a buffer. The buffer input, in the final design, will be sourced from an Arduino or Raspberry PI. I needed the buffer because ...
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1answer
67 views

Differential transimpedance amplifier

I have found an opamp schematic that I don't understand. As far as I know a transimpedance amplifier "converts" my input current into an output voltage. But in this case the positive and the negative ...
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2answers
80 views

How do I keep this VCCS stable?

I have designed a circuit to measure impedance of certain tissues. It injects a constant current from two electrodes and measures the voltage at different electrodes. The system mainly consists of a ...
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2answers
57 views

Sink or Source a servo drive output?

I have a servo drive with 5 digital outputs. I will be connecting one of the outputs to a 24v relay to disable the drive if a fault occurs within the drive. The manual gives two schematics using ...
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3answers
89 views

How can I increase the load capacity of this circuit?

I'm not into the current source subject much, but the following circuit provides constant current to the load up to around 500 Ohm: Here below is the plot of Rload versus Iload: How can this circuit ...
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2answers
84 views

Voltage across capacitor in charging RC circuit with constant current source

simulate this circuit – Schematic created using CircuitLab I couldn't really figure out how to get the switch that I wanted but this is functionally the same. Before the switch flips, there's ...
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1answer
63 views

Creating chained digital current loop

I need to send some digital data and power for long distance (around 60 meters) using only 3 wires. Data speed is low, something like 100bps is enough, 1000bps would be perfect (12.5Bps and 125Bps). ...
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1answer
702 views

How to determine op-amp gain with active feedback?

The Howland current pump uses an op-amp in the configuration below with a resistive feedback network which gives me the gain show below: But if I decide to swap the feedback resistor for an ...
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1answer
77 views

Find potential difference between nodes A and B in circuit below

By KVL and KCL Ix = 4A and Iy=Iz=6A The potential difference between A and B = Va - Vb = 6 +8Ix =38V I don't understand how we calculated the potential difference using KVL and KCL
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58 views

Electrical Impedance Tomography (EIT)

I am trying to replicate the circuit in this paper: http://chrisharrison.net/projects/electrick/electrick.pdf I have followed the schematic in Figure 7 and utilized Howland current source as ...
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1answer
68 views

MP111 Op-Amp: Non-linear gain at low input voltages?

I'm currently using the MP111 hybrid op-amp set up as a voltage controlled current source with a gain of 1. But what I'm finding is that at low input voltages the gain is much higher than it should ...
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0answers
57 views

Designing a constant current pulse circuit

I'm looking for help designing a constant current pulse through a variable load impedance of 10-100k (R4). The ideal response is shown below. This waveform was measured from an off the shelf ...
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0answers
33 views

Measuring resistance of switched load

I am in the process of designing a custom vaporizer. So the main coil with a resistance ranging from 0.2 Ω to 2 Ω is switched using a MOSFET shown in the circuit diagram below. ...
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4answers
322 views

Constant current source with MOSFET, OPAMP and Instrument Amp

UPDATE Based on the information from everyone answering below, I have modified my circuit and the oscillation has completely vanished! I started performing small modifications in order of easiest to ...
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1answer
33 views

add different current loads to test noise on DC-DC converter

I want to test the LTM8021 DC-DC converter (using an eval board I bought - schematic for it is below) for noise output at varying current loads (10mA, 100mA, 200mA, 450mA) and still fairly new to this....
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2answers
124 views

Current Regulation Drift

Consider this current regulation circuit, where a load is connected between a rail and D: R1 is 56k, C122/123 are 300pF, R201 47k and R200 680ohm The circuit works fine, but there is something that ...
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1answer
34 views

What does it mean if input impedance given as a current regulator?

This SSR relay has an input impedance given in its datasheet as: It says "Nominal Input Impedance is a current regulator". At 5V 16mA. But how can I model this type of input impedance? I will use ...
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2answers
32 views

Source transformation violation

Using thevenins or norton theorem, we can easily find current through the resistor as 1 amps. But if we convert the current source to voltage source , current turns out to be zero amps . Why?
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1answer
73 views

Source transformation with impedance being inductor or capacitor

I found a presentation that states the following about source transformation when the impedance is capacitive/inductive: While electrical circuits books, like Nilsson's, says: If I transform the ...
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1answer
49 views

Calculating current in one branch of circuit

I want to calculate the current labeled in the diagram \$i\$. I am thinking that since there is 3V it would be as straightforward as \$\frac{3V}{6\Omega}\$ for the current in that branch labeled. Is ...
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1answer
116 views

Can a Dependent source be dependent on itself?

I am looking for the Thevenin Resistance here. However, I have no clue what to do with \$i_b\$ and the source dependent on it. This is the entire circuit. \$i_b\$ is the current through the 5\$k\...
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3answers
291 views

How do I get 5V 10A output from a 3.7V li-ion battery for 64x16 led matrix display module?

Please I am new to electronics and new here. I'm doing a project which involves the use of a 18650 li-ion battery (or two as may be the case) to power a 64x16 led matrix display module which (...
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2answers
84 views

current sink/source in ADS114S06B analog/digital converter

Here is the datasheet. It seems from the graphs on page 17 that the I/O pins will sink or source as much as 7.5 mA: However on page 9 the table indicates an expected sourcing of 1 mA (I say expected ...
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2answers
107 views

Trying to solve a circuit containing 2 current sources and 1 voltage source and resistors: what am I doing wrong?

Here is the schematic and the values given. This is for a Coursera test on Linear Circuits I am taking and where I am stuck :-( Doing KCL and KVLs I get this: $$ \frac{V_a-V_b}{R_1}=I_1+i_B\\ i_A+...
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2answers
56 views

Current drawn by a motor driver

Only interested in the binary logic part, not the motor side. The datasheet specifies a few absolute max ratings: Table 4. Absolute maximum rating IIN Input current (INA and INB pins) +/...