Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
0answers
22 views

Correcting DC offset in op-amp based controlled current source

In an attempt to develop an automated potentiometer measuring device I have implemented the following op-amp based voltage controlled current source, controlled by the output of a DAC. The voltage ...
0
votes
1answer
34 views

Find the Thevenin equivalent of the circuit [on hold]

To find the open circuit voltage between C and D, can I assume that no current flows through the current source between A and B. If it does not, the Thevenin voltage is 10V. But since it is not an ...
0
votes
1answer
52 views

Paralleling Multibit current DAC: Improving Accuracy by Averaging

No doubt that if I put in parallel n DACs, multibit (i.e. 16 bit) current output R2R ladder chips, I get n-times higher current at the summing node and the output impedance is also reduced by "n". ...
0
votes
0answers
63 views

Transistor current source \beta varies (AoE Ex. 2.23)

I am having trouble solving the following exercise: Exercise: If \$ \beta \$ varies from 50 to 100 for collector voltages within the output compliance range, how much will the output current vary? (...
0
votes
1answer
54 views

Topology choice for wide-output-voltage-range SMPS

I'm intending on building a off line (230VAC), 50W, isolated, constant-current switch mode power supply. This by itself is not a big challenge with the plethora of application notes and examples ...
0
votes
2answers
31 views

Variable Current Amplifier for Fan Control

I'm working on a project where I need to vary the current supplied to a DC fan. I am currently trying to use a BJT as a current amplifier to amplify a low current analog output (0 to 100 mA to vary ...
0
votes
1answer
41 views

Superposition with dependent sources

If the value of a dependent source (say CCCC) depend on the value of an independent source (say a current source). When setting the current source to 0, would that make the CCCC an open circuit (i.e. ...
2
votes
2answers
78 views

Turning off the LM3914 dot/bar display driver per the datasheet

I'm designing a circuit with an LM3914 dot/bar display driver and want to shut off the entire bank of LEDs based on conditions in the circuit. I'm having some difficulty turning off the driver from ...
2
votes
2answers
60 views

Thévenin's Theorem Example

I just started learning Thévenin's Theorem. My textbook gives the following example: I'm referring to online sources such as this to complete this problem. However, all of the circuit diagram ...
0
votes
1answer
20 views

Explanation of Source-Absorption Theorem Example

In the section on the Source-Absorption Theorem, my textbook has the following example: I was wondering: If the voltage $$v_\pi = - v_e,$$ then why do we get $$g_m v_\pi = g_m v_e$$ instead of $$g_m ...
0
votes
1answer
60 views

Variable Constant Current Supply

I've been looking around for a good CCS schematic, and decided to try making a simpler one even if it means it'll behave worse. I need a 12V (would come from an ATX power supply, more than enough ...
0
votes
0answers
35 views

AC Current Source - Modifiable Amplitude and Frequency

Just a heads up, I am not an electrical engineer. I need to build an AC current source of the following specifications. I have looked into IC chips, but none meet my specifications. I have started ...
0
votes
1answer
49 views

Current through a diode changes for the same forward voltage in two circuits

In LTspice IV, I am simulating a 1N914 diode behavior in response to a variable current source in two circuits. One circuit has just the current source and the diode, and the other has the current ...
0
votes
2answers
55 views

Resistive circuit analysis with dependent current and voltage source

The question in a study book says to find the current through R2. I have very little experience dealing with dependent current and voltage sources, so I get thrown off when performing loop current (...
1
vote
2answers
71 views

Figuring out the principal working of constant current source

I've the following circuit: simulate this circuit – Schematic created using CircuitLab I was told that this is a constant current source. I think that the resistors \$\text{R}_1\$ and \$\text{...
0
votes
1answer
78 views

LTSPICE Simple MOS-FET Stacked Current Mirror/Cascode saturation threshold less than expected

I am running a few very rudimentary cmos circuits in LTSPICE. For some reason, when designing stacked mirrors, I seem to get a much lower saturation turn on thresholds would be expected. I've tried ...
2
votes
4answers
123 views

Mosfet constant current

I am looking at a schematic that has a very similar form to a emitter follower but in the mosfet world. It's intended to keep the brightness relatively constant as the battery battery voltage ...
1
vote
1answer
144 views

Constant current source with shunt fet

I'm want to create a project with a LED strobe with IR LEDs. As LEDs the Osram SFH 4249-UV will be used in strings of 15 LEDs and 32 strings parallel. This results in a Vf of 34.5 - 45 V and a If of ...
-1
votes
1answer
72 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.
1
vote
2answers
115 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 ...
0
votes
2answers
80 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 ...
0
votes
0answers
32 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 ...
0
votes
1answer
26 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. ...
0
votes
0answers
86 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 ...
0
votes
1answer
61 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 ...
0
votes
0answers
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 ...
-2
votes
4answers
81 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 ...
-6
votes
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 ...
1
vote
1answer
45 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 ...
1
vote
1answer
348 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 ...
5
votes
1answer
410 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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
0answers
24 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 ...
0
votes
2answers
67 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 ...
0
votes
1answer
31 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. ...
1
vote
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 ...
0
votes
1answer
65 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 ...
0
votes
4answers
115 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
0
votes
2answers
55 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 \$...
0
votes
1answer
115 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, ...
0
votes
1answer
64 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 ...
0
votes
1answer
32 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 ...
0
votes
1answer
80 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 ...
2
votes
2answers
86 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 ...
0
votes
2answers
58 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 ...
1
vote
3answers
105 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 ...
1
vote
2answers
107 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 ...
1
vote
1answer
66 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). ...
3
votes
1answer
741 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 ...