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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 ...

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17 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
61 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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22 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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46 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
37 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
85 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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31 views

Solving a driven RL circuit with a current source

I was given a practice problem as listed below. It says that the solution is in the form of a second order differential equation, but I thought that only RLC circuits were 2nd order. Am I missing ...
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44 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
63 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
37 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
22 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
61 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
74 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
50 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
75 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
65 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
61 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
682 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
68 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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1answer
54 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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61 views

Current Pump Circuit

I found this circuit diagram in an academic paper, however, there are no values associated with any of the passive components. The authors claim that this circuit can deliver 1-120mA across a load of ...
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1answer
62 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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52 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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32 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
162 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
32 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
121 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
33 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
31 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
59 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
44 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
84 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
136 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
64 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
101 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
55 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) +/...
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58 views

Atari Punk Console with sequencer to multiple inputs

I designed an APC circuit with two APCs on it and a step sequencer, which basically cycles through a series of potmeters with a 5V voltage to it. When I route the sequencer to one discharge pin on ...
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2answers
98 views

Current Source - MOSFET vs Bipolar NPN/PNP for stability

Consider the schematic below. There are several pro an con for each, I would like to focus here solely on regulation stability. (Not voltage drop or opamp current as this is already answered). I ...
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2answers
72 views

A low power circuit to measure large resistances

I am trying to measure resistances in the range 20 kohm to 1 Mohm. Initially, I was using a constant voltage source, but the power consumption when the R = 1 Mohm is very large. I want to use as ...
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2answers
86 views

Is Joule Thief a constant current source?

Wikipedia describes Joule Thief, shown below, as a circuit that can be used to provide constant load even when voltage of a battery decreases. At least that's what I think the article means. simulate ...
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1answer
45 views

Analysis of a modified Howland Current Pump

I am trying to do an analysis of the following modified howland current pump based on the circuit description in the datasheet of the LMP7701. This is a voltage controlled current pump that is driven ...
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3answers
207 views

Current source with unlimited cap drive op-amp oscillating

I've been trying to create a current source, and have finally gotten my hands on some LM8261's which should be an 'unlimited cap drive' op-amp. The problem is, it is still oscillating... This is the ...
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1answer
80 views

Current source with op amp and transistor

I'm building current source with OP AMP LM358 and MOSFET transistor IRF5305. Here's schematic diagram of the circuit: I have two questions about it: 1) Maximal gate-source voltage of IRF5305 is +/-...
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1answer
122 views

what is the difference between using mosfet and bjt for op amp based current source

I have planned to design a op amp based current source driver for laser,but i came across two design one used mosfet1 at the output of op amp and other used bjt2 what is the difference What is the ...
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2answers
119 views

Reducing noise on a voltage reference

I need a stable, low noise voltage reference that I can adjust between 1.4V and 1.8V. The output should source or sink up to 0.25mA @150Hz max. The output will provide a +1.65V bias for a bipolar ...
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2answers
192 views

Art of Electronics figure 5.87 (revised)

The circuit below comes from the errata of The Art of Electronics. Why is the circuit in Figure 5.87-B (bottom) correct? As drawn, 50 mA at output will mean -5V at the inverting input of the Op-Amp. ...
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59 views

Laplace with source before and after t=0

In my course, there is the following excersise that I should transform to Laplace. I understand that the initial conditions are 3V for the capacitor. For DC current, the capacitor is open-circuited ...
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2answers
435 views

How to make a constant current sink in the pA-nA range

I am tasked with making a constant current SINK for a testing device. It must outputs 4 separate values, -10pA -100pA -1nA -10nA. I need the current to last for at least 10-20 seconds, preferably up ...
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2answers
65 views

Collecting energy from 70-80 Celsius degree heat heat [closed]

I'm assembling a wireless thermostat for radiators. The module is powered with batteries. I searched for a way to recharge the accumulator from the heat generated by the radiator but I could not find ...
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3answers
119 views

Logic circuits use current source or voltage source?

Main question: Do logic circuits use a current source or a voltage source? My assumption is that they use current sources because the standard is to use voltage as the indicator of input and output ...