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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63 views

Op amp controlled LED current

I'm trying to implement a simple current control circuit for an LED from here: https://www.allaboutcircuits.com/technical-articles/the-basics-behind-constant-current-led-drive-circuitry/ The ...
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Current source resistor values in differential amplifier

In this circuit How measure input impedance this differential amplifier in LTspice? the OP has used a 4ma current source in a differential amplifier. I'm taking it apart to learn how it works. I see ...
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Trying to better understand voltage and current sources

I feel like I am going a little crazy here because the more and more I read about these things the less I understand them. So I understand that an ideal voltage source has no output impedance, no ...
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37 views

I have found the Rth=10 ohms, However i can't find the thevenin's voltage(between a &b)

*I converted the wye network into a delta and found the equivalent resistances in parallel and series and got it to be 10 ohms. However i am stuck at trying to find Vth. I tried applying mesh analysis ...
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Why does a source transformation not work in this case?

Circuits 2 and 3 give 3.8 mA as the current through R1 [2k Ohm resistor]. However, why is it not possible to transform circuit 3 to circuit 1? what I did: I tried simulating circuits 2 and 3 below to ...
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Find all currents with mesh analysis

Can anyone help with this priblem?
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376 views

I don't understand current source, voltage source, infinite resistance, zero resistance etc

When I google things like voltage source and current source they talk about things like maintaining a particular level, having infinite output resistance, or zero output resistance, etc. I don't ...
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693 views

Reversed DIP Switch

Simple question, why does the LED lights up when the switch is off
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151 views

Can we explain the differential pair in terms of resistances?

It has always been a big challenge for me to find the most general ideas behind great circuit solutions that can be illustrated by simple electrical concepts... and even by non-electrical analogies ...
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68 views

Would this photodiode sensor work better in series or parallel?

I am working on a photodiode small object sensor that detects and records signatures of objects passing through an array of photodiodes facing an array of IR LEDs. I am connecting the photodiodes to ...
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188 views

Current controlled bridge amplifier

This circuit essentially takes a control input and then doubles it when presenting it to the load. I would like a circuit that controls the current to the load. How would I modify the circuit to do ...
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154 views

How to emulate a capacitor discharge curve using a microcontroller output pin?

I require a configurable amount of capacitance, without using a bank of dozens of actual capacitors and some kind of complicated switchboard, like this: Not only would this be an unwieldy solution, ...
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89 views

Can power outlet be taken as a current source?

Consider a situation where I have a power outlet and I am completely unaware of the internal circuits and the fact that the electricity comes from an ac voltage source supplied by some company. I just ...
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1answer
37 views

How do these current pull-up sources work?

I'm looking at the data sheet for the TPS54160 (https://www.ti.com/lit/ds/symlink/tps54160.pdf). The UVLO feature mentions the use of current pull-up sources l1 and ...
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53 views

Working out theveni. Voltage with no voltage source

How do i get the thevenin voltage having worked out the load impedance and obtained it as 3.415 -j0.7317 ohms
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93 views

BJT Common Emitter - Active Load Biasing

I'm experimenting with/learning about the use of active-loads with a common emitter and I've hit a wall. When using a resistor in the collector it makes sense how the output voltage bias can be set to ...
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42 views

Control capacitor charge current with a GPIO?

I have drawn the following schematic: Vp/Vm are +/-12V rails. The capacitor charges through R1. A 3.3V pulse is produced at regular intervals on an MCU GPIO to turn Q1 "on", short C1 and ...
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44 views

LM13700 control current appearing as voltage at output?

I've got an LM13700 in this VCA configuration, and for whatever reason the gain control input (I'm applying a triangle LFO, ranging from 2-7v) is appearing as a voltage at the output. Does anybody ...
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1.2V AAA rechargeable batteries, voltage for almost full charged cell

Some weeks ago, I bought a new pair of AAA rechargeable batteries, Ni-MH. Its package shows "Panasonic eneloop" model with up to 800mAh. First I connected them in series and connected two ...
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61 views

Thevenin Equivalent Circuit of Ideal Independent Current Source

This is dual to <Norton Equivalent Circuit of Ideal Independent Voltage Source>. I have wrote it to answer a problem <click here> but I need to make it independent which requires ...
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69 views

Norton Equivalent Circuit of Ideal Independent Voltage source

For some purpose I need to derive the equivalent Norton circuit of an ideal independent voltage source. I found that it is impossible to do it. I describe the way I found it below and need comments, ...
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79 views

One milliamp current source for RTD

I am trying to design a one milliamp current source (Howland current source) with a precision of +/- 1 uAmp. The current source will be used to measure temperature with a 3 wires RTD sensor (H-T-01-12-...
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67 views

Working of op-amp based current source

Can anyone please explain me the working of the circuit attached? I believe the op-amp U1 is connected to provide a stable DC voltage at the non inverting terminal of U3. Is my approach correct? The ...
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Problems regarding KCL & KVL

Question: Below figure represents an approximate equivalent circuit of a field effect transistor amplifier. Using KCL find the output voltage \$v_2\$ in terms of input voltage \$v_1\$. My try: I ...
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86 views

Oscillations in parallel-RLC network with a limiting VCCS

Here is a parallel-RLC network (where G = 1/R is the admittance) with a limiting VCCS. The characteristic of the VCCS is shown in Fig (b), where the slope is G1. The problem asked is as follows: Find ...
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5answers
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How can I make a current source that can supply 1uA?

Is there anyway I can make a constant current source which has an output of 1uA or can I get it from the market? The load is around 200kOhms, and I need accuracy to 1%.
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Why can we bias MOSFET with current source?

My question is: If I have properly set VGS to prevent MOS from turning off, then if we biase a MOSFET with a constant current source, how can we conclude that it is working at saturation region? How ...
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73 views

Two independent current sources with one opamp?

simulate this circuit – Schematic created using CircuitLab The above circuit delivers a predetermined current to the load: $$i_L=-\frac{u_s}{2R}$$ Is it possible to extend it, so that it does ...
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48 views

What is causing the DC Offset in Mirrored Howland Current Pump Circuit

I am creating a current source to try to expand my knowledge about electronics design. After some research I decided to build the Howland setup since I want to develop a bipolar current source. The ...
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28 views

dependent current source polarity

In this question, I apply the current cycle law, I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here. ...
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53 views

op amp - current source - voltage output

I have the electronic schematic bellow composed with two op amp and I want to determine the voltage output of the X2 op Amp. I m a little bit confusing about the aim of using the zener diode D1 in ...
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410 views

Why is the voltage drop created by a current source added?

A few days ago a similar question was asked for the simple circuit below consisting of three elements in series (voltage source, resistor and current source). Despite professional explanations, the OP ...
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41 views

Underdamped RLC with CCCS, calculating capacitor voltage

Referring to "Electrical Circuits" Nilsson/Riedel 10th Edition. I have a classic underdamped RLC circuit with a CCCS (Current Controlled Current Source) with a current multiplication factor ...
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48 views

[op amp - Gain current source - current reference]

I have a question about the formula to consider for calculation of the gain for the electronic bellow. Thanks for your support.
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126 views

op amps comparator or differential amplifier

I have a part of electronic schematic as described bellow, I'm a little bit confusing about the function of the LM321 amplifier. In this case, can we say that is a differential amplifier or just a ...
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52 views

Need help for pointing out, source follower circuit with current source, designing NMOS

I'm not sure did I solve this problem right. I made \$ r_{o2} \$ , which is resistance looking at Q2 drain. So I can get $$ g_{m,Q3} = 1.8m(A/V) $$ from $$A_v = \frac{r_{o2} || r_{o3}}{1/g_m + (r_{o2} ...
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55 views

LM317LM as a current source

I have been using LM317L as a current source for generating 2-50mA current for a load, by following the datasheet, P14: So far so good, but now I have come across LM31L-n, particularly LM317LM/NOPB, ...
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72 views

Opamp input bias current and current sources

I have a current source connected to a load and I want to measure the voltage at the output of the source, and therefore I would like to buffer this voltage. In this configuration, I am under the ...
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52 views

Circuit for OpAmp-MOSFET based constant current source for 0.2 - 1.5A

I'm a beginner in electronic circuit design and have designed my first Voltage based constant current source using OpAmp driven MOSFET (based on this). The intended current output needs to be ...
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35 views

JFET Constant Current Source (CRD alternative)

Today I have build constant current source based on J111. To drain I connected VCC it's 24VDC from laboratory power supply, then I connected resitor 470Ohm between gate and source. To source pin i ...
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46 views

PMOS and NMOS Current loads in Common Source Stage

I am new to the concept of Single Stage amplifiers design using CMOS. In that, I came across a concept of using current source as loads in design of Common Source Stage, where it was mentioned in a ...
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55 views

Fixed current source

Thank you for reading this question and forgive me if I sound naive. I am working with a device that uses 4-20mA as set-point, I need 3 fixed values to work with this device: (4mA, 12mA, 20mA) The ...
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27 views

Measuring current output of a diode driver

I have a laser diode driver chip that can produce DC currents up to 200mA. The current is adjusted by a potentiometer on the driver chip. The driver chip has four pins: inputs: GND, SUPPLY outputs: ...
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Constant current source with MOSFETs

I have a question regarding this constant current source circuit: I have seen this circuit with two BJTs (like in the figure), but sometimes T2 is a MOSFET (I assume for lower Rdson resistance and ...
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1answer
69 views

Meaning of “A voltage source “likes” an open-circuit load”

I read a book "The Art of Electronics" by Paul Horowitz, Winfield Hill. In the book, I saw some phases. A voltage source “likes” an open-circuit load and “hates” a short-circuit load A current ...
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What are some practical examples of a constant current source?

Please don't state the obvious that nothing is a perfect constant current source. And please do not give examples of how to create them from components. I looked at this SE Q/A which stated the ...
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32 views

Efficient current drive with arbitrary waveform

I need to drive a defined, arbitrary current waveform into an output with a load impedance that may not be constant. Currently, I am using this: The 100V is created from 9V dc using a standard boost ...
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71 views

Oscillations in voltage-controlled current source with MOSFETs and opamp feedback — Why?

I have a circuit that should operate as a voltage-controlled push-pull current driver, able to source or sink at least 2A (into a 1 ohm load). It has unexpected oscillations on the output current. ...
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51 views

4mA-20mA loop behaviour when out of range

I have a temperature sensor that records temperatures from 10ºC to 30ºC, but in my project they only want temperatures to be read in the range of 15-25 with 4ma when 15 and 20ma when 25.My problem is ...
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Mesh current method problem with voltage controlled current source

I'm signed up recently to this site but i need help for my Fundametal of Electrical Engineering course.I need to find power of the current source. Thank you. Note: (y is equal to 2)

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