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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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4answers
115 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 ...
0
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1answer
30 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....
4
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2answers
98 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 ...
1
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1answer
31 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 ...
0
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2answers
29 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?
2
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1answer
49 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 ...
1
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1answer
36 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 ...
0
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1answer
61 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
80 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 (...
1
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2answers
42 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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0answers
22 views

Independent Current Source and Current Controlled Voltage Source Problem

Can someone point me in the right direction to solving for V0? I tried to divide the current using ix = is*(6^-1 / (6^-1 + 2^-1)) but wasn't getting the right answer. I'm sure the CCVS makes it so ...
2
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2answers
94 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
54 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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0answers
44 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 ...
0
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2answers
90 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 ...
0
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2answers
60 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 ...
0
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2answers
70 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 ...
0
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1answer
29 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 ...
4
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3answers
190 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
51 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 +/-...
1
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1answer
64 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 ...
2
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2answers
104 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
184 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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0answers
54 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
308 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 ...
1
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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 ...
0
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3answers
108 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 ...
1
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0answers
68 views

Question on inductors with initial current

Question: Initially the switch position is aa', 3 H is connected across a 3 A supply and 6 H is connected across 6 A supply. After some time the make before break switch is actuated to the new ...
0
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1answer
91 views

Which design to choose for highly stable LED or laser diode driver?

I'm looking at several design choices for driving a LED and/or laser diode in a very stable, low noise way. The specs are as follows: current: 1-100mA, adjustable (the adjustment can be either ...
0
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3answers
196 views

How to make a low pass filter of current, instead of voltage?

Is there a way to low-pass filter current, rather than voltage? Let's suppose there is a circuit consisting of a current source and a load. The current source may have a little bit of current ...
0
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1answer
54 views

What is the input and output impedance of a Widlar current source?

The Widlar current source is illustrated below: simulate this circuit – Schematic created using CircuitLab The small-signal AC model is shown below: simulate this circuit I know that if the ...
1
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1answer
61 views

LM13700 Bias Current via Resistor vs. Voltage-Controlled Current Source

I am trying to understand the advantage of using a voltage-controlled current source (VCCS) to drive the bias current inputs of an LM13700 OTA, compared to a simple application of the control voltage (...
4
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1answer
74 views

Can any power supply be made a current source with this circuit?

The other day I built a basic buck power supply on a breadboard from scratch (i.e. sawtooth generator, comparator, zener power supplies for control circuitry and references, feedback loop, and low-...
0
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0answers
24 views

LTspice modelling for the end terminal side

So I have this model. I am trying to build a current/voltage converter circuit for a bus carrying current to the other end of the bus, because I need to give this voltage output from the amplifier to ...
1
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1answer
99 views

What will happen if a dependent voltage source in parallel with a dependent current source?

What will happen if a dependent voltage source in parallel with a dependent current source. like dependent voltage source: 4Vx and current source 3Ix in parallel.
1
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1answer
22 views

variable regulation source

I am learning electronics and I want to make a , variable regulation source for a soldering iron, which works at 50W, how much voltage and amps should have the output? For the soldering iron works ...
2
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1answer
41 views

Is the carbon-zinc battery that I am characterising overloaded? Using HPPC

I am trying to characterise a 9 V battery using a pulsed load measurement. The battery is a 9 V zinc-carbon eveready super heavy duty. The load is a controllable constant current source. When I ...
3
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3answers
189 views

How to find the value of alpha in this curcuit?

I have tried to solve this way but i am not sure how to proceed from here: [![tried solution][2]][2]
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2answers
161 views

Charging a 4000mAh Li ion battery using multiple TP4056 ICs

As single TP4056 IC rated current is 1A,so I was thinking to connect multiple TP4056 ICs in parallel, such that enough current can be sourced to charge the li-ion battery(400mAh) connected. Here is ...
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0answers
18 views

Wide voltage range digital input with constant current sink

I'm building a device which should have a few digital inputs suitable for "industrial environments". The design of the input circuitry proved to be more involved as expected, since the following ...
0
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2answers
206 views

How to calculate this two transistors Constant Current Source circuit?

I came across a constant current source calculator at Electronic Product website:enter link description here For example, for a 13.5V input, 300mA output, it comes out the following parameters: <...
2
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1answer
100 views

~40 uA current sink… what current mirror topology to use?

I need to sink a constant 20-60 microamps from the inverting input terminal of an op-amp in order to shift the output voltage upwards a bit. This is a pretty low-speed circuit, with little spectral ...
2
votes
3answers
67 views

How can I “filter out” a small offset current from a current source?

I have a current source that produces a 1 kHz 1 mA sinusoidal current. Unfortunately it also outputs a small DC offset current (microamps). The current source does have a small trim pot to zero out ...
0
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2answers
97 views

Add constant current to an XL6019 module

I need to add a circuit to an XL6019 module to get a constant current (adjustable) source to drive some SMD LEDs. I'm no expert in complex circuits and my level of knowledge in electronics is basic. ...
1
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1answer
47 views

Do we have a voltage drop across this ideal current source?

Additional info includes Vss=0V, Vdd=3V. Also assume saturation (since we have Vd=Vg) and λn=0. We also know the reference current but not the Resistor. I know Vgs and thus Vds but I am looking to ...
2
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1answer
47 views

Nodal analysis: how can I represent the current i2 in terms of voltage over R2?

I am doing the nodal analysis of this circuit: I have successfully wrote the current equations for node A, using nodal analysis, that I found it to be: ...
1
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1answer
49 views

Connect DAC IC to current sinking controller

I want to supply a 0-5V signal to this process controller using the DAC8555. The DAC8555 datasheet states: Each output buffer amplifier is capable of [...] driving a load of 2kΩ in parallel with ...
0
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1answer
66 views

How do this become a Iref current source?

It is a Iref current source unit It is PFET. It is used in one of the data converters block. What is it and how does it work?
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0answers
58 views

20 mA current loop speed/distance trade offs?

By 20 mA current loop, I'm referring to digital current loop communications, e.g. the standard used by old Model 33 teletypes. (Image credit: By Rama & Musée Bolo - Own work, CC BY-SA 2.0 fr, ...
3
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1answer
204 views

LM317 intermittent current source

I need a 50 mA current source despite the load value (resistor LOAD), and I need the current flowing just when the microcontroller says so. It works fine with LOAD = 0 ohm and IL = 50 mA, but when I ...