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 ...

learn more… | top users | synonyms

-1
votes
0answers
22 views

BI-Polar Current Source driven by microcontroller

I want to design a Bi-polar current source and drive it using microcontroller. Design Parameters: Voltage to source = +12V to -12V Current = 0 - 6AMPs Digital Interface (DAC) = 0-5v I am ...
1
vote
1answer
75 views

What is this circuit called? (Dual of a boost converter)

A boost converter is a circuit that uses power from a voltage source, to act as another voltage source with a greater voltage. To conserve power, it draws more current from the input than it provides ...
0
votes
1answer
37 views

Current Source Transformation

So my question is: Can I transform the current source I1 with R5 into a voltage source? I know for sure that if R3 was not in between them I could, but does it make a difference? I am not sure. ...
0
votes
1answer
46 views

Bipolar Voltage to Current Converter

I need a circuit or component which converts bipolar voltage to bipolar current. I have found the XTR111 from Texas Instruments and the 1B22 from Analog Devices. However, they only convert 0-10 V to ...
3
votes
2answers
64 views

PT1000 2 wire probe. Can I add third wire?

I'v got 2 wire (81 cm) PT1000 probe which I want to utilize in a project. I would like to use current source and couple of opamps to make the measurement through ADC (uC) just like described here: ...
0
votes
0answers
56 views

How to drive a capacitor from an AC current source

I am wondering how it is possible to drive a constant ac current through a capacitor. I would like to use a transistor as the current source/sink. The problem is that if I put the capacitor in the ...
0
votes
2answers
67 views

audio-taper potentiometer in 50-100 ohm range [closed]

Anyone know where to source an audio or logarithmic taper potentiometer in the 50 or 100'ish ohm range ? Mouser and Digikey don't show anything, even non-stocked. I'd like to build an adjustable ...
6
votes
2answers
90 views

question about transistor matching circuit

I'm studying this transistor matching circuit provided initially by Bob Moog. I think I mostly understand how it works, the op amp, bjt not under test and resistors form a current source, which stays ...
0
votes
2answers
35 views

Possible calculation error using current divider rule on a non ideal current source circuit

I am going through my notes in preparation to an exam, the following was taken straight from the board as my lecturer wrote it. As far as im aware the current divider rule should be $$I1 = It * ...
0
votes
1answer
46 views

Voltage regulator Current regulation

I want to understand the concept of current regulation in the circuit, In my research I came across the following link Boosting Regulator Current for IC 78xx by MJ2955 where in the circuit schematic ...
1
vote
2answers
60 views

How do I calculate the voltage in this circuit?

I have the following circuit: I am a beginner at this stuff, so... ;) Ok, the question is to calculate the voltage across the terminals A and B? I have no clue how to do that? You can't just take ...
0
votes
1answer
85 views

Can an opamp be neither in linear region nor saturated?

I'm trying to build a voltage controlled DC current source. For this, I built this circuit: A little bit of context. The voltage supply is 5V. Current range must be from 0mA to 30mA or so. Load ...
0
votes
0answers
35 views

Which resistor should I pick among “several resistors ”under voltage source, when using source transformation method?

I got stuck solving source transformation problem , I am sure that the second circuit is obtained after apllying 2 source transformations. As You can see in this example, the 30 Volt Voltage source ...
0
votes
1answer
58 views

Wide Input Voltage Range Constant Current Source

I would like to design a Constant Current Source of 25mA, With Input varying from 2V to 50V. Please provide just an idea how to get about this.
0
votes
1answer
56 views

Measure Voltage (Divide) on a current source

I need to use a constant current source 20mA, the current flows through multiple diodes and resistors which are in series. The resistor value can vary from 0 to 1.6k and also a possibility of Open. ...
3
votes
1answer
132 views

How do I build the current regulator circuit referred to on the LM337 datasheet?

What I would like to accomplish: I am trying to add current regulators into a home built dual rail linear regulated power supply. I previously asked this question about transformer fusing and ...
0
votes
2answers
74 views

Finding voltages in a circuit with current source

I am trying to understand the basics of current source, but I don't know how to calculate the voltages v1 and v2. I tried to sketch the expression for current divider, but I think I didn't actually ...
0
votes
2answers
93 views

How much current will I get from the 5V rail of a Teensy 3.2 powered over USB? [duplicate]

The microcontroller in question is a Teensy 3.2. My understanding is that the most current that you can get from a standard computer USB port is ~180mA; how much of that will current devices attached ...
0
votes
0answers
72 views

Constant current source - unexplained issues

I have been puzzling over this for days now, and cannot for the life of me figure it out... I have a constant current source set up to use as an analog dimmer for my LM3429 LED driver. I have made ...
0
votes
0answers
33 views

Constant Current Source - Variable Power

I am planning to carry out an experiment whereby I have to heat a graphite heater .Dimensions are length- 15 cm, Dia - 1 cm. My requirement is to vary the watt-density on the ...
5
votes
2answers
225 views

Adjustable 0-5A voltage controlled current source

I would like to build a high side current source that can source 0-5A with a 1mA resolution. The voltage source feeding into this current source is a variable 0-50V that is always ~3V above the ...
0
votes
1answer
31 views

Voltage source in series with dependent curent source. How to solve for voltage source?

I am trying to calculate the high frequency cut off of a common collector BJT circuit. I replaced Cu with a test voltage and open circuited the other capacitors. The circuit I came up with has the ...
0
votes
1answer
75 views

How to bias BJT using Widlar current source?

Here is Widlar Current source driving load: It gives almost constant current for wide range of load resistances: Here is one circuit involving BJT: You can see it is biased using one voltage ...
0
votes
1answer
79 views

Alternative circuit for obsolete product [closed]

i am looking alternative circuit or module the same as DTL35A-LC. It is a analog/voltage-controlled current sink module. Its output can reach up to 5 Amps that i really need. So can you suggest a ...
-4
votes
1answer
133 views

Is there a way to get dc out of a capacitor? [closed]

The voltage and current during discharge of a capacitor is describe with an e function. I assume that thus a separate component is necessary (since ...
0
votes
1answer
53 views

3V Current source with low voltage drop

I'm trying to make a IR laser diode driver which needs 1.9V and ~80-100 mA constant current. Most of laser driver circuits in web has LM317 as a current source but that design has always voltage drop ...
2
votes
3answers
67 views

Current mirror improvement by adding resistors

One of the limitations of the current mirror with 2 BJTs is the Early effect. According to the Art of Electronics 2nd Ed., adding emitter resistors should make the circuit "a far better current ...
0
votes
2answers
198 views

constant current source circuit

I am designing a constant current source(35mA) circuit using transistor.Thought of usingthis below circuit but the problem with that is my resistance R is fixed( 2.3 ohm ) which I could not change due ...
1
vote
2answers
118 views

How do security alarm systems measure zone resistance?

Recent security alarm systems use EOL(R) or DEOL(R) to terminate the line of the zones. Question 1: What method is used to measure the resistance of a zone? I can think of two options: It measures ...
3
votes
2answers
85 views

Temperature compensation in transistor current cource

I am working with analysis of BJT current source. I didn't get the explanation of temperature compensation in NPN transistor with PNP and pull up resistor. How does it work actually?
1
vote
1answer
76 views

How do I get a low impedance current output from this circuit?

I am learning about the VI characteristics of diodes, specifically nonlinear resistor applications. The circuit in this question is used as an example, but the question applies to any high to low ...
2
votes
1answer
70 views

current mirror circuit using BJT is alternative for LM317 current source?

I learnt about BJT and MOSFET current sources in my textbook,but they are used in IC chips.Is it possible to do our own current sources using BJT like two 2N2222 transistors in current mirror ...
0
votes
2answers
78 views

Understandig of boost converter

I am currently using boost converter so I made all the calculation to make it work. My question is not about calculation it is about how physically is a boost converter working. Here it is : the ...
1
vote
2answers
88 views

What does this op amp circuit do?

Disclaimer: I have little to no background in electronics / electrical engineering. I believe this circuit is to provide a steady and accurate current source, which can be altered with a ...
0
votes
1answer
95 views

How to find out Processor GPIO maximum source current and maximum sink current of that pin

How to find out Processor one GPIO pin maximum source current and maximum sink current? In datasheet mentioned IoL and IoH, is it same for GPIO source and sink current also?
1
vote
1answer
57 views

Opposing Ideal Current Sources

So I'm looking at the circuit below and a little confused by it. How are there two current sources facing opposite directions? What does this even mean and how can it be a valid circuit, since ...
0
votes
0answers
151 views

Constant current source array IC to use together with HT1632c LED driver chip

There's this HT1632 LED driver chip I want to build a LED screen driver circuit with and I want the LEDs to be bright so I cannot power the LEDs directly from the IC and need a current source for each ...
2
votes
1answer
70 views

Does it make sense to plot resistor current vs input voltage in this circuit?

simulate this circuit – Schematic created using CircuitLab I'm a bit confused by a question which asks me to plot current through R1 as a function of Vin using a constant voltage model ...
1
vote
1answer
140 views

7805 for 4-20mA current injector

I'm trying to setup a low cost current injector for testing certain I/O modules. I found a rather simple design for a current source using 7805. simulate this circuit – Schematic created ...
1
vote
3answers
79 views

voltage\current sources

I read in a book that image-1 is not a valid connection since you apply on the same two terminals a and b different voltages however image -2 is said to be a valid connection and I don't understand ...
0
votes
3answers
49 views

Why is output voltage being neglected when calculating power supplied by this current source?

If you look at the fourth equation, the example is attempting to calculate the power supplied by the current-controlled current source on the far right of the circuit. For the equation P = I * V, ...
0
votes
2answers
68 views

Direction of DAC output current

I am confused about the I/V Conversion at the output of this DAC (PCM1798) In the electrical characteristics section, a dc output current (called "Center Current") of -3.5 mA is given, for zero ...
3
votes
3answers
85 views

Leach circuit to power microcontroller

Like many, I'm trying to design small circuits to do things. One objective is a device to report home power use. Such a device is relatively easy. Powering such a device for the very long term is ...
1
vote
1answer
81 views

Can I drive all these FETs from this microcontroller?

I'm trying to design a driver for a 35x7 flip-dot display I picked up from scrap today. The plan is to put a half bridge at each column and row so at each pixel there's a full bridge. For this ...
4
votes
2answers
167 views

Generate current by microcontroller [closed]

I have to generate current values between 0mA to 110mA. Can I generate current automatically using a micro-controller? (For example: 20mA , 30mA...) I need to keep the current stable for ms in ...
1
vote
3answers
235 views

lm317 current source

I want to use LM317 to make a current source circuit for driving high power LEDs (500-700mA). The schematic in it's datasheet has no capacitor, but in some schematics there are one or two capacitors ...
1
vote
4answers
153 views

Using transistors to prevent short circuit / current limit

I am designing a circuit where I want to protect Q1 from current overload and popping in the event that Rl is a short. The length of wire in a short circuit situation is 0.7 ohms. Usually Rl is 10 ...
1
vote
1answer
177 views

How to use a current source with current control pin of LM13700

I am trying to bias the lm13700 Input amplitude bias current pin with a current source rather than using a voltage source and current limiting resistor as shown in all the data sheet schematics, but ...
0
votes
0answers
93 views

X-Ray tube Current Control based on PWM

I want a control module to be implemented in FPGA(Altera Cyclone IV running on NIOS2) using VHDL which controls current flow to a X-Ray tube. The scenario is I have the expected current value say ...
1
vote
2answers
126 views

30V adjustable current LED driver

I've recently started a project that has some pretty loose specifications. I need to develop an LED driver that can take an input of somewhere between 7.2 and 24V, and drive an LED panel at 30V with a ...