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 ...
2
votes
2answers
42 views
FET - Source follower utilizing current source to lower voltage offset
I understand that if I use a FET as a source follower, the signal will be slightly attenuated due to the fact that there is some small inherent resistance in the FET, creating a voltage divider effect ...
1
vote
2answers
66 views
Advice for my Voltage controlled Amplifier
In class we are designing a VCA together as part of a bigger circuit. The aim is that we have an input of speech and an input of music and when we speak the the music reduces in volume.
The speech ...
1
vote
1answer
48 views
Humming Sound of UPS vs DSP Inverter
I have a APC 1000VA BR Smart UPS.I have noted that the UPS Produces a Humming Sound when running on Battery Power.But my older a normal 500VA UPS(not from APC) seems to produce far lesser humming.The ...
1
vote
1answer
43 views
Calculating voltage in RLC circuit
Well I think the prof has made a mistake in one of his exercises, though asking here to be sure, The question is to calculate the supply voltage in the system below.
simulate this circuit ...
1
vote
1answer
59 views
What if there's current INTO an output pin?
maybe my question is easy to answer and maybe I shouldn't have asked it, but I'm really not sure.
I would like to connect an XBee ZigBee module (3.3 V) to a microcontroller (PIC, 5V) using the ...
4
votes
2answers
83 views
Bidirectional Current Source
I'm trying to design a bidirectional current source for the purpose of measuring very small (0.0001 Ohm) resistances. I've come across this circuit:
I can see that the transistors are there to ...
0
votes
2answers
53 views
Current and voltage sources
What happens when a current source is connected in series with a voltage source? I mean to ask, what will the current be through the series combination and voltage across it?
Is it allowed to make ...
1
vote
1answer
72 views
Very Simple Discrete Current Source
I'm trying to work out why someone would choose the right circuit over the left one. The only thing I can think of is, that one on the right can be made an adjustable current source by making \$R1\$ ...
1
vote
1answer
62 views
Source Transformation of dependent sources
Would it be correct to use use source transformation on a dependent source. For example, would it be legal to turn a voltage dependent voltage source in series with a resistor, into a voltage ...
1
vote
0answers
51 views
Equivalent Resistance
I'm working on the following homework problem. (Yes, this is homework. :p ) I'm supposed to find the current through L1 as a function of time.
simulate this circuit – Schematic created ...
1
vote
3answers
93 views
Does current source affect flow of current in circuit with a variable resistor?
Suppose you have a current source in series with a resistor R the current through the R resistor would be the current generated by the current source. How would the current through the circuit change ...
1
vote
3answers
207 views
Are there any way to get (75V 1A) output from 78V input
Is there any way to get 75 V 1 A output from 78 V input?
I found the TL783 high voltage adjustable regulator. But this can supply only 700mA output current.
I had forgot to tell the details.
Main ...
0
votes
1answer
54 views
Current source and resistor
If i have a current source and a resistor in parallel, i will have two nodes,if i ground the the node which faces in the direction of current of the current source will all the current flow to the ...
2
votes
2answers
139 views
How do I quantitatively describe a system with 2 parallel diodes and a current source
What would happen in this system? How can I find the bias point of a circuit like this:
Considering the LEDs are not perfectly matched. The 35mA are generated by a high precision stablizied current ...
3
votes
1answer
118 views
How to wire the REF200 IC for a 100uA current output?
I am trying to create a 100uA constant current source to power a homemade sensor. I bought a few REF200 ICs http://www.ti.com/lit/ds/sbvs020/sbvs020.pdf since each has two 100uA current sources. ...
1
vote
2answers
144 views
Input Resistance: Why can you ignore current sources?
This may be a weird question, but I simply can't figure out, why you can entirely ignore current sources when calculating the input resistance of circuits.
Here is an example (it's actually a ...
1
vote
2answers
91 views
Voltage between two terminals of an open circuit which's connected in series with a current source
simulate this circuit – Schematic created using CircuitLab
What will be the voltage between nodes A & B?
My guess is that the voltage between nodes A & B should be increasing ...
0
votes
1answer
142 views
Do you have to put a voltage across a PV cell for it to work?
I'm studying about PV cells and I'm slightly confused. Currently, I'm learning this very simple model.
I'm trying to figure out how exactly it works.
Am I correct in saying that; You apply a ...
0
votes
0answers
139 views
Constant Current Source ranging from 1mA to 1A (selectable) from battery from discrete parts and/or MCU
I am looking for a solution to get selectable constant DC current, range from 1 mA to 1 A, with output voltage limit as 800V DC, out of a battery, typically 12V, at the input.
What can be the best ...
1
vote
2answers
167 views
Cannot find efficient current/voltage regulator to power LEDs
I have a 12V 4-pin common-anode RGB PWM'd signal being used to power some LED strips, and I would like to use it to power the VL-H01RGB00302 Vollong 3W RGB High Power LED - which is basically a set of ...
2
votes
2answers
153 views
Is this electrical circuit solvable?
I am trying to solve a circuit with two current sources.
I1, I2, V1, V2 are known.
R1, R2, R3 are unknown.
I've tried node analysis, but I can only come up with two equations
\$\dfrac{V_2}{R_1} + ...
5
votes
2answers
211 views
Source and sink current
If I am connecting ICs to both sides of a led matrix, the ICs need to be able to source and sink enough current to light the LEDs? Or just sink?
Let me explain my question with an example:
In this ...
4
votes
2answers
151 views
How fast is the response time of a battery for a particular current demand?
If you demand a particular amperage, can the battery provide that amperage instantaneously or will it need some time to build up to that level?
I guess it will need time, but would like some ...
5
votes
1answer
399 views
How to build a voltage-controlled current sink / voltage-controlled resistor
I am trying to control a current through several current-mirror device (specifically the IREF pin on the TLC5940) using a single potentiometer. I've tried using a ...
0
votes
0answers
57 views
can power source damage electronics? [duplicate]
I think that this is a noob question but I just can't figure it out:
I have 2 devices :
First device working on 5V / 50A
Second device working on 5V/ 30A
I want to power them with power source : ...
3
votes
1answer
255 views
Temperature current source using a LM35
Anyone care to explain how this piece of circuit work?
I already build it and it works wonders but I can't figure it out.
4
votes
1answer
156 views
Measuring very small changes in resistor network using current source
I am trying measure a very small change in resistance (approximately .400 Ohms), due to the the effects of connecting a large resistance in parallel with a network of smaller resistors essentially ...
1
vote
1answer
296 views
Are these LEDs glowing due to leakage current? How to prevent it?
I've been trying to develop this circuit for a multiplexed display with two seven segment digits and five SMD LEDs. For simplicity, I've only shown one digit (LEDS 1 through 7) and two SMD LEDs (8 and ...
0
votes
1answer
273 views
Adjustable constant current source using a lm317
I am looking to provide constant current source, I am using a LM317 right now and it seems to be doing the job just fine. however I need to switch it between 2 or 3 different current levels. I can not ...
4
votes
2answers
175 views
buck converter for high current LED
My first question here:
I want to make a simple adjustable current supply for some LEDs I have (approx 3 V and up to 3 amps). I've decided against just using a single FET to control current as it ...
-6
votes
1answer
159 views
How to find the current and Resistance?
Ok Everyone DownVoted! i am sorry about the diagram! So i Updated it
this is my new diagram:
simulate this circuit – Schematic created using CircuitLab
Then Now how to find I1? what is ...
2
votes
2answers
153 views
Can a too powerful battery damage a circuit? [duplicate]
I have an IOIO board, a 13V 10A Battery (when I tested with my multimeter). For the IOIO board, 5-15V, ~10mA is enough. Can a 13V 10A Battery do wrong to the board or is it okay?
5
votes
4answers
725 views
Why does this current limiter circuit oscillate?
I'm trying to make a 0-25 mA current limiter. I want to take a control voltage of 0-5 V as input and have it control a current of 0-25 mA through a restive load (the restive load may vary between ...
0
votes
3answers
69 views
Finding source voltage, v1, and I1 in a circuit with a current source
simulate this circuit – Schematic created using CircuitLab
*Can anyone tell me why this circuit would be considered parallel instead of series?
2
votes
2answers
296 views
How does a real current source change its pd to keep constant current
An ideal current source is able to change its potential difference at the output to keep the same current at the output regardless of the load imepedance there. Real current sources are able to do ...
1
vote
1answer
79 views
Create circuit from current–voltage characteristic 2
Why is there a need for a current source in an electric circuit? As we know without voltage there will be no current flow then why do we call it current source? Why we do not use voltage in place of ...
0
votes
2answers
233 views
Format Approach to NODAL ANALYSIS
SITUATION:
Nodal Analysis is nothing more than applying KCL and is very powerful. I'm working on developing a more clearer perspective of two approaches in Nodal Analysis "GENERAL & FORMAT". Mesh ...
1
vote
1answer
226 views
How does current split in a circuit?
I'm redesigning a board that has a lot of peripherals attached to a SOC. These all use different voltages. Board is powered with 12V,1A
Most peripherals are connected like this:
RJ45 <-> GigE phy ...
3
votes
2answers
213 views
Sinking and Sourcing Current to and from a PIC24F Output Pin
Sinking and sourcing current refers to current going into and out of the MCU (respectively), right? If you configure a GPIO pin as an output, why would current ever go into the pin (since it's ...
1
vote
2answers
360 views
What do I need to build LED bulb
I'm thinking of using few of the CREE LEDs but wondering what all would i need to build
a bulb from scratch.
Here's what I've got:
LEDs (of course)
LED high current drivers
some sort of rectifier ...
6
votes
2answers
385 views
How should I select the resistors for this constant-current application for a 317?
Over at OnSemi, they have a little doc about using a 317 voltage-reg as a current source:
http://www.onsemi.com/pub_link/Collateral/AND8109-D.PDF
Their final example, providing constant current to an ...
4
votes
3answers
1k views
MOSFET - OPAMP circuit
I was looking for a voltage controlled current source see here , and I stumbled upon this circuit with description here :
Now I am having difficulty figuring out how this works - I made a model of ...
0
votes
1answer
155 views
When to use Nodal Anaylsis / Mesh / Superposition?
I'm studying these three methods and i'm confused on exactly which one is used when. This is a very broad question. Therefore, could some explain in general terms the difference of the three methods ...
0
votes
3answers
348 views
Node Analysis - current calculation
I have a cicuit here that's giving me trouble when finding out what V1 and V2 equal.The book says that I1 is traveling through the 8 ohm resistor (R1) towards ground. But when I build the circuit on ...
3
votes
2answers
832 views
Micro-controller controlled current source
I am trying to design a programmable current source that can go up to 5 A. I have a few designs in mind but none of them really seem to be best solution. I would appreciate if any one has any good ...
1
vote
1answer
94 views
KCL Node Analysis
I can do mesh analysis with KVL no problem however trying to switch over and to KCL with Node analysis I cannot understand.
How do you determine current coming in to the node? I don't understand how ...
0
votes
1answer
141 views
Circuit Simulator is being funky
This circuit simulator called "iCircuit" for mac users is showing some weird readings. It's showing a reading of 2.4mA and i'm getting 6mA in my calculations for this circuit I threw up. Am I missing ...
5
votes
2answers
104 views
BCR402R - what is the purpose of Rext in this LED driver?
I'd like to know what is(are) the purpose(s) of Rext in the BCR402R LE driver circuit.
The BCR402R is a 20 mA constant current LED driver. The application circuit (see below) shows an external ...
0
votes
0answers
59 views
iDAC + Current Mirror with 20V compliance
I want to create a 0-100uA constant current pulse with 20V compliance for use as portable biological stimulation device. I'm using a Cypres PSoC 3 as the MCU. I was originally planning to use an ...
5
votes
3answers
868 views
Constant current source
In my other topic i asked on how to create a sawtooth signal and guys on the forum gave me an excelent anwser. But! I cannot fully understand the first part of a circuit which is supposed to be an ...
