All Questions
Tagged with current-limiting transistors
38
questions
0
votes
1
answer
86
views
How to limit power to LED, efficiently
I am looking to use a 12V, 5 ampere car battery on a small 5V, 2A LED. Typical applications online use a resistor or voltage regulator, but since I am using a battery I would like to conserve power, ...
- 239
2
votes
2
answers
274
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LED Matrix to reduce current consumption
I'm trying to control RGB LEDs via USB. All LEDs have the same color, so I'm controlling them with only 3 PWM signals (generated from a PIC).
The problem I'm facing is to reduce the current needed in ...
- 23
0
votes
1
answer
434
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PNP Darlington pair as a current limiter
I am trying to analyse what is controlling the load current in the below Darlington configuration.
Is it the base current of transistor Q3 which is controlling current through R14 / emitter current ...
- 328
1
vote
5
answers
3k
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Current limit to 500mA (maximum) at 12V
I have a 12V DC output which can output 1A (maximum.)
I want a circuit that limits the current to maximum 500mA, so I don't accidentally draw more than 500mA as that would probably mean I have shorted ...
- 147
-2
votes
2
answers
736
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Current limiter using 2 bipolar junction transistors (BJTs)
I want to know where are the input and the output of this circuit in LTspice. I also need the values I should use for the resistors and the transistors in order to see clear results for current ...
- 1
1
vote
3
answers
311
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Is a base resistor always needed in a single transistor inverter circuit?
For the circuit shown, I'm trying to figure out if I need a base resistor or not.
What I'm looking to accomplish is a simple logic inverter to hold a power amp's active low shutdown at logic low ...
- 520
1
vote
4
answers
151
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Current limiting circuit operation
I cannot understand how this current limiting circuit works.
Image source: UNLV Physics Department, Bill O'Donnell, Current Limiter Circuit
Here is where I get confused:
When Q2 is turned on, the ...
0
votes
1
answer
203
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Constant current limiting circuit
Can someone help me understand the working of this circuit:
My questions :
Please explain me how this circuit will work in its entire operation range.
I am not able to understand the purpose of the ...
user220456
1
vote
1
answer
80
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LED strange behavior
I am analyzing ways to make a current limiting circuit, and here I'm having an unexpected problem. The schematic is as follows:
The problem I am encountering is twofold:
Even when node Vin is ...
- 31
2
votes
2
answers
1k
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Does a BJT optocoupler have an inherently short circuit proof output?
I want to use an NPN optocoupler (ACPL-214) to drive an offboard relay. I know how to size the input resistor to limit the LED current to 20mA. This will cause the output current to be in a certain ...
- 489
6
votes
1
answer
2k
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Using a depletion mode mosfet as a current limiting device
I have recently discovered the exciting world of depletion mode mosfets. Curiously, even in this document, I found nowhere that a depletion mode mosfet could be used as a current limiting/inrush ...
- 1,898
2
votes
2
answers
210
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Transistor Limit Current
I am using a LM395T transistor for an inductive load (a motor). The voltage limit is well within the 36V threshold. But current isn't limited. The specs of the transistor say that 1.5 A is maximum. ...
- 21
1
vote
1
answer
794
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How to limit current while almost keeping voltage same
I am supposed to design a power supply to a project. I have 3 alternative power supply designs for this purpose. However, one of them sucks huge current while giving enough current. My design is given ...
0
votes
1
answer
100
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Why does the high Side Current Shunt monitor fault as soon as power is on
The high side current shunt monitor fault goes high as soon as power is turned on preventing the P-MOSFET from turning on, its not faulting because of over current but as soon as the Enable signal ...
- 45
0
votes
2
answers
515
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NPN Transistor Current Limiting Changes From Collector Load To Emitter Load
as part of an audio project I've been working on, I've been measuring the current consumption of a class A amplifier driving a 4Ohm 5W speaker (square wave signal).
Strangely, I notice that this:
...
- 151