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help for making simple for decresing 12v dc to 3.7 volt dc

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shahidsiddiq8

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12v to 3.7v

sir if we use 18 ohm resistor then according to ohm law
i=v/r
i=12/18=666.6ma
when i give 666.6ma to base of bc 337 npn transistors it push collector and current goes collector to emitter are 66660 ma according to transistors rule (one electron in base push 100 electron of collector)
why i need only 600 ma and 3.7 volt from emitter (bc 337 npn transistor)
u can help me with formulas for solving this project


thanx
 

3.7 volt regulator

Look at the datasheet for a BC337 transistor. I looked at the one by Philips.
The max allowed peak base current for a BC337 transistor is 200mA. You will destroy it with 666mA.

Its max allowed collector current is 500mA and for it to saturate well its base current should be 50mA.

If you are using the BC337 transistor as a linear voltage dropping resistor then if there is any load current the transistor will get too hot.

How much load current at 3.7V do you need?
 

12v to 3.7 volt resistor need

sir i need 3.7volt dc with 500 ma current
kindly send me circuit diagram used a zener diod and resistors and one bc337 npn transistor with calculation formulas


thanx and regards
 

4.4 volt zener diode

shahidsiddiq8 said:
I need 3.7volt dc with 500mA current
kindly send me circuit diagram used a zener diode and resistors and one bc337 npn transistor with calculation formulas
Click to expand...
The voltage across the BC337 is 12V - 3.7V= 8.3V.
The current through the BC337 is 500mA plus maybe 10mA for the zener diode.
Therefore the power in the BC337 is 8.3V x 510mA= 4.2W which will cause it to overheat and probably melt.

This is a linear voltage regulator that makes a lot of heat. A power transistor is needed that is mounted on a pretty big heatsink.
The voltage of the zener diode must be 3.7V plus the base-emitter voltage of the transistor for a total of about 4.4V. Nobody makes a 4.4V zener diode.

Use an LM317 adjustable voltage regulator instead.
 

circuit dc 12 v to 3.7 v

Hai shahidsiddiq8
You may ise the given circuit which uses only one LM317 and is capable of varying between any voltage from 1.2v to 27 volts when fed with 30 volts DC and up to 1.5 Ampheres as per its datasheet says. In my practical experiences, i have used the same circuit to draw up to 1 Ampheres. But do use a good heat sink. In your case feed 12 volts and adjust the 2K variable resistor to get the desires voltage at the output. Hope it helps you.
 

bc337 12 volt to 5 volt

The more expensive LM117 can use a resistor value as high as 240 ohms from the output to the ADJ terminal. The LM317 needs a resistor that is no higher than 120 ohms or some of them will have the output voltage rise when there is no load.

Then the value of the 2k pot will need to be reduced.
 

simple 12v dc to 9 v dc circuit

This LM is piece of crap he disipate to much.
Better use real pow supply with transistors like this one:
 

12v to 3.7 v power regulator

Both solutions are simple (low component count) linear supply solutions. Power dissipations should be on similar level.
 
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