3.3v and 5v regulator

Hi all,

I know it's kinda dumb to ask here that kind of questions but anyway :smiley:

Do you know any good and simple Transistors (circuits) for 3.3v regulator and 5v ?

Input voltage about 20, 15, 10v (2, 4, 8 A) and Out put 3.3v and 5v, Out I about 1, 2A ?

I wanna make a circuit and put 3.3v for the modules that need 3.3 and 5v..etc

Do you know any good and simple Transistors (circuits) for 3.3v regulator and 5v ?

Why a circuit? Why not a three pin regulator? Or do you want a switching regulator?

I will build a main circuit which gonna have both 3.3v and 5v in the same circuit and gonna make lines which module, chip to take from 3.3 or 5v

That doesn’t answer my question. You just include two three pin regulators, these will make a much better regulator than a 10 transistor circuit. Look at the equivalent circuit in the regulator’s data sheet.

If you mean as i understand just 3 pins transistor regulator yea that would be fine but which
transistors should i choose ? or wait do you mean the regulators that arduino boards use? the smd ones?

A regulator is not a transistor, it is made of many transistors and resistors on one chip.

Input voltage about 20, 15, 10v (2, 4, 8 A) and Out put 3.3v and 5v, Out I about 1, 2A ?

What is the maximum input voltage? What is the maximum output current?
For 2A load with a large voltage drop a switch mode regulator (dc-dc converter) is
a much better choice than a linear regulator, as lots of power will be wasted in
a linear regulator.

What is the maximum input voltage? What is the maximum output current?

Max Input voltate: 20v, Max output current: 1A or 2A , Output voltage: 3.3v

I don't need to switch between the regulators.

I just need a type of transistor that gonna connect a battery in the input and output to get 3.3v
and another for 5v.

I need type of transistors and circuits if possible.

So 2A is your max output current yes?

For the components that I use i don't think they gonna draw more than 2A so yes.

Then one of these is probably a good match: 10pcs Dc-dc Lm2596 Converter Buck Adjustable Step Down Power Module 1.5 O5t4 for sale online | eBay

Use that to get to 5V, then a high current linear regulator for the 3V3 (probably needs a heat sink).

Or two of those units, one for each rail (they are ridiculously cheap really)

Hehe thanks for the info MarkT I have one of that but i need to put in my own cycruit a 3.3v
and a 5v regulator.

I remember some Transistors but need to search them.

I'm building a circuit for example like arduino Uno..etc and i wanna put on board a 3.3v and a 5v outputs
I need some kind of transistors that will change the voltage from a single battery Input and get as output
5v and the 2nd transisotr (regulator ) 3.3v

Domino60:
I don't need to switch between the regulators.

No.

A switching regulator is a method of making a regulator that is much more efficient than the linear regulators you are looking at. And better efficiency equals less heat to get rid of in the components.

A switching regulator is a method of making a regulator that is much more efficient than the linear regulators you are looking at. And better efficiency equals less heat to get rid of in the components.

I didn't knew about that, is there any kind of circuit you can saw me?

I would recommend that you buy a ready built module because a schematic is the least of it. It is difficult to get these circuits stable and you need a printed circuit board and a well designed layout. I have had engineers working for me that were specialists in this sort of circuit and none of them got it right first time. The modules themselves are not expensive.

I think i will stay at linear voltage regulator, you know the transistors with few caps will do the job for my
circuit. Found L7805CV, LM2940 for 5v and LM1117 for 3.3v, do you know any other for 3.3v ?

Might be a couple out there:

A lineair regulator is NOT ok for this job.
20volt in and 5volt out is 15volt difference. That, with 2A current draw, generates 30watt of heat.
You would need an 7805, driving a second bigger transistor. And a 10x5x5cm heatsink that runs stinking hot.

A $3 switching regulator does this without, or with a very small heatsink.

Going from 5volt to 3.3volt is only 1.7volt difference.
Much easier for a lineair regulator.
Standard 1117 regulators top at 800mA.
If you want more current, it might be wise to look at the Pololu website for a 3.3volt buck regulator.
Leo..

CrossRoads Nice website

I don't know anything about swithing regulators, can you give me some info and circuit Wawa?

A lineair regulator and a switching/switchmode/buck regulator do the same thing. Lower the voltage.
They just do it in a different way.

The main element in a lineair regulator is a pass transistor.
Because the voltage difference between input and output is across the transistor, it gets hot when current is drawn.
Power (heat) generated in the transistor is voltage difference times current.

A switching regulator uses a switch (mosfet) as pass element. A switch is basically lossless.

A switching regulator uses an inductor to store/release energy.
The switch is "on" for a short time, and "off" for a longer time.
Therefore input current is lower than output current.
e.g. 5volt/2A out only uses 0.6A from your 20volt supply.

There are also switching boost converters, that increase the input voltage.

Some things have been left out for clarity. Google e.g. "buck converter" for more info.
Leo..

do you know any other for 3.3v ?

LM232 - 3A
MC33269
LD1117#33
LD2980ABM33TR
LD2980ABU33TR
LD2980CM33TR

LD1085#33

LM2931AD33R