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Discrete LDO regulator for 5v from 5.6v possible???

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micropar

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Hi all,

I am looking out for a discrete LDO (Low Drop Out) regulator circuit for 5v from 5.6v onwards using only discrete transistors, diodes or Op-Amps from readily available parts. Although LP2950 is available easily, but it can supply only 100mA. If you want more, out of luck!!!

Does anyone have an idea how to build one using only discrete components cheaply?

Thanks in advance,

Regards,
 

You don't mention the kind of current you need.

You could use an external pass transistor as shown on P16 of the LP2950 data sheet.

You could use another part or you could find an alternate part. It will simplify the PCB and possibly save money.

National has a bunch that go up to 1500mA:
**broken link removed**

Try Linear Tech
http://www.linear.com/pc/viewCategory.do?navId=H0,C1,C1003,C1040,C1055


TI:
**broken link removed**

Look at Micrel (micrel.com) as well. See MIC 5219
 

If you now that you have 5.6v in all the interval "I". Use a diode in serie. The diod forvard voltage is not current independent. But if you now what current interval you use then try some diffrent diods in that interval. Your 5v must have a +- something. 5v in USB is 5v+-0.25v...4.75-5.25.
 

Here ( picture attached, source unknown) is just a concept of a low-drop voltage regulator based on descrete components.
To increase current capability you will need to change several components, including pass-transistor, (you can use TIP2955 or similar) C1 (>1000µF) etc..
Regards,
IanP
 

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