Electronics > Projects, Designs, and Technical Stuff
LM317 digital control
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Maobuff:

--- Quote from: ZeTeX on May 20, 2016, 09:55:22 am ---
dont forget your bypass caps and protection diodes if needed.
R1 and R2 have a gain of 2, your buffer output goes instead of V2.

--- End quote ---
I get a new LM317T.
I used 249Ohm resistors. i get from 2 to 6.25V on adjust pin, and 3.25 to 7.5V on output. every thing is nice but I want to get output voltage as low as possible, any ways to do this?
ZeTeX:

--- Quote from: Maobuff on May 20, 2016, 12:42:04 pm ---
--- Quote from: ZeTeX on May 20, 2016, 09:55:22 am ---
dont forget your bypass caps and protection diodes if needed.
R1 and R2 have a gain of 2, your buffer output goes instead of V2.

--- End quote ---
I get a new LM317T.
I used 249Ohm resistors. i get from 2 to 6.25V on adjust pin, and 3.25 to 7.5V on output. every thing is nice but I want to get output voltage as low as possible, any ways to do this?

--- End quote ---
How low? if you want less then 1.25V you are going to need a very small current negative supply. there are many ways to generate a negative a supply. just google it.
Maobuff:

--- Quote from: ZeTeX on May 20, 2016, 02:19:09 pm ---How low? if you want less then 1.25V you are going to need a very small current negative supply. there are many ways to generate a negative a supply. just google it.

--- End quote ---
1.25V its fine for me
Maobuff:
I just breadboarded my previous design at its work perfectly. 1.25 to 6.25V on output.
ZeTeX:

--- Quote from: Maobuff on May 20, 2016, 04:17:29 pm ---I just breadboarded my previous design at its work perfectly. 1.25 to 6.25V on output.

--- End quote ---
Don't forget minimum load requirements (the circuit I posted covers that) , capacitors and protections. read very carefully the datasheet.
I don't think you need the op amp as a buffer because the adj pin is going to and internal op amp.
just because you got it working without minimum load does not mean it is stable, especially if this is your bench power supply you want to build it as stable as possible.
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