Scalable PSU/regulator GB

[AndrewT]

Hi,
would a series resistor after R4 junction feeding T1 emitter add a bit of current limiting in event of mishap?

[AndrewT]

Hi,
what is R2 doing?

Is it something to do with start up?

[infinia]

What are R3&R19 for? Isn't that a problem under transient conditions? They dominate the loop under turn on/off conditions.

[peranders]

Originally posted by BobEllis
I like the tripot idea.

Question for buyers: Do we want a trimpot in the parts kit or just a resistor that will give very close to 15V?

I ment both, both trimpot and 4 resistors. The extra trim resistors can be on top of the trimpot if it's necessary to save space. Trimpot _or_ triming resistors.

[JensRasmussen]

May I suggest soldering a resistor on the bottom side if extra trimming is needed

No point making a big problem out of nothing - IMHO

\Jens

[peranders]

Originally posted by peranders
C13, C15 why? Don't you loose feedback in high frequences?

Jens, you haven't commented this. Should the emitters of the differential pair be fed with a stiff current source and certainly not be decoupled?

[peranders]

Originally posted by JensRasmussen
May I suggest soldering a resistor on the bottom side if extra trimming is needed

No point making a big problem out of nothing - IMHO

\Jens

Jens, not a big problem really but I try to when it's possible to add optional parts because I don't like parts pacthed in here and there. Compare the work to fit in a LM431 if you thought of a LM329 in the first place. It's better to make a 4 pin part so both types will fit or simply have two footprints, one for the LM431 (and similar) and one for LM329 (or similar).

[JensRasmussen]

The 431 is out of the question as the voltage divider needed for low voltage references will raise the output impedance a lot (lower loop gain) I prefer the 10V LM4040 as this allows for a voltage divider with more gain compared to the 431 (2.5V) divider

The capacitor in parallel with the emitter resistor has been removed as I found it was not needed for stability. For practical reasons I have left it out as the cap needed to actually do any difference was so big (>100uF) that I chose not to bother

Initially I wanted it to be there as a gain reducer at high frequencies…. I found it to be not needed and removed it.

\Jens

[peranders]

Originally posted by JensRasmussen
The 431 is out of the question as the voltage divider needed for low voltage references will raise the output impedance a lot (lower loop gain)

Really? You set the reference voltage at the value you like (from 2.5 volts up to 35V) and set the gain according to taste.

Originally posted by JensRasmussen
The capacitor in parallel with the emitter resistor has been removed as I found it was not needed for stability. Initially I wanted it to be there as a gain reducer at high frequencies…. I found it to be not needed and removed it.[/B]

I think it is more like removing feedback at higher frequencies.

[JensRasmussen]

Originally posted by peranders
You set the reference voltage at the value you like (from 2.5 volts up to 35V) and set the gain according to taste.

Without the need for extra parts?

\Jens