Better than lm317?

[cjdelphi]

When the lm317 is in current mode, the vdrop is maintained at 1.5vish volts..

Is there a chip which has an even lower voltage drop? Sub 1v?

 

[Harald Kapp]

USe your favorite search engine to find " low drop voltage regulators" (LDO).

 

[cjdelphi]

i was asking for personal experience. ... but yes i have looked

 

[cjdelphi]

Besides an ldo would not help i'm referring to the 1.5v drop across a resistor in current regulation not supply 4v higher in due to the forward drop

 

[Harald Kapp]

O.K., sorry, that wasn't clear to me from your post.

The voltage drop is given by the reference voltage that the regulator uses to set its output voltage (1.25V for the LM317 - that's what you should see across the resistor).
An LT3007, for example, has 600mV reference voltage, therefore it should be suitable for a constant current regulator with only 600mV voltage drop across the resistor defining the current.

And to anticipate the question: no, I have no personal experience with this chip.