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Hi all, I'm trying to build an adjustable voltage regulator using the TL783. I have brought an LM317 into my circuit and am attempting to edit it's values so it functions as a TL783. However, as I'm not very experienced, I am having trouble ascertaining certain values using the TL783 datasheet. My main concerns are, Adjustment Terminal Current (I_ADJ), Adjustment Terminal Impedance (R_ADJ) and Output Impedance (R_O) Could somebody guide me as to how I would interpret these values from the datasheet ? http://www.ti.com/lit/ds/symlink/tl783.pdf Many Thanks

I_ADJ is the current flowing out of the Adjustment pin:

ADJ input current in the datasheet.

R_ADJ is a strange parameter that CL seems to have added to their model but which bears no clear relationship to anything inside a real regulator.

R_O appears to be an attempt to represent the internal series pass element output resistance, however, for whatever reason (CL don't release their models so it's anyone's guess what the subcircuit looks like and so where R_O actually is) the default value of R_O is set way too high.

Basically to make the model give decent regulation you need to reduce R_ADJ to the nanoOhm and R_O to the milliohm range.

This thread has some background about the R_ADJ and the R_O values:

https://www.circuitlab.com/forums/support/topic/ffgw6682/lm317-does-not-regulate/

Many Thanks for your answer. I think it's going to be difficult to get a realistic simulation from the circuit then.