How do I Fine tune a 78L05 ?

[Dimbulb]

base to ground is 3.071 V
ground to emitter is 2.510 V

I think I need to re wire the transistor
one moment please

Chris: yes I begin: http://ffden-2.phys.uaf.edu/212_fall200 ... solid.shtm

my final attempt tonight after rewire was the same.
one final trial was adding 5k impedance raise the 2.5 to 3.14 an improvement

[rshayes]

You should have a voltage divider from the emitter of the transistor to the adjustment terminal of the TL431. Basically, a 10K resistor from the transistor emitter to the adjustment terminal, and a second 10K from the adjustment terminal to ground.

The adjustment terminal will be at 2.5 volts, the emmiter should be 5.00 volts and the base should be in the 5.6 to 5.7 range.

[MrAl]

Hi there,

Just wondering, did the origainal poster state what kind of application
this was going to be used with...why the super accuracy...

[Dave Dixon]

So Dimbulb, Did you check out that website with the info on your meter? It looked really helpful (In general - not for this specific project). Dave

[Dimbulb]

thankyou I downloaded the manuals.


the application:
the application 100mA 5.000 V from a 9 volt battery, it is a supply for hobbiest that need a little more precision. some future improvements include a pre-regulator. Also getting a little more life from a 9 Volt battery.

since most regulators take care of 99% of projects this power supply is for the 1% that go beyond.

[Dimbulb]

The regulator is working !
After a night's sleep I re- read the last post.

I removed the 10k resistor from the cathode of the LM431 and soldered it to the emitter the results are no drift 5.028 V

I am very pleased with this circuit. The quiesent current of 4.85 mA

I have mounted new parts on a pcb, testing gives a max output of 30mA with a single 2N4401.

I appreciate your help very much!