advertisement


The best regulator I've built so far

Hi does anyone have a couple of 33uf 35V tants they could sell me so that I could build a couple of the regs. I was hoping to build these quite soon and would prefer not to have to order from the USA. Please PM me.

Cheers,

Ian
 
Hi,

I am thinking of making a few of the fetlington TedyRegs™ to power the DAC chips and input receiver in my digital crossover, one reg per component. As none of the components are very high current (or voltage), do I really need such a high current output transistor as the D44H11? If not, maybe someone could suggest a nice replacement that is more cost friendly? In fact I have a load of BD139, would they work?

I only want 5.3v under load (I swear it sounds better than exactly 5v!), so around 5.6v unloaded. Am I right that R1=3K4 & R2=455R will give me this, keeping R4 in place?

I read the whole thread but it is pretty intensive reading so I went a bit comatose! I seem to remember someone saying the fetlington implementation was not very accurate at getting the exact voltage?

Thanks!

Oh, can C4 be 30uF or does it need to be exactly 33uF?
 
Hi I think I must have got something wrong. I have just built a negative version of the regulator. I have used a FET 2N5461G for T1 (drain=collector, base= gate, emitter =source) T2 is a D45H11. The circuit followed was as Teddy showed in post 1 but obviously I used a LM337 instead of 317 and the 0v rale was positive with repsect to theoutput of the regulator.

I checked the voltage out of the LM337 as compared to the output of the whole circuit (I expected a volyage drop of maybe 4-5) instead I get a drop of about 0.5V (11.9v to 11.4v). Will this be correct or is there a likely error?

Cheers,
Ian
 
Hi I Did print the data sheet to get the FET right, ( I will check again) so I think it is ok. Am I correct that I have interpreted the circuit correctly?

Cheers,

Ian
 
fatmarley said:
Bugger! Just made a 5v fetlington and i'm getting 6.5v out. I'm using 1k for R1, 150R for R2 and 330k for R4. T1 is a 2N3819 and T2 is a D44H11. Does that sound ok? . . I tested it in my Rega ear headphone amp. The raw supply after the main caps is 36v dc. The amp should run on 24v after the regulator but im putting what should be 5v (the multimeter is reading 6.5v) into it for testing. Will i get an accurate reading using the headphone amp as a dummy load?
Click to expand...

I also just built my first 5V fetlington based on the circuit posted by Teddy, around page 3 IIRC.

I used the same part values he suggested, only I used different values for the resistive divider on the LM317 to get a lower voltage. 2SK117 & D44H11 used.

Anyway, Teddy said to expect a 5V drop with R4=330K which is what I am using, but I only seem to get a 1.1V drop between the 317 output and the main output from the D44H11.

I used a pot on the 317 so I can vary the voltage to make it output 5V, but is it even regulating properly if I am only getting a 1.1V drop when I was told to expect 5v?

Some advice please! :)
 
Hi,

With FET thansistors the dropout rules are a bit different... and it depends on the transistor you use. The voltage at the FET output may be higher than it's input. Just change the restitors to get the voltage you need
 
Hi thanks Teddy. I used the 2SK117 as you suggested along with the D44H11.

Would you recommend I change R4 to give me a bigger drop-out or just reduce the voltage from the LM317? Reducing the voltage from the LM317 seems to make more sense but I did notice you said somewhere that having the larger drop-out makes it sound better.
 
The dropout will vary according to the suffix of the 2SK117 there are GR, BL, etc.

From heat dissipation perspective it's better to have the dropout around fifty fifty between the 317 and the D44H11. Otherwise, as long as you have some dropout on the transistor you're OK.
 
Hi in my first attempt at the negative fetlington using a 2N5461G I found only 0.5V drop (Fet definitely in correctly). I was unhappy and converted it to a darlington using a ZTX751 I had kicking around and found the V drop across the VBE increased to about 3.5V.

After messing around I found the V out varied if the VBE was put under load (the change apprears constant under different loads) is that normal?

Additionally the Vdrop across the VBE alters with input voltage, making the use of a pot on the LM337 almost manditory, again is that normal?

Ian
 
The voltage drop difference between no load and under load sould be around 0.5V. If you have much more than that there's probably something wrong. Check that the collector of the D44H11 is connected to the output of the 317
 
Thanks for that Teddy, the voltage drop is see is 0.25V, which sounds good to me. The voltage drop on load certainly confirms my view that to use these regs on low voltage devices like DACs, a trimmer must be used to set the final output voltage. Not sure what some 5V devices would make of a 10% drop in supply voltage.

I will try the regs on my DAC as soon as I can get a chance.
 
Is it possible to post here the last version of the schematic diagram with a parts list? If available please also the schematic and the list of a V- version. With the many modifications I lost the overview totally.

Thanks

Peter
 
IDM - There's a simpler solution than a trimmer. When there's no load at all, there's no current through the D44H11, and thus no dropout. As soon as you connect a minimal load there's 0.5V dropout. From this point on the dropout will change very little with the load. If you don't want to see a dropout change, you can simply connect a 1K resistor at the VBE output.

p.st - I'll try to find a free moment and start a new "clean" thread with "howto" instructions.
 
Hi guys, I have bought a bag of the 2SK117-GR and if anyone needs a couple of these fellows, drop me a PM.
 
You must log in or register to reply here.


advertisement


Back
Top