Why 7805 is better than LM1085?

[peranders]

Elso, you can improve your 431 regulator. Let R5 be connected to the output. Then you will get a precision voltage. I have used it often when I have wanted a precision 5.00 V reference AND supply voltage (microcontroller with ADC).

A "tripleton" isn't neccessary, a Darlington will do if you have feedback from output.

[peranders]

Elso, i didn't read too carefully but why didn't you use global feedback? 431 is a very reliable and stable chip. It has never failed for me, never got broken. I have used around 50000 and they simply work! Not all of them are in the "power" configuration but rather many.

The big advantage is the surprisingly dynamic impedance. Good for surpressing incoming noise.

[Elso Kwak]

Hi peranders,
If you read my post carefully you will notice I tried your suggestion already. In fact this was one of the first things I tried. We don't need a "precision" 5 V for the TDA1543. It also works on 8V. 5.08 V is accurate enough. I choose to make a non-feedback circuit to avoid oscillation and HF garbage from the TDA1543 entering the regulator circuit as much as possible. Triple Darlington or simple two transistor Darlington is not a big difference though. That's why I stopped at three. Did you know Audionote has five transistors Darlington connected in the Audionote DAC3 supply?. Thanks again Jean-Paul for a copy of the schematic!

[peranders]

Originally posted by Elso Kwak
We don't need a "precision" 5 V for the TDA1543. It also works on 8V. 5.08 V is accurate enough.

I used this circuit mainly to reduce cost in my MCU application. 431 is very worth the price. I don't know if there is any better reference?

431 can oscillate accordning to the datasheet but my experience is that the chip isn't so sensitive in real life. It can take much RF-emission too. I have had very good experience with CE testing. Never been to a trouble.

[Elso Kwak]

Hi Peranders,
I was more worried about emittor follower oscillations than the TL431 as the latter is in its stable region.

[peranders]

Originally posted by Elso Kwak
Did you know Audionote has five transistors Darlington connected in the Audionote DAC3 supply?. Thanks again Jean-Paul for a copy of the schematic!

Can this really be good?

Leakage from the first approx. 50 nA x 300 x 300 x 300 x 300 = 405 A

Hfe 50 => 300 mA

Leakage 10 nA, Hfe 100 => 1 A

Isn't this a VERY sensitive circuit? Very small leakage generates VERY much current which you don't can control.

Am I wrong?

[Fred Dieckmann]

Probably you are probably wrong............ I have no idea what you are talking about from your collection of numbers without a clue as to what they are supposed to represent.

Leakage of what?
50 nA x 300 x 300 x 300 x 300 = 405 A!!!????

Thanks again for your insightful input to the forum.

BTW When using a darligton follower load each follower with a resistor to ground to set a quiesent current for each follower stage. This is neccesary to get a decent Hfe out of each follower stage and will also make each stage operate Class A.

[Elso Kwak]

Hi peranders,
I don't know where you got these leakage numbers from and it may escaped your attention but my circuit is a <B>working</B> one!
Audionote uses 680 Ohm resistors from bases to ground in the last four transistors as also Guido Tent does. I just edited in Guido is using 470 Ohm. I will not post the Audionote schematic but Guido's is very similar and can be found here:
http://members.chello.nl/%7Em.heijli...html/suplv.pdf

Hi Fred,
I considered fitting these resistors too as you suggested but as the circuit worked quite satisfactory I stopped adding parts. Remember the "partsfarm"?

[Elso Kwak]

Hi Fred,
I just tried it with 680 Ohm resistors from the bases of the Q2 & Q3 to ground. Outputvoltage is slightly lower: 4.75 V but sound is the same. Sonically no improvement. Thanks anyway, Fred.

[peranders]

Originally posted by Fred Dieckmann
Leakage of what?
50 nA x 300 x 300 x 300 x 300 = 405 A!!!????

Thanks again for your insightful input to the forum.

Fred, you know about leakage current in transistors?

I wonder of the benefits of a "quadrupleton".

Besides, Fred, can't _you_ come with some insightful input instead of just complaining?