L'Amp: A simple SIT Amp

[luvdunhill]

How much current flows through the bias supply? I'm curious about power dissipation on the regulator?

 

[Michael Rothacher]

It depends on your SIT, but it's tiny i.e. microamps. You don't really need to go crazy (unless you want to).

 

[Zen Mod]

20 to 30A is 'nuff

not exactly enough for welding , but almost .......

 

[Michael Rothacher]

Naughty.

 

[Zen Mod]

ok

just add m after 20 ...... and ignore the rest

(besides ...... every proper Greedy Boy is already thought to ignore tech part of my posts ... if not all parts )

 

[luvdunhill]

ok

just add m after 20 ...... and ignore the rest

(besides ...... every proper Greedy Boy is already thought to ignore tech part of my posts ... if not all parts )

I see. LM317L then okay? (TO-92 regulator)

 

[Zen Mod]

certainly
even if I know that Papa would say that plain RC based net is good enough .....

 

[Michael Rothacher]

Cap/Zener too.

Nothing with a long TC.

Of course, the schematic I posted at the beginning of this thread is proven to work well, so maybe that will be of interest.

 

[Franz Gysi]

Cap/Zener too.

Zeners are noisy, but in this application with such a little gain should not be a problem...

Franz

 

[Zen Mod]

then LEDs instead of zener

 

[Michael Rothacher]

Zeners are noisy

Hence Cap.

Like I said, I've posted a schematic for a proven solution at the beginning of this thread.

 

[Michael Rothacher]

Mike R,
I use the 15R lowthers...

Hello Mike,

I'll post some info for you when I get home, but you may want to peek at Post #23 for now.

 

[Zen Mod]

..... proven solution ....

that's in MR's nature

 

[Michael Rothacher]

I have to actually build this stuff. I'm way too dumb to do it in my head.

BTW, I confess I'm greedy; I totally fell for your F5 Turbo schematic.

 

[Zen Mod]

would you believe me , if I say that that's really what Papa sent me , as reply to my own greed ?

 

[Salas]

o-k- with your CCS the hum was really absent...

I am still not happy with so much wattage in resistors......

so I am open to try another CCS solution, really!

Here is a plain one, though not that bad, in case you will need it. (Q3's drain is pointing ''north'' in the schematic, you may use one red or green LED on top of Q3 in series if you wanna know the thing is ''on'' at a glance).

 

[ra7]

Thanks Salas! This one is similar to the original Zen. What is the purpose of 2sk170 in this CCS?

 

[Salas]

Ups the PSRR a lot by keeping steady current through the PNP controller transistor.

 

[Zen Mod]

instead of 2SK , maybe is BF245A adequate for cheapskates as us ?

 

[Salas]

Of course. Degenerate for about 2mA through the BC560B.