Linear regulator (LT1084,LT1083,LM338, )

yunwt

Member
2015-07-19 3:04 pm
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This might be of help. LD1084 with ground plain and t bar between main caps. Not bad really. LM317 as good if 2.2 A type. I have a LM324 and BC327 ( ? collector to V+ ) as crow bar to V set. Makes it jump down to 2.5 V ( LM324 + Vce loss X Vref ). Note last graph switched off. Ignore red wrighting. Te scope is set at 1V ref. Add 21.5 dB @ 12V. - 130 db is realistic for preamp use.
 
Is this one you have designed and built yourself ?

Hi Mooly,
No this one is from ebay.
Here is the link

LM317 350 LT1083 1085 LOW Noise Adjustable Linear Regulated Power PCB Soft Star | eBay
And I have some serious reservations against this circuit. However I did buy 4 boards to modify and use instead.

My reservations are mainly on the series resistors R1, R2 ad R3. They are supposed to be current limiting?
But the value like R3, if we use 2.2A current 5W is dropped across the resistor. But why?
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
My reservations are mainly on the series resistors R1, R2 ad R3. They are supposed to be current limiting?
But the value like R3, if we use 2.2A current 5W is dropped across the resistor. But why?

Just reading through the notes and it seems that R3 can be in the 0.1 to 10 ohm range. I guess that leaves it up to the user to decide the most appropriate values.
 

Gusser

Member
2014-02-20 9:52 pm
I see an issue with the design.

The output fuse will drop voltage. Therfore it should be within the sense loop. Otherwise you will have poor load regulation.

However most IC regulators are well protected against shorts and over current. the output fuse is not necessary. I would just bypass it with #14 wire.