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-   -   Replacements reg´s circuits L7805 - Help. (http://www.diyaudio.com/forums/power-supplies/189931-replacements-reg-s-circuits-l7805-help.html)

matiasro 30th May 2011 02:17 PM

Replacements reg´s circuits L7805 - Help.
 
Hello my friends.
I'm writing from Argentina. I ask for help. I want to build a low noise regulator to replace a L7805. Not fluent in English and that makes clear what I read in this forum. The intention is to build, not buying a super regulator.
Someone can help me get a low-noise circuit to replace my current regulator?
The current requirement is 200mA.
Thanks my friends!
Matias

nightanole 30th May 2011 02:33 PM

PCB for teddy's 'Regulator booster' - pink fish media

Not sure if this can handle 200ma, but it can handle well over 100ma. Its a drop in replacement. You just make the simple circuit, and plug it in where your 78XX used to be.

Chris Daly 30th May 2011 02:44 PM

Hi
For a positive supply Use a common collector NPN transistor regulator, with two resistors between the collector and base, midway between these resistors use a 2.2uf cap observing its correct current for a 1 watt zener of 5.6v. for 12volt supply use 2x 15 ohm resistors between the collector and base , choose a transistor suiting the current requirements. Between the base and ground parallel with the diode use another 2.2uf cap. This will then have a very low ripple output.


A BD139 has quite a bit more current than 200ma but can be used with some series resistance on its output if needed if you have a specific 200ma requirement.

The emitter then - its output of the BD139 should be very close to 5volt for a 12 volt input. Its very late here in Australia, but I can draw a schematic tomorrow.

Cheers / Chris

Andy5112405 30th May 2011 03:19 PM

Hi

For low noise try using an LM317 it is an adjustable regulator butis much lower noise than the 7805. It uses the same component count as the 7805 plus two resistors. It comes in various guises with varying output current capabilities and is cheap.

! 30th May 2011 09:42 PM

There are hundreds if not thousands of ICs that can give 5V output @ 200mA with only a few additional parts and do it with same or lower noise than LM7805. Check your local electronics distributor, there are so many they won't even know where to start suggesting them unless you come up with more criteria than just 5V, low noise, and 200mA.

Chris Daly 30th May 2011 11:37 PM

1 Attachment(s)
Transistor based common Collector assumes 12v in as the voltage source and provides 5v
output. Schematic below, please post a reply to tell us if it was successful

Hope this helps / Chris


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