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Old 22nd March 2012, 01:00 AM   #1
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Location: Athens
Default Low Noise +-10V regulator

I ve been messing around with LTspice to learn how to simulate things, and I came up with this schematic.

It is meant to provide +-10V @250mA more or less with a rough Hfe estimate on the transistor, but I m still very weak at taking account current limiting, loading etc.

I had 4 sine voltages to simulate a 30V supply with ripple at various frequences. The output was pretty much very stable, although with similar parts, not the ones shown on this schematic.

Click the image to open in full size.

Any comments or suggestions are more than welcome. For the schematic or on how I can better simulate things on it.
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File Type: jpg d-reg.jpg (104.4 KB, 473 views)
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Old 22nd March 2012, 02:28 AM   #2
dangus is offline dangus  Canada
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So the transistors act as emitter-followers? Does Q2 have the emitter and collector swapped?

I'd take the easy way out and use an adjustable regulator like an LM317/337 or the LT improved versions, and add all the optional bypass caps. If it has to run from a wall-wart without a center tap, use an AC one and a 1/2 wave rectifier to get + and - rails. Maybe some RC filtering, or even an extra set of 3 terminal regulators to pre-regulate.
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Old 22nd March 2012, 03:30 AM   #3
Arius is offline Arius  United States
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Just use the TPS7A4901 and its complement. Beats the LM317/337 combo but current limited to 150mA. Suits your needs but you gotta be able to solder it.
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Old 22nd March 2012, 08:55 AM   #4
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dangus I think you are right... the pnp e and c are reversed...

About the other suggestions, I have tried most of them at some point, and they all depend on a heavy filtering topology, super silent rectifiers and other stuff that in the end make things more complicated and difficult.

The direct amplification of a super silent voltage reference seemed like a nice idea.

Their nominal noise output is at the range of -120db (with similar ripple rejection at low frequencies with minor filtering) while the usual suspects (317 etc) give -80db ripple rejection at best on higher frequencies with huge filtering.

I am not looking for an easy way out. I am looking to learn how to properly simulate stuff, and to design a super silent reg.
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Old 22nd March 2012, 07:23 PM   #5
AndrewT is offline AndrewT  Scotland
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I would expect the models of complex IC assemblies to be very approximate.

Using that information I would come to the conclusion that many simulations will predict results that in practice cannot be achieved.
regards Andrew T.
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Old 22nd March 2012, 07:48 PM   #6
Mooly is offline Mooly  United Kingdom
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Ripple isn't actually a sine wave. Try something like this altering the values to suit,
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File Type: jpg V3 +45 Volt Rail.JPG (74.5 KB, 169 views)
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