| janneman |
Elso, we missed you on DDIY2004! (I know).
On the Bongiorno thing, I have no idea what he is talking about. His post is almost content-empty, which doesn't help either. Of course, 'rock steady' and 'dead quiet' are not easily verified in engineering terms...
Jan Didden |
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| Steve Eddy |
| quote: | Originally posted by Elso Kwak
Hi, I came upon this post by James Bongiorno. A powersupply regulator with only two transistors. "Positive feedback"? Anyone has an idea what this might be???
http://groups.yahoo.com/group/SAE_Talk/message/7561
:confused: |
Geez, you have to have a user ID and password just to read a message there?
se |
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| Elso Kwak |
| quote: | Originally posted by Steve Eddy
Geez, you have to have a user ID and password just to read a message there?
se |
Seems to be so. Here is the message:| quote: |
From: James Bongiorno <sstinc@e...>
Date: Tue Apr 20, 2004 5:30 pm
Subject: Re: [SAE_Talk] ATI Amps
Thanks for the compliment. Actually, that IC regulator in the Thaedra was quite
unique. I have since (after about 30 years) come up with something even better
which is in my Trinaural Processor and will be extensively used in my new
Ambrosia. I call it my "positive" feedback regulator. It's a real gem and very
simple. It is dead quiet and is as stable as a rock and only uses TWO
transistors. Enough for now.
James Bongiorno |
:cool: |
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| slowhands |
I am always skeptical of radical claims in this field.
Bongiorno is a genius, technically and as a huckster. I fear this one is more marketing blarney than technical breakthrough. |
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| Ouroboros |
Well you can make a pretty reasonable fixed output LDO regulator with only two transistors, but you do seem some zeners!
The general arrangement shown below works. |
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| Ouroboros |
| The regulator in my drawing outputs 36V (or near enough) |
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| demons_wing |
| how does it work?...almost looks like a switch. you will have to forgive my ignorance...my electronics is poor :) |
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| Ouroboros |
Zener Z1 sets a 10V reference at the base of T2.
Initially the output of the regulator is at 0v. The emitter of T2 is low so T2 is on, and current flows through T2 to pull the gate of the P-ch FET T1 down, so that current flows to the output. As the output rises, then at approx Vout = 36v then the emitter of T2 will approach the base voltage, slowly turning T2 off. This in turn starts to turn off T1 in a negative feedback loop, keeping the output regulated.
Vout = V(Z1) + V(Z2) - Vbe(T2). Or near enough.
The Cg-s of the FET is enough to keep it stable, but you normally need another zener (10v or so) across G-S of the FET to prevent Vg-s from getting too high. |
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| Bricolo |
If it's the same as Ouroboros schematic, I don't see were the positive feedback is
And what is so good about positive feedback? |
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| Ouroboros |
| I'm not saying my regulator is the same. It's just a simple two-transistor LDO that works well. (Just as a comparison) |
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| Elso Kwak |
Hi, I can imagine two possibilities:
1. Darlington connected,
2. Sziklai (complementary Darlington).
Both with a reference or zener at the base. To call the Sziklai positive feedback I am not sure.....:confused: |
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| janneman |
| quote: | Originally posted by slowhands
I am always skeptical of radical claims in this field.
Bongiorno is a genius, technically and as a huckster. I fear this one is more marketing blarney than technical breakthrough. |
Also note that he puts "positive" between quotes. I wouldn't hold my breath for that breakthrough.
Jan Didden |
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| Steven |
I have no idea how it works, but a combined positive and negative regulator looks like the right hand side of this photo. Just not big enough to see the details.
Steven |
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| boholm |
Does this qualify for a two transistor PSU?
P.S.: Don't get too hooked on the values. This was just a test to see if it could work - and it can. |
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| Ouroboros |
| Yes, but it really needs a zener to provide a reference voltage in series with the emitter lead of the lower transistor. |
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| lumanauw |
Hi, Steven,
I like this very much.| quote: | | The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973 |
I also think analog is kind of "Art" while digitals are "Exact science" |
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| janneman |
| quote: | Originally posted by lumanauw
Hi, Steven,
I like this very much.
I also think analog is kind of "Art" while digitals are "Exact science" |
The way I see it, successfull design, whether analog or digital, is the art of optimum choice in trade-offs and compromises. It's all art in the end.
Jan Didden |
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| djk |
"Yes, but it really needs a zener to provide a reference voltage in series with the emitter lead of the lower transistor."
Why?
NAD use this type of regulator without a zener. |
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| Ouroboros |
| quote: | Originally posted by djk
"Yes, but it really needs a zener to provide a reference voltage in series with the emitter lead of the lower transistor."
Why?
NAD use this type of regulator without a zener. |
Sure it'll work as a bodge job, but the temperature stability of the output is atrocious if you only use the Vbe of the sense transistor as the voltage reference. (just Spice it and look at the temperature plots) |
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| destroyer X |
I know this is not only 2 transistors..... each side at leat tree...but, as i am using 33 years long, and i construct more than a hundred to friends use their 20 Amperes consumption SSB Radio Transmitters (consumption moves from miliamperes to 20 amperes in a matter of some microseconds) that i decided to show you.
A lot off supplies is almost this one.... the difference is that one is tested a lot, long time testing... some users died and his son is melting strong wires only to joke.... only to see it melt making output short circuit.
Do not answer your question.... but i send it to say you hello... also boholm and other friends.
Carlos
Carlos |
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| john curl |
| This last schematic is representative of what a '2 transistor' regulator would normally look like. This was the original design for dc regulators in the '50's and '60's. Many early transistor design textbooks have this model. |
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| johnnyx |
One of the transistors could be used as a zener, the reverse breakdown voltage of the base - emitter junction is about 6 to 7 volts. If the current is limited to a few mA, then it can be used as a zener substitute. (this is why the max voltage for TTL is specified as 6V, and why the max reverse VBE is 5V in most transistor data sheets.)
It's a noisy one though, I've seen it used as a white noise source, compared to a band - gap reference. Just like all zeners above about 5V, they are really "avalanche breakdowns", and this is a noisy process.:( |
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