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
http://groups.yahoo.com/group/SAE_Talk/message/7561
Elso Kwak said: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
Geez, you have to have a user ID and password just to read a message there?
se
Re: Re: To good to be true?
Seems to be so. Here is the message:Steve Eddy said:
Geez, you have to have a user ID and password just to read a message there?
se
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
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.
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.
slowhands said: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
Hi, Steven,
I like this very much.
I like this very much.
I also think analog is kind of "Art" while digitals are "Exact science"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
lumanauw said: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
djk said:"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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