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Topic: Solar Cell Preamplifier Design Problem

Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 12-09-2005 08:34 AM

quote: Phil Hill
Mark, get off your high-horse. It's an insult to MANY FT members that YOU think there are BETTER "qualified" people (electrical engineers, techs, etc) elsewhere just points to insulting the talent here.

Phil,

Sorry bud but that is the truth. Smart F-T members already know that. If its audio design Marin wants to learn this is DEFINATELY NOT the place to learn it!

There is only one degreed electrical engineer around here that I am aware of that really knows his stuff... and is sometimes willing to share his knowledge with us. There are more than I can count over there and many with decades of experience in every facet of audio design. Several of the audio industries top engineers hang out over there... people like Erno Borbley, John Curl, Nelson Pass, Jan Didden, and a bunch of others, yes these guys also design your beloved "commercial" stuff as well. If you wouldn't want your questions answered and your designs tweeked by these guys fine, I guess you know more than they do.... but for the rest of us that know who these guys are it's a priveledge to have contact with them.

Mark

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 12-09-2005 02:46 PM

I'm one of many degreed electrical engineers who participate on Film-Tech, but it's been years since I've had to design any electronic circuit for a living. The experts in designing audio amplifiers are the ones who do it for a living, and have their designs proven by success and reputation in the market. A BSEE is only the beginning. Experience is the real education.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 12-09-2005 05:16 PM

quote: John Pytlak
Experience is the real education.

Well put John! And thats rally the only way Marin is going to learn... copying someone elses design doesn't really ause much brain growth. Its interesting that you atarted out with a BSEE.... How on earth did did you go from electrical engineering to making film at Kodak?

Mark

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000

posted 12-12-2005 06:47 PM

Marin, please re-send me your email directly to my private email and include your addr so I can send you the cell as you requested.

(Sorry, I don't know how to reply thru FT and insure you get my response.)

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 12-14-2005 10:49 AM

quote: Mark Gulbrandsen
Its interesting that you atarted out with a BSEE.... How on earth did did you go from electrical engineering to making film at Kodak?

The transition is easy, and many Kodak film engineers have backgrounds in electronics. Lots of image science has its roots in electronics and communication theory. The work of Nyquist, Maxwell, Fourier, Schade, and their successors are well known and often used in image science. And since the majority of Kodak's revenue now comes from digital imaging, EE's and IT's are in ever increasing demand at Kodak.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 12-15-2005 11:24 AM

That interesting John, I never would have thought the works of those guys would have anything at all to do with film... but then I never studied how film is made to any great extent, just how to use it.

Thanks!
Mark

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 12-15-2005 11:42 AM

A film latent image is formed by electron transfer:

http://wwwcaen.kodak.com/US/en/motion/products/v2/2electron.shtml

quote:
In Kodak’s two-electron sensitization scheme, an appropriately designed electron donor molecule, X–Y is added to the photographic dispersion. This molecule transfers an electron to the oxidized dye to give a radical cation, X–Y•+. The radical cation then undergoes a fragmentation reaction to give a radical X•, and a stable cation, Y+.

The radical X• can inject an electron into the silver halide conduction band. In this way, the oxidized dye, which is a strong oxidant, is replaced by the radical, X•, which is a strong reductant. Thus, the two-electron transfer scheme has the potential of doubling the photographic speed because two electrons are injected per absorbed photon.

Film has many similarities to solid state electronics. But it makes better images. [Wink]

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-18-2005 08:44 AM

Thanky you for all answer, it's help me a lot!

Ok, you probably all know reason why i work with photodiodes (untill i get phil's cell :-) ).

This is schematic of preamp with photodiode and photodiode is biased with DC voltage.

What you think what level of biasing voltage, measuren on input rail could be wright for minimum distorzion, and does distpruion concidering of a bias voltage???

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-19-2005 03:33 PM

No comments?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 12-19-2005 05:10 PM

So Mark...I know I'm one of the degreed Electrical Engineers over here...however, as John has said, experience is where it is at when it comes to good designs. Sure, one must have some sort of raw talent and proper education to use that talent but one must play with it a bit to get really good.

Perhaps you are thinking of Ray Derrick? I suspect he is a double-E and certainly knows his stuff. I'm pretty sure Oscar is not a double-E yet also seems to know his stuff.

Who is the EE you are thinking about?

As to designs...there is nothing wrong with looking at what has been done to get one started. It is pointless to regurgitate an existing design (and also violates copyrights). Presumably the reason for a new design is a desired design does not exist or exist in a form you need it.

As to the design as it stands...I would get away from the single-ended stuff...you WILL have noise in the system from ticks and pops. I would also limit the frequency response going into your op amp with a single pole low-pass filter. Your HPF probably doesn't need the second cap in that with a 12V power supply you probably will never have the cap reverse polarized. Also look into the lowest frequency you will possibly need (there is going to be mostly noise and crap down there) and use the blocking capacitor as your first HPF.

Your adjustable gain section could also use some work. What is the range you really need? Again, what is the frequency range you really need?

Do you have any simulation software? You might find it interesting to first simulate your circuit before building it to get all of the particulars set. Sweep the frequency and make sure you have something that is stable before you hook speakers that might suffer first.

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Marin Zorica
Jedi Master Film Handler

Posts: 671
From: Biograd na Moru, Croatia
Registered: May 2003

posted 12-19-2005 05:59 PM

Thanks Steve!

Yes i know for response limiting, but mostly on this circuit i want to know about photo diode DC bias!

A know all ready about cell and stuff, but this is situation i have so please HELP!

Is it possible to obtain good sound with photo diode??, off course properly biased. Mostly i thinking about low distortion, because freq. response isn't problem. I can upgrade this adding regulative resistor so i can change DC bias voltage, i put 100K resistor on DC bias to save photo diode for over current, it that ok?

What's HPF???

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 12-19-2005 07:44 PM

Sorry...HPF = High Pass Filter.

As to the photo-diode...I have no personal experience in properly setting one up (except maybe in a physics class many moons ago) thus I would hesitate to advise you on that part of the circuit.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 12-19-2005 10:44 PM

quote: Steve Guttag
Who is the EE you are thinking about?

Indeed Ray is the first one that comes to mind that has posted on these forums, but is rarely here any longer, most likely just too busy as most highly qualified people of his type are. Oscar would also be a good choice and he has also had sucessful products over the years. Other than these two I can't think of any analog designers that have frequented this forum that have had truely sucessful products. Ray in my mind is without doubt the most sucessful analog-cinema designer that I know of. Oscar also comes to mind but is Oscar still with us? I heard from another member that he is now with Leviton. All the other people that I mentioned back in the other post are also all highly sucessful engineers that have all developed multiple highly sucessful product lines in varying audio fields over the years. Some of them also have other pertaining dergrees. Between those people there are easily over 300 collective years of audio design, perhaps more.... and they are all accessable through DIY. I am sure that both Ray and Oscar either know some of those people or certainly know of them. A few of them have also made contributions to cinema audio over the years. Marin is aware of that and is also a member over there. Its the best place I know of on the net to learn about designing circuits of just about any type.... The hits that site gets daily is staggering and you are very likely able to get assistance from some of the top engineers in audio on a project over there.

As for looking at others designs.... thats pretty much a given. Anyone with any ounce of interest in how things work are going to do that. Some of us look at the design and schematics in order to enable us to better utilize a product. You can certainly learn about different topologies and types of designs by looking at schematics. However, looking at topologies and others designs doesn't teach you HOW to design. What I read in between the lines in Marins original post and what Marin later confirmed was a desire to learn how to design a circuit. Reading books, going to school, and above all experimentation and achieveing the results you projected are whats going to teach you how. Its completely up to an individual to carry that out to what ever level he/she is interested in taking it to.

On the balanced issue I couldn't agree more. Noise will always be an issue with a single ended circuit, especially in a noisy environment like the typical booth. Its either going to require a transformer input, or a true balanced circuit to get to the right place. This could be implemented with IC's or discrete circuitry but the latter would take quite a bit of work. In fact there is an interesting paper over at Jensen Transfomrers that is good reading on this subject. Another very unique circuit designed and patented that would make a great cell preamp is the Super Symetric fully balanced/cross coupled circuit. This patented circuit and many other patented circuits are available for non profit use by permission of their designers for members over at DIY. I have built line level circuits based on this patent that are pretty amazing. BTW: this circuit is fully capable of either low level work or power amplifier work. Because this circuit has so many exceptional qualities there has also been much interest in turning this circuit into IC form and this may be happenning sometime in the near future.

I have to chuckle.... Even though one member here claims that the solor call preamp "has been researched to death" it would appear to me that it really hasn't been.

Mark

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