Alternative means of producing amplification

[TheVictim]

I've experimented with making "transistors" and other devices to produce electrical gain in a variety of ways. I'd like to hear from others who like to do this and what your results were.

Here is what I've done so far:

1) Potatoes. Bell labs first transistor was actually made from a potato. My gain maxed out at about 3. I believe this works in the same manner as the Electrolytic Transistor which was actually built in 1910.

2) Corrosion on galvanized steel. The black spots can be catwhiskered to form something that will exibit gain, but is a bit touchy. I could get a gain of about 10 from this. Takes a LOT of trial and error to find the sweet spot. There are some web pages such as **broken link removed** that detail experiments with building oscillators.

I've contemplated using a lamp biased with DC to illuminate a Cds photoresistor, but I suspect the frequency response is going to suck. It might work for a power amplifier, but the Cds cell isn't going to be able to handle a large current flow.

Edit: I also want to experiment with AC voltage dividers. Would using a junction diode or a varactor to produce the needed variable capacitance be "cheating"? I think the gain could be made pretty high with this, and frequency response would be quite good.

Any other ideas? I have no practical use in mind, just playing around.

 

[j.p.bill]

1. Wha? Seems to contradict transistor theory. Was the potato PNP or NPN? Or is this some method that affects a conduction path between a pair of electrodes?

2. That is similar to the razor blade rectifier used by troops during WWII. The oxide in a Gilette Blue Blade exhibited an effect similar the the "usual" galena crystal in a crystal radio.

You're right about CdS cell response is correct. It does suck. There are better ways - think transistors.

Do you percieve some essential difference between a voltage divider that handles DC and one reducing AC? How can a voltage reducing arrangement be made to produce gain? If a divider drops the voltage, it must also limit current. Look into autotransformers.

 

[ericgibbs]

Never heard of a potato transistor, potato battery, yes, with zinc and iron electrodes.

Made a couple of transistors in the 1960's using a broken open germanium type OA47 diode and a razor blade edge, the edge pressing on the diode semi, then dis-charged 0.1uF cap thru the blade/semi, to give a good electrical bond. Bottle cork as mounting base.
Gain was about 3, but they are totally useless for a practical circuit.

Get some plain copper washers, blacken one face of each washer, using the black smoke from a candle, pack them together on a wooden pencil as a former and you have a rectifier, of sorts.

Made varactor diodes from reversed biased diodes, for Foster-Seeley FM detectors, back in the 1950/60's when FM radio started up.

Played with cats whisker radio's using broken OA47's.
Before OA47's , used galena crystal with a very long aerial, for radio back in the 1940's.

 

[TheVictim]

I had an old issue of QST magazine where they actually made a final RF amplifier with a potato. It got too hot and started to smell good to their cat, so it actually got eaten!

There is some info floating around about electrolytic transistors, just not very much. I'd like to learn more about them if someone has some data that Google isn't bringing up. I'm pretty sure the potato is acting similar to that. Two wires are placed fairly close together into the potato and a current is ran though until an area turns green. A 3rd wire is added next to the green spot. Using the green area as a gate, it functions like a FET.

The idea of a capacitive voltage divider amplifier would be two diodes each reversed biased with an adjustable source of DC so their reactance to the AC frequency supply would be identical. Your signal to amplify would be put across BOTH diodes to provide more gain. The difference in capacitance between the two will imbalance the voltage divider. A much higher AC voltage is put through them in series like a regular voltage divider. This should show a voltage gain at the center tap. Your amplified signal is going to be AC of course, but this can be an advantage. 2 sets can be used to amplify the whole wave. If your AC supply to the voltage dividers happens to be a frequency you want to transmit at, this should create amplitude modulation at the supply frequency.

 

[Roff]

The idea of a capacitive voltage divider amplifier would be two diodes each reversed biased with an adjustable source of DC so their reactance to the AC frequency supply would be identical. Your signal to amplify would be put across BOTH diodes to provide more gain. The difference in capacitance between the two will imbalance the voltage divider. A much higher AC voltage is put through them in series like a regular voltage divider. This should show a voltage gain at the center tap. Your amplified signal is going to be AC of course, but this can be an advantage. 2 sets can be used to amplify the whole wave. If your AC supply to the voltage dividers happens to be a frequency you want to transmit at, this should create amplitude modulation at the supply frequency.

Can you post a schematic of this? I'm having trouble visualizing it.

 

[CheapSlider]

Auxetophone

A true alternative would be non electronic.
Mechanical amplification was used before valve amplifiers were available. There was the clockwork **broken link removed**or for really loud sound the compressed air powered **broken link removed** - apparently the principle is still used in high level sound generators.

 

[TheVictim]

Power amplifiers would be MUCH easier to implement than preamps for audio.

I'll dust off the Amiga and draw up a schematic for the proposed voltage divider amplifier. Heck, if I'm going to do that I might as well build one too. If I can get it to work I'd like to find a method of electronically controlled variable capacitance that does NOT involve semiconductor diodes just for the heck of it.

Edit: I emailed the ARRL to see if they could dig up the QST article for me. The have already responded and are having someone check the archives. It was a hilarious story, I hope they can find it.

 

[TheVictim]

Actually J.P., if you think about it, a common emitter transistor amplifier IS a voltage divider. The input signal isn't the signal that is being divided, it is your Vce supply that is divided between the transistor and your collector resistor. A common collector amplifier functions like a current divider in the same manner, it all depends on where you take your output from.

If the capacitive or inductive reactance on one side of an AC voltage divider can be made to vary in proportion to a signal, the amount of a separate AC supply voltage it will drop on each side will also vary in proportion.

EDIT: The ARRL pointed me in the direction of this book

Instruments of Amplification
-- Fun With Homemade Tubes, Transistors, and More

written and illustrated by H. P. Friedrichs

Are you interested in building sensitive audio amplifiers from magnets, a shoe-polish tin and a couple of carbon rods? How about a working triode vacuum tube built from candle holders and old glass ashtrays? Perhaps you’d like to construct your own transistor from plumber’s fittings, glass beads, and a tiny crystal. If so, you’ve come to the right place.

Instruments of Amplification is jam-packed with history, science background, basic theory, and hard-to-find hands-on details pertaining to the construction of an amazing array of homebrew amplifying devices. Rooted in the same ‘build-it-from-scratch’ philosophy that made his first book, The Voice of the Crystal, a success, Instruments of Amplification reduces complex devices to their essential elements and then shows how they can be constructed from commonly available materials.

In the process of building, you’ll also learn secrets that will find application to the other projects. Learn to drill a hole in a glass, generate high voltages, or create and measure a high vacuum. Learn how to dismantle a light bulb, harvest carbon from old batteries, or deposit a layer of metal onto a glass so thin that it is transparent! How about creating your own primitive semiconductor materials from garden-shed chemicals? The list goes on and on!

The wealth of information contained in this book is augmented by 150 photos, illustrations, and engravings, in addition to numerous charts, tables, and formulas. Readers interested in further exploration will appreciate the 120+ references to period books, magazines, CD-ROMs and Web sites.

302 pages. © 2003, by H. Peter Friedrichs.

(ISBN: 0-9671905-1-7) #9163 -- $19.95

Sounds like a lot of fun. I'll try and hunt it down.