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Why is it PNP instead of PPN for transistors

hevans1944

Hop - AC8NS
Jun 21, 2012
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That DIY bread board sounds really cool! =)
We thought so, too, at the time.

Of course the ubiquitous "punch contact" bread-boards, used especially to prototype construction with dual-in-line packaged (DIP) parts, became available some ten or fifteen years later (I forget when they first appeared). IIRC, the lab where I was working at the time bought a version with a built-in five volt DC power supply for use with TTL integrated logic circuits. It had something like four rows of the bread-board blocks secured to a metal panel, and used Teflon-insulated pin sockets to connect the DC power supply to the "power rails" on the bread-board blocks.

Later we purchased several variations on this theme, including one that had a signal generator, several switches (push-button and toggle), and IIRC the (then) new red LEDs. It was quite exciting to be working in that lab in the late 1960s, and through most of the 1970s, until I finally graduated with a Bachelor of Electrical Engineering (BEE) degree in 1978 and a year later found a better-paying job.

There are several semiconductor devices that have only three terminals, but whose internal workings are not easily understood without the underlying theory. For example, the Silicon Controlled Rectifier or SCR is made from a stack of PNPN material. The anode is the P material on one end, the cathode is the N material on the other end, and the gate is the P material sandwiched in between the two N materials.

An SCR, through internal positive feedback, acts like a diode rectifier that is turned off until it is turned on by a positive trigger signal applied between the the gate and cathode terminals. Once it is turned on, it will continue to conduct as long as the anode is positive with respect to the cathode and a minimum "holding" current flows between the anode and cathode. The only way to stop an SCR from conducting after it is triggered is to either reduce the current through it to a value less than the holding current, or reverse the polarity applied between the anode and cathode.

Um, you could permanently stop an SCR from conducting by exceeding its maximum current rating, thereby melting the internal junctions and their wire-bonded connections to the outside world. What usually happens, however, is the SCR becomes a short-circuit when the junctions melt, possibly blowing fuses, tripping circuit breakers and/or causing fires.

Anyhoo, SCRs are fun to play with, but most power control circuits previously based on SCRs now use triacs, which is another three-terminal device that sort of acts like two SCRs wired in inverse-parallel, but with only a single gate terminal, not two like you would have if you actually tried to simulate a triac using two SCRs.

There are other examples of three-terminal semiconductor devices that do not yield much information when voltages and polarities are applied in all possible combinations. The now virtually obsolete unijunction transistor comes to mind.
 

ratstar

Aug 20, 2018
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Did you ever design a computer? Im feeling pretty confident that its going to be pretty easy in the end and I wont know what I was worried about.

Did u ever design an ALU? you can put one adder in, but if you put the amount of adders, one per bus bit, you can make a multiplier that runs in one hit. That means theres no penalty for a multiply over an add, like on a modern gpu.
And thats what you can do, if your making your own computer, you can make it how you damn well like.

Heres some history from a 40 yo. (bit younger than u I guess.)
That in the 70's before I was born, the microcontroller first appeared, but the guys already using physical operations in physical gates laughed at it, because those little microcontrollers dont actually get much work done compared to getting a full frame a clock cycle.

Thats just a guess why they were laughing.
 

bertus

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Hello,

I never designed a computer.
I did design a patern generator for repairing TV's about 45 years ago.
It contained about 30 TTL chips.

Bertus
 

Nanren888

Nov 8, 2015
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I suspect there's a cost to those one-cycle operations; namely realestate, whether it be silicon or chip count, or ROM space.
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I think you get close by pipelining & having pre-fetch. If you pipeline appropiotely, you get an answer per cycle, but not witout some latency.
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Maybe have a look at the equivalent gate count of some of those processors or multipliers you like.
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Maybe someone still makes bit-slice things?
Said it before: maybe FPGA is something to look at.
 

WHONOES

May 20, 2017
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Hello,

I never designed a computer.
I did design a patern generator for repairing TV's about 45 years ago.
It contained about 30 TTL chips.

Bertus
I designed a patient support monitor to detect if it had started going in the wrong direction and if so, to stop the motion. The limit was 3mm travel.
That was all designed using CMOS logic I think there was about 25+ IC's on a eurocard. That was in the late 1980's. I am / was an analogue designer rather than a digital designer so it was an interesting challenge.
 

ratstar

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I designed a patient support monitor

Do you still have the schematic? That would be cool.
And did it have an oscillator - or was purely just I -> O? Cause if its I to O, you dont need an oscillator because you only need to change the output when the input changes, so logic actually doesnt need an oscillator every single time.
 

Nanren888

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Asynchronous logic and switched/clocked/synchronous logic can both have advantages, depending on what you are doing.
Clocks are really good for knowing when to sample.
 

ratstar

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Did u mean you have to wait for the logic to "settle" so you dont get spurious outputs? Yep, but I wonder because "ripple" settles pretty quickly you can actually disregard the random values if you just want a direct link from in to out - the simplest form of machine, that would be. And a perceptron (artificial feedforward neural network) fits this case, but who wants to link all the synapses physically. :p
 

WHONOES

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Do you still have the schematic? That would be cool.
And did it have an oscillator - or was purely just I -> O? Cause if its I to O, you dont need an oscillator because you only need to change the output when the input changes, so logic actually doesnt need an oscillator every single time.
No I don't have the schematic. It is the property of the company I worked for at the time.
 

Nanren888

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Did u mean you have to wait for the logic to "settle" so you dont get spurious outputs? Yep, but I wonder because "ripple" settles pretty quickly you can actually disregard the random values if you just want a direct link from in to out - the simplest form of machine, that would be. And a perceptron (artificial feedforward neural network) fits this case, but who wants to link all the synapses physically
Add propagation delay and race conditions to "settling".
Transient behaviour of circuits, analog and digital, race conditions, analog perceptrons - all away from PNP transistor structure.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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He also did a lot of work on colours and how any colour could be made from just the 3 primaries.
Some, not all, visible colours can be made from just three primaries. WARNING! Wall of words ahead!

It's complicated, but it you understand the 1931 CIE chromaticity diagram (shown below) it becomes much clearer why any finite number of so-called primary colors.will always fail to produce a color gamut that includes all colors.

300px-CIE1931xy_blank.svg.png


The chromaticity diagram represents all visible colors, with purely spectrum (saturated, monochromatic) colors plotted along its curved outer edge, ranging from deep red with 700nm wavelength to deep violet at 380nm. The straight line connecting 380nm point with 700nm point is often referred to as the purple boundary. All "colors" outside the boundary of this figure are invisible and imaginary to the human eye. There is a third z-axis, not shown here, that completely defines all visible colors in terms of hue and saturation and intensity, but that is not important here. Also, because of color monitor limitations (or printer limitations for hard copy) it is impossible to view an absolutely accurate CIE chromaticity diagram.

The data points that constitute the colored area were empirically derived and averaged from color-matching trials conducted with thousands of volunteer participants. The normal color vision of most of the adult population is represented here. There will be exceptions, people who can see colors outside the boundary at wavelengths shorter than 380nm or longer than 700nm, but this is a very small subset of human population and it is not significant to this discussion. Also excluded are so-called "color blind" people. For everybody else, every possible visible color will occur within the boundary of the graph.

Tristimulus colors are visible colors that can be created by combining three "primary colors" selected from any colors within the boundary of the graph. This creates a triangle within the CIE graph, with the "primary colors" being at the triangle apexes, and all possible colors that can be produced by mixing various intensities of the "primary colors" occupying the interior area of the triangle. It should be clear by inspection that choosing spectral colors of 380nm (violet), 520nm (green), and 700nm (red) yields a triangle that encloses most, but not all, of the visible colors.

Obtaining saturated spectral light sources was not easy until laser diodes emitting visible wavelengths were invented. A ready supply of blue, green, and red monochromatic light is now available for constructing highly accurate video displays, but most color monitors get by with less than perfection, using three "primary" colors located well within the CIE graph boundary.

I agree with @WHONOES that the cerebral Scotsman James Clerk Maxwell is virtually unknown to most people, except for those of us who actually use his four equations describing electromagnetic wave propagation. Maxwell's equations completely describe electrical and electronic physics, although we usually use "formulas" derived from those equations for everyday work... Ohm's Law for example. There are many men (and women) of science whose names are virtually unknown, not because they didn't do good work but because they simply did not speak loud enough. Some, such as the Serbian-American Nikola Tesla, spoke perhaps too loud and too long, their legacy buried and ignored until re-discovered late in the twentieth century.

WHY IT IS "PNP" AND "NPN" INSTEAD OF SOMETHING ELSE

Getting back to the point of this thread, @ratstar is far from being a youngster (see post #23), or even a beginner at electronics experimentation. But his knowledge of semiconductor physics is currently meager at best. There is no denying that semiconductor electronics is complicated and by no means intuitive, or even remotely related to every day experience. Common sense does not apply. The math can sometimes be intimidating. It is worthwhile to try to understand what is going on.

Once anything technical is accomplished, the theoreticians always jump in to try to explain what is occurring. Sometimes they do get it right and suddenly everything becomes clear. Sometimes analogies are useful for visualization, but be very careful in trying to extend an explanation by analogy to encompass situations the analogy does not address. The hydraulic or water flowing under pressure analogy may help to understand electric circuits initially, but water in a pipe is not the same as electrons in a wire. Sometimes existing theory just doesn't provide a useful explanation, but that does not apply to semiconductors, which are understood extremely well as demonstrated by the production of billions, if not trillions, of semiconductor devices each year. The folks that make and sell semiconductor devices know WTF they are doing.

Any theory may still be incomplete, no matter how accurately it describes reality. Theories are an essential part of the "scientific method" of discovery and explanation. Usually the discovery occurs first and the explanation follows, but this isn't necessary. Black holes were "discovered" as a consequence of Einstein's Theory of General Relativity, but an actual black hole was not "found" until much later in the twentieth century, decades after Einstein. In the center of our own Milky Way Galaxy of all places. Some astronomers now believe that a black hole exists at the center of every galaxy, but there is no way to demonstrate whether that is true.

Just so you know, @ratstar, just about everyone "in the know" believes bi-polar semiconductor transistors operate the way they do because of two things: electrical field distributions within the semiconductor and the motion of charged entities (holes and electrons) in solids. Holes are somewhat difficult to visualize, since they represent something that isn't there, namely electrons, but holes exist and move around in a crystal lattice very much like electrons.

In a semiconductor material, such as silicon, holes are created by "doping" the crystal lattice, replacing just a few of the silicon atoms with atoms that will readily accept an electron. Materials doped in this manner are called "P-type" semiconductors. Doping can also be used to substitute in the crystal lattice a few atoms that will readily give up a free electron. Materials doped in that manner are called "N-type" semiconductors. The nomenclature of "P-type" or "N-type" has nothing at all to do with any applied voltage. The designation of PNP or NPN simply refers to the order in which layers of differently doped material are assembled to form a transistor.
 

ratstar

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I always get everything backwards, and some of the lectures on you tube are made PURPOSELY to confuse people!!!
So you can only really trust yourself, unless youve got a good feeling about a guy, it could be bullshit, and even then you could be tricked!! =)

Ive just learnt alot about the "invisible small rated components" that appear as a wire, or a part of a capacitor, resistor or inductor, even a transistor. So now because I didnt learn much about inductors, ive now studied them alot, cause even to include a wire, is to also include an inductor, so you better study them!!

Inductors are interesting how they produce pops/sparks!! But ive never actually put one in a circuit before, so im going to put together an lc oscillator, 3kilohertz means i can do it with a 400uf cap and a 400uh inductor, not too bad on the pocket, but have to wait till monday to check it out.

I hope I dont blow my speaker with the inductor...
 

Audioguru

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Why talk about making an audio LC oscillator with a extremely high value capacitor and a fairly low value inductor?
No schematic for us to see if it can produce enough output power to drive a speaker.

Also your speaker has no impedance and no power rating.
 

Nanren888

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I hope I dont blow my speaker with the inductor...
In a normal, modern, oscillator the drive limits the voltage.
Those sparks you get from big inductors are usually from suddent interruptions of the current, such as when it has substantial current running through it and you suddenly break the circuit. The stored energy in the inductor works to maintain the current, hwence a high voltage.
The voltage on an inductor is v = L di/dt, so that breaking of current, makes for a high rate of change of current, di/dt, and v goes up, sometimes arcing in air.
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For most modern oscillators, driven from low voltages, usually sinusoidal, the rate of change of current is limited, smooth, sinusoidal, so the voltage is limited, smooth, sinusoidal.. So the safety of your speaker and the rest of your circuit relates to choosing circuit configuration and voltages, impedances, gain in the speaker drive and such, but many an experimenter has done these things without bad consequence.
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HIgh voltage and current oscillations using spark gaps, another thing again. Not so often mixed with speakers nor the desire for audio frequencies.
Must be millions of audio oscillator circuits online, though most of the audio ones will likely be RC, or gate propagation delay based. THE LC ones, will often be RF, because of the normal range of L and C components found, used.
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I remember learning and getting some intuituive feel for what's normal by going through the circuits offered in experimenter kits. While I found them fascinating, they also gave me an idea of the configurations of standard circuit; a good starting point. Maybe not your way to take the path most travveled, but still, a source of information to consider.
Enjoy.
 

ratstar

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Why talk about making an audio LC oscillator with a extremely high value capacitor and a fairly low value inductor?
No schematic for us to see if it can produce enough output power to drive a speaker.

Also your speaker has no impedance and no power rating.

I know my capacitors fairly well, but I don't know much about inductors yet. I didn't know 400uh was a smallish inductor!!!

I'm thinking of using a piezoelectric, because they can take more power than a little magnetic speaker? I just want to make sure it doesnt blow up.

I don't know what impedance is either, only resistance.
 

ratstar

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Maybe not your way to take the path most travveled, but still, a source of information to consider.
Enjoy.

Your reading my mind, but I'm not a complete fool, I do see the clevorness of others, I'm getting better every day, but we have to keep things exciting. :)

The strange pathway I want to go to be original, I do have a funny feeling its not original anyway, so I dont have to change - theres not much absolutely grander about it, I dont mind.

If your machine works, it agrees with everyone elses machines, the truth is where we come to be the same and like each other, even if it seems wierd, if it works - the truth agrees with itself, and it is the same in that way, and we can get along hopefully.
 
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Audioguru

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A piezo speaker is very small so it produces only high frequencies. It has strong resonances at some frequencies and low output between resonant frequencies. It is made for a beeper.

Impedance is the resistance at an AC frequency. Because a coil and magnet speaker is an inductor its impedance is higher at higher frequencies.

The frequency response of a good speaker is a straight horizontal line from a low frequency (30Hz to a high frequency (18kHz).
Here is the horrible frequency response of a piezo speaker that is all over the place with a few loud frequencies (2.5kHz, 5.5kHz and 15khz) and a few faint frequencies (below 2kHz, from 3kHz to 5kHz, and most higher frequencies.
 

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ratstar

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A piezo speaker is very small so it produces only high frequencies. It has strong resonances at some frequencies and low output between resonant frequencies. It is made for a beeper.

But they take alot more current before they pop right? I'm just worried ill go through 10 magnet speakers before I finally get the LC oscillator to work. Waste of good technology.

LC oscillators are high frequency, so it suits a piezo in a way.

Thanks for telling me about the impedance, and that piezos have resonating problems. cheers.

Piezos are easier to make yourself - as a flat thing, I think, but I think I'd rather buy one just to make sure it works.

And- you can get piezos that operate at 3k right?

<edit]> sorry i meant electrostatic not piezoelectric but i just looked on the internet and they cost too much... and they take hi voltage..</edit>
 
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Nanren888

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I know my capacitors fairly well, but I don't know much about inductors yet.

I gioogled and found

https://web.stanford.edu/class/archive/engr/engr40m.1178/slides/reactives.pdf
which includes

upload_2021-2-14_12-38-14.png


The calculus may not be for everyone, but, notice that if you swap current (i) for voltage (v), these look the same.
That is, any intuition, understanding, you have of capacitors, will help you with inductors, if you swap voltage and current.
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The equations above also tell a story as they are. Integrate the capacitor one and it says for a capacitor, the voltage is proportional to the integral, sum of all the current that went into it. Or as written, the current is proportional the the rate that the voltage changes.
The inductor one says what I said before, the voltage across an inductor is proportional to the rate of change of current, hence things get interesting when you break the circuit current suddenly.

Hope it help.
Enjoy
 
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