Electronics for the right-brained

How about you get yourself a subscription to an electronics magazine? Something like Silicon Chip perhaps. Some of these can be subscribed to on-line, so there's no massive cost of postage.

There used to be a heap of titles (Talking Electronics was one) that covered basics. Their web site is still updated and has lots of useful stuff.

 

Yeah, there is a limit as to how much electronics you can do with no mathematics at all. (And that limit is that you are limited to building circuits designed by others, with the component values they have chosen, and with only notional understanding of the circuit operation)

I'm not saying that that means you can't do anything. It's a point where many hobbiests get to.

The next step is the basic arithmetic of ohms law, which (frankly) you really aren't safe to be let work unsupervised unless you know and understand this.

When you say "no numbers or mathematics, I hope you don't mean this.

Simple algebra and arithmetic can carry you a long way, as it is all that is needed to understand things like gain of transistors, much work with op-amps, and pretty much all the DC circuit operation you can handle.

However for *real* understanding, you need to be able to work (at least once) with various "higher" mathematical processes. These eventually (most often) turn out to produce more simple arithmetic, but to understand how to apply them it is best having worked through the heavy math at least once.

Ohms law, for example, is a simplification of some really tricky math. It is simplified after making certain assumptions that apply most often in the real world to most things.

As has been suggested before, H&H is actually *very* light on with the math. Sure, it contains some of the formulae, but the text doesn't require that you understand them (other than for the first chapter -- but you can ignore that if you're comfortable with things like ohms law and resistors in series and parallel).

I'll accept that H&H is not the book for you, but without some math, you're going to limit your designs abilities to batteries, switches and incandescent globes.

 

by which you mean silicon bipolar junction transistors, not jfets, mosfets, or any of the other less common transistor types.

can be used as

more accurately, they use one current to control another

well, actually it flows in exactly the opposite direction since the arrow points in the direction of conventional current which is backwards. But yeah, since we can think about conventional current, the arrow points that way.

yes, usually, but some have only 2 (typically optical devices)

no

no

yes (normally)

no

normally

that's what you just said, but what about leakage from the collector to the base?

with the assumption in my first line above

more restatements of stuff above

more restatement, but "splits", and "combines" are not correct understanding

no. It must be positive wrt the emitter. Both may be -ve, just the base may be less so.

see above, but backwards

yes

no. approximately 0.6V, but it depends on some other factors. Also note that this is specific to silicon transistors (not that you see too many others)

see above

no (it's not quite that simple)

no

Remember that you spoke about transistors being current devices above, and now you're talking voltages.

It's not quite that simple, but this is the definition in one configuration

of course, there's hfe and hFE. They refer to forward current gain in a particular configuration. But yes, that equation holds

no

no. There are many types of transistors, you've simply picked out BJTs (and silicon ones) for this list.

not sure what you mean here

often, but not always

only if you define it as such. I can show you some very small transistors capable of very high currents. What differentiates them is the power they can dissipate (hence why one might call them low or high power). Even there, this is a continuum.

OK

OK

no, this is medium power, look at something like the venerable 2N3055 -- especially in TO-3.

What about the MJ2955? As I said, there is a continuum of values here. Another important one is the various Vce specifications. Can the transistor be used in a 30V circuit, 50V, 80V, 200V, or 1000V circuit?

Your list represents a set of assumptions and generalizations you (or someone else) has made. Pretty much all of them are wrong in some form (and it would take pages to get some of them close to right).

To gain further understanding you need (many things, but one is) to see an explanation of the physics of a transistor. You don't need to understand it completely or be able to regurgitate it, but the list above tells me you really haven't seen it.

Possibly a quick look at the other types of transistors so you don't think BJT's are the be all and end all of them.

I just flipped through the first 10 or so pages of the introduction to transistors in Horrowitz and Hill. The most advanced mathematics was:

1) simple arithmetic (division and multiplication)
2) the use of the delta symbol meaning "change in"
3) the use of the symbol || meaning "in parallel with (so R1 || R2 means 1/(1/R1 + 1/R2) -- just a bit of shorthand)

I could point you to other books that have pages of calculus describing the same things.

 

Skip Thevinen and all of chapter 1. Skip ahead to the chapter on transistors.

 

Well, there's high and there's HIGH!!!

Sure 450 for a BJT seems high (and I'm sure I've seen a device with a max hfe of 800). If you look at darlington configurations (don't bother with this now) then gains in the tens of thousands are distinctly possible.

However, a BJT requires a base current (no matter how small) to control a larger collector current.

If you look at FETs, you will notice that rather than being current controlled, they are voltage controlled. To simplify things somewhat, this means that no current flows into or out of the gate terminal. As such, the current gain is effectively infinite.

In real life, there are leakage currents and other factors, but still, the current gains are astonishingly, mind-bogglingly high. They're so high that you'll almost never see figures quoted, they become so high as to be meaningless.

No. It's all about the control terminal.

Let's think about the base of a bipolar transistor. It is forward biased in normal operation, and the Vbe barely changes as the current through it increases. It may change from 0.62 to 0.6205 V (say) as the current changes from 1 to 2 uA. and assuming a gain of 100, the collector current may change from 100 to 200uA (0.1 to 0.2 mA. If the power supply is 12V, and the load resistor is 47k, the voltage at the collector changes from 7.3V to 2.6V. That's a change of 4.7V for an input voltage swing of 0.0005V, a gain of 9400.

In contrast, With a mosfet, the gate terminal may need to swing several volts to change the device from being off to on, but the current it might allow to pass through it could be tens of amps. In this case, even if the drain voltage swing all the way from 12V to (say) 0.5V with an input swing of 2 volts, the voltage gain is about 6, bit assuming an input current of (say) 10 nA, and an output current of 1A, the current gain is around 100,000,000.

OK, skim over the details, but in these examples, you can see that a BJT has a current gain of 100 compared with 100,000,000 for a mosfet, and the voltage gain is 9600 vs 6.

That's one reason. Another is that they are happier switching moderately large currents. It often boils down to current gain. This goes hand in hand with being able to switch very close to supply rails, and that can be important too.

 

No, where ever Steve has said No, it really is No you maybe were running at ~ 50%

Its all good tho mate you are asking questions doing some reading and learning and thats what it is all about !
Keep reading H&H and when you find things you dont understand just ask questions on those points ad you have started to

cheers
Dave