Andrew T's definition is right but simplistic and applies *only* to pure AC, fine to explain transformers and such, but insufficient to explain (single) transistor or tube amplification stages .... which is what we are discussing in this thread.
Probably the OP would understand it much better if somebody told him that tubes and transistors pass a *compound* current, which has *two components* , a DC one and an AC one.
And there´s no *magic* involved.
Audio signals are AC.
Capacitors pass AC and stop DC, so passing audio signals through them is not magic but the natural way they work.
In principle, yes, (single) tubes and transistors work with DC.
When receiving an AC audio signal at their base/grid (where there is *also* some DC, called BIAS) DC current through them gets MODULATED which means "gets changed following the input signal" so it now has TWO components, one DC and one AC.
The new AC component is usually (there´s one exception) much higher than the original AC one, so we call that AMPLIFICATION.
Since we want it but not the associated DC , we use another capacitor at the output to pass AC signal but kill the DC component.
So now we understand two apparently conflicting statements:
* Audio is AC
* Transistors/tubes work with DC .
I suggest to the OP to study step by step, getting the concept buried in any definition, beyondnrepeating it bu heart, there's no other way.
When asked, I suggest everybody to learn *first* ***PHYSICS*** , Electronics is just a chapter of it.
Get a 40 to 80 years old (no kidding) Physics book, the one meant to teach 16/18 year olds (don´t mention a specific school class or year because it varies on every country) , specificallyn the one teaching Electricity and Magnetism.
It will teach you what 's:
Electron - current - conductor - insulator - battery - volt - ampere - resistance - power - capacitor - meter - coil - inductance - transformer - magnet - magnetism - electromagnet - motor - generator - etc.
Once you *understand* that, and can calculate current through a resistor based on voltage applied to it, power dissipated, etc. , Electronics is a piece of cake.
Now you are trying to cram a zillion seemingly contradictory things all at once inside your head, and it will burst
Probably the OP would understand it much better if somebody told him that tubes and transistors pass a *compound* current, which has *two components* , a DC one and an AC one.
And there´s no *magic* involved.
Audio signals are AC.
Capacitors pass AC and stop DC, so passing audio signals through them is not magic but the natural way they work.
In principle, yes, (single) tubes and transistors work with DC.
When receiving an AC audio signal at their base/grid (where there is *also* some DC, called BIAS) DC current through them gets MODULATED which means "gets changed following the input signal" so it now has TWO components, one DC and one AC.
The new AC component is usually (there´s one exception) much higher than the original AC one, so we call that AMPLIFICATION.
Since we want it but not the associated DC , we use another capacitor at the output to pass AC signal but kill the DC component.
So now we understand two apparently conflicting statements:
* Audio is AC
* Transistors/tubes work with DC .
I suggest to the OP to study step by step, getting the concept buried in any definition, beyondnrepeating it bu heart, there's no other way.
When asked, I suggest everybody to learn *first* ***PHYSICS*** , Electronics is just a chapter of it.
Get a 40 to 80 years old (no kidding) Physics book, the one meant to teach 16/18 year olds (don´t mention a specific school class or year because it varies on every country) , specificallyn the one teaching Electricity and Magnetism.
It will teach you what 's:
Electron - current - conductor - insulator - battery - volt - ampere - resistance - power - capacitor - meter - coil - inductance - transformer - magnet - magnetism - electromagnet - motor - generator - etc.
Once you *understand* that, and can calculate current through a resistor based on voltage applied to it, power dissipated, etc. , Electronics is a piece of cake.
Now you are trying to cram a zillion seemingly contradictory things all at once inside your head, and it will burst
Very poor analogy. Maybe compare to a CVT. Still cars are not a good model.
Gain can be positive or negative.
First gear is more what you're stuck in when you're struggling to comprehend a design. Second gear is what happens when something finally starts to make sense. Third gear's when you get something built. Fourth, when it works but is just a PCB on the floor. Fifth is when you're sitting back and looking at the pretty case you've just stuffed it in and everything still works.
Reverse is what happens when you let the blue smoke out.
Reverse is what happens when you let the blue smoke out.
Dividing current/voltage strictly into AC and DC in electronics is a bit like dividing organisms into species in biology: a useful place to start but gets you in a mess if you try to push it too hard.
It leads to arguments about whether DC is constant (or nearly so) or unidirectional (but possibly changing quite a lot). Eventually some people realise that Fourier solves the dilemma; others don't get that far.
It leads to arguments about whether DC is constant (or nearly so) or unidirectional (but possibly changing quite a lot). Eventually some people realise that Fourier solves the dilemma; others don't get that far.
You don't really start learning,
Until something you make doesn't work..Then its down hill all the way..
If your lucky the fog clears or someone who can "John and Jane" it and explain how to understand steps in..
Many give up at this point....But help is at hand "The Ladybird book of electricity" Year 5...LMAO
(It has big writing as well) and lots of pictures..
Regards
M. Gregg
Until something you make doesn't work..Then its down hill all the way..
If your lucky the fog clears or someone who can "John and Jane" it and explain how to understand steps in..
Many give up at this point....But help is at hand "The Ladybird book of electricity" Year 5...LMAO
(It has big writing as well) and lots of pictures..
Regards
M. Gregg
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Gadzooks! I can only imagine the poor original poster having gone back to university and changed courses to become some form of zen monk.
I guess a DIY site doesn't promise to help confused undergrads, well maybe the above "stuff" (i am guessing expletives are not cool) will convince the poor sod to (a) start studying and (b) start building!
What surprised me was a degeneration of discussion into a philosophical black hole, and nobody thought to mention that there is a DC operating point with perturbations from this. WTF.
I guess a DIY site doesn't promise to help confused undergrads, well maybe the above "stuff" (i am guessing expletives are not cool) will convince the poor sod to (a) start studying and (b) start building!
What surprised me was a degeneration of discussion into a philosophical black hole, and nobody thought to mention that there is a DC operating point with perturbations from this. WTF.
On a serious note,
No1 leave the Maths out of it and understand....
You need to throw away what you think you know.
Learn about something like how a transformer works<<don't get into high tech just the basic mechanics.
Then learn how a generator works..Again forget what you think you know.
Then learn how to make a very simple DC supply and how a diode bridge works.
Then what smoothing does to the supply after the diodes and what ripple is.
Forget anything else this will give you an appreciation of what AC and DC is...very basic however its a building block.
Learn to read basic drawings<<<not the hadron collider!
A simple on off circuit with a couple of transistors and logic.<<not a signal..on and off.
Then the difference between PNP and NPN (transistors)and the input to the base and why its different. (No maths)..simple appreciation of the difference and why its different.
Now look at BASIC Ohms law...and BASIC Kirchoff's law<<<don't get caught up in the maths..its the understanding of whats going on and why..
Now you might have a chance at looking at sine wave signals applied to a transistor and what is peak and RMS (AC) and the link to DC.
At this point don't go off at a tangent and immerse yourself in the maths of power factor correction etc. (Stay on course)
Start learning about components...
Regards
M. Gregg
No1 leave the Maths out of it and understand....
You need to throw away what you think you know.
Learn about something like how a transformer works<<don't get into high tech just the basic mechanics.
Then learn how a generator works..Again forget what you think you know.
Then learn how to make a very simple DC supply and how a diode bridge works.
Then what smoothing does to the supply after the diodes and what ripple is.
Forget anything else this will give you an appreciation of what AC and DC is...very basic however its a building block.
Learn to read basic drawings<<<not the hadron collider!
A simple on off circuit with a couple of transistors and logic.<<not a signal..on and off.
Then the difference between PNP and NPN (transistors)and the input to the base and why its different. (No maths)..simple appreciation of the difference and why its different.
Now look at BASIC Ohms law...and BASIC Kirchoff's law<<<don't get caught up in the maths..its the understanding of whats going on and why..
Now you might have a chance at looking at sine wave signals applied to a transistor and what is peak and RMS (AC) and the link to DC.
At this point don't go off at a tangent and immerse yourself in the maths of power factor correction etc. (Stay on course)
Start learning about components...
Regards
M. Gregg
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Suppose you have a 'perturberating' DC signal, superimposed by a negative DC signal, the net result is an AC signal.
DC + DC = AC ?
WTF ?
I have my master-degree micro-electronics, but before that i did 4 years electronics and i havo no idea how it's called by you, with master-degree i mean university and then one step below ...??? the signature before your name is ing. and with univirsity is ir.,de but
these days the educations are far less analogue oriented then when i studied, while infact offcourse the ic is analogue from the inside.
And every day is a learning day.....look at all the components on the market(discreet) only have been introdused this year.... I'm a lineair components fan, but you keep reading.. my point:learn the basics well, and don't go developing which(most copying),
it gives a better feeling and don't try to understand everything .It's impossible..
goodluck, richard(netherlands)
these days the educations are far less analogue oriented then when i studied, while infact offcourse the ic is analogue from the inside.
And every day is a learning day.....look at all the components on the market(discreet) only have been introdused this year.... I'm a lineair components fan, but you keep reading.. my point:learn the basics well, and don't go developing which(most copying),
it gives a better feeling and don't try to understand everything .It's impossible..
goodluck, richard(netherlands)
Over here, BS, MS, PHD. We call the last one "piled high and deeper" as PHD's seem to know everything about almost nothing which makes them useless as an engineer who needs to know a bit about everything.
Seriously, I work with a lot of PHD EE's. Tough degree. Some of the very smartest folks I know have their doctorate in EE. (or most never finished as they had a job and family preventing their thesis from being finished) The smartest man I know has the amazing understanding that everyone in the world knows something he does not, and he would always listen.
Seriously, I work with a lot of PHD EE's. Tough degree. Some of the very smartest folks I know have their doctorate in EE. (or most never finished as they had a job and family preventing their thesis from being finished) The smartest man I know has the amazing understanding that everyone in the world knows something he does not, and he would always listen.
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