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Stoneman
I HAVE NO LEGS??!?
 
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Class AB audio power amplifier built from scratch [electronics]

from wikipedia:

AB push–pull circuits are the most common design type found in audio power amplifiers. Class AB is widely considered a good compromise for audio amplifiers, since much of the time the music is quiet enough that the signal stays in the "class A" region, where it is amplified with good fidelity, and by definition if passing out of this region, is large enough that the distortion products typical of class B are relatively small. The crossover distortion can be reduced further by using negative feedback. Class B and AB amplifiers are sometimes used for RF linear amplifiers as well. Class B amplifiers are also favored in battery-operated devices, such as transistor radios.


I put the box together from a small box of chocolates I found laying after my desk after I ate them yesterday on the 20th of april... /a[m] I spray painted it with black glossy paint I found laying around the house, and made the window out of a piece of plastic I found in the back yard while spray painting.


6 transistors in total, all bjt's. The two bigger ones are power transistors so that it won't get too hot, mostly npn's but two out of the 6 are pnp's to help limit the current.


testing it in the lab before I trimmed the board and boxed it up... off a 5 ohm load we get this great output wave form:



thats 6.3 volts peak to peak with a .3 v peak input signal... I was shooting for about 1 and a half watts for the load, pretty close.



the guts I'm not the best at soldering but I get the job done




annnnnnnd All done.
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[QUOTE=littleho;24346404]what the hell are stoneman and DM talking about then?? I FEEL LIKE IM TAKING CRAZY PILLS[/QUOTE]
Old 04-21-2009, 08:57 PM Stoneman is offline  
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sanjay
 
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good show!
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Old 04-22-2009, 08:15 AM sanjay is offline  
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Whitebread
 
A sweet ass thread about what you can do with electrical engineering and only 1 reply..........shame
Old 04-22-2009, 10:14 AM Whitebread is offline  
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DigitalChaos
 
any chance of posting the schematics and/or build plans?
cool stuff
Old 04-22-2009, 10:20 AM DigitalChaos is offline  
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Jose Theodore
[ Mr.Burn ]
 
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nice, i did one for sine, square and triangular waves it was cool ... although the sine wave was slightly buggy :P
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Old 04-22-2009, 10:23 AM Jose Theodore is offline  
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Jose Theodore
[ Mr.Burn ]
 
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i'll also be doing a class on the principles of communication systems this summer Fourier Transforms here i come
Old 04-22-2009, 11:25 AM Jose Theodore is offline  
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Skadebo
 
So...what can you do with that? ( I'm a noob).
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Old 04-22-2009, 11:34 AM Skadebo is offline  
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troyf4i
 
Where do you learn how to do this type of stuff? Say if I wanted to take a course at college to learn how to do that and other similarly simple projects.

And how much was the device to measure the wave?

I've been getting more and more interested in electronics and more and more frustrated at my lack of knowledge or experience.
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Old 04-22-2009, 12:02 PM troyf4i is offline  
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Whitebread
 
You can get schematics for a wide range of amps for various purposes on line very easily. I'm fairly sure you can use your computer as a scope for maybe 200 dollars. New, good scopes are upwards of 10K dollars. You may also want to get look used.
Almost forgot, some of the more expensive multimeters can read waveforms and can perform some simple o-scope functions. Honestly though, you don't really need more than a simple volt/ohm meter to build something simple like that.
Old 04-22-2009, 01:05 PM Whitebread is offline  
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Stoneman
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Quote:
Originally Posted by DigitalChaos View Post
any chance of posting the schematics and/or build plans?
cool stuff


the two bigger transistors that you can see in the picture are the two 3055's

Quote:
Originally Posted by [ Mr.Burn ] View Post
i'll also be doing a class on the principles of communication systems this summer Fourier Transforms here i come

Cool deal, I'm just finishing up a comm system class right now, I really liked it, esp all the topics that go into signal modification for transmitting and receiving, its nuts how many different things you can do to a signal.

I'm thinking about building two antennas this summer that can send and transmit a signal to each other, I bet that's right up your alley.

Quote:
Originally Posted by troyf4i View Post
Where do you learn how to do this type of stuff? Say if I wanted to take a course at college to learn how to do that and other similarly simple projects.

And how much was the device to measure the wave?

I've been getting more and more interested in electronics and more and more frustrated at my lack of knowledge or experience.

well, this was a project for my electronics 2 class that I'm just about finishing up with.

If you want to learn about electronics take a course on circuit analysis/theory and electronics. Be warned though there is A LOT to it, and unless you are majoring in it itd be hard to stuff down all the theory for design.

if you just want to make stuff on the weekends, I'd suggest buying a project book or looking for the simplest step by step projects on the internet. That way you can learn as you go about the specific type of things that you'd want to play around with. All you really need to know is basic ohms law and a little bit about transistors to build a lot of things out there.

oh and as far as the device that measures the voltage, it's called an oscope, pretty expensive they're all over the place at my school. If you are a college student no matter what your major is I'm sure your EE dept would let you use them in the lab if you asked nicely.

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Originally Posted by Skadebo View Post
So...what can you do with that? ( I'm a noob).

its an amplifier, you put in a signal and it will increase it.

think about a a cd player and a speaker, you put this little bad boy inbetween the two and it will play it louder most amps like this are used in much more complex circuits where a signal is very small and needs to be magnified in order to serve some greater purpose. If i really wanted an amp i'd really just buy one instead of making it myself as the one above is not too complicated.

unless I where an audiophile in which case I'd order all the custom parts to make the above type AB Amp out of tubes! They have almost zero distortion and really makes music sound like candy if you are that much of an audio head. those things are really freakin expensive to buy since those tubes are pretty much outdated. But i might build one in the future to see how good it sounds if anyone else would be interested in one
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Old 04-22-2009, 06:32 PM Stoneman is offline  
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Stoneman
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Quote:
Originally Posted by Whitebread View Post
You can get schematics for a wide range of amps for various purposes on line very easily. I'm fairly sure you can use your computer as a scope for maybe 200 dollars. New, good scopes are upwards of 10K dollars. You may also want to get look used.

Almost forgot, some of the more expensive multimeters can read waveforms and can perform some simple o-scope functions. Honestly though, you don't really need more than a simple volt/ohm meter to build something simple like that.

wow, any links as to software and hardware to use my computer as a scope? thatd be extremal helpful.

and you need a an scope instead of a multimeter to build the above amp because you have to adjust the first base resistor from the voltage divider circuit above the source to eliminate as much cross over distortion in the amplified signal as possible. Otherwise you wouldn't get your values as exact and you'd have a much of noise, you'd be better off just building an A class or a B class amp.
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Old 04-22-2009, 06:36 PM Stoneman is offline  
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tad
 
nice job man. welcome to being an engineer. pretty cool, ain't it? :-)
Old 04-22-2009, 06:55 PM tad is offline  
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Stoneman
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nice job man. welcome to being an engineer. pretty cool, ain't it? :-)

haha well, I have a semester or two left, but yes.

What discipline are you in?
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Old 04-22-2009, 08:30 PM Stoneman is offline  
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tad
 
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haha well, I have a semester or two left, but yes.

What discipline are you in?

computer & systems engineering... which at my school was basically EE w/o fields & waves and with a few comp sci courses added in.

I'm actually in a different profession now, but I still tinker all the time. You'd be amazed at how often weird info like this will come in handy in the future.
Old 04-22-2009, 08:40 PM tad is offline  
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MrCodeDude
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Quote:
Originally Posted by [ Mr.Burn ] View Post
i'll also be doing a class on the principles of communication systems this summer Fourier Transforms here i come
Fourier Transforms are pretty simple.

Quote:
Originally Posted by troyf4i View Post
Where do you learn how to do this type of stuff? Say if I wanted to take a course at college to learn how to do that and other similarly simple projects.

And how much was the device to measure the wave?

I've been getting more and more interested in electronics and more and more frustrated at my lack of knowledge or experience.
... if you want to learn all the theory behind the schematic posted, that's about 3/4 of a 4-year EE degree. If you have a schematic provided to you, you can just go to RadioShack and buy the parts, figure out the pin-outs and connect them together.

The oscilloscope we use in my Power Electronics lab is the Instek GDS-2204 and apparently it's $1800. They're not exactly cheap.
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