Basics on constructing an amplifier

tigox

Member
2012-07-10 7:24 pm
Hey all :D i've fixed a lot of amplifiers, and set them up, but i would like to build my one amplifiers, because i can me one to exactly match my needs, so can someone please explain some of the basics of amplifiers? like what are coupling and decoupling capacitors, why are there so much resistors on an amplifier besides the input resistors, and what are the other capacitors you see at the output of the amplifier?
Thank you very much :DD
 
You understand that the question you asked is almost impossible to answer in a few words on a forum?

You could find out much of what you want to know by reading EVERYTHING on this very good site about amplifier design:-Elliott Sound Products - Audio Power Amplifier Design Guidelines

If you cannot understand the site, you can find explanations of nearly everything using google and wikipedia.
 

jcx

Member
2003-02-17 7:38 pm
..
Last edited:
If you don't understand the basics of the circuit, you're going to be lost when it comes time to debug it. You're also going to have a hard time designing one that "exactly matches your needs" if you don't know what a decoupling capacitor etc is.

If you want to learn some basics of layout and debugging, build something simple like an 1875 chip amp. Learn what every component is for (there's only a few), debug it, tweak it. You will learn a lot.

The Elliott website has some old circuits in there for illustrative purposes. Breadboard and debug some of these. If you can't set up and debug a simple emitter follower circuit, you will never know how to implement and modify somebody else's circuits for your own purposes.
 
I'm getting deja vu trying to explain this to you. You seem to have a notion that resistors are "bad" in a circuit.

I tried many decades ago to teach a guy how to design and build an amplifier. This was before there were any practical op amps for hobbyists to use in audio circuits (either terrible or way too cranky). His philosophy was that resistors "wasted power" and that it would be better if you just connected all the transistors together. It never went far because he could never get over his preconcieved notions.

Do you understand a basic non-inverting amplifier? How about an inverting amplifier? Start there.
 

tigox

Member
2012-07-10 7:24 pm
I am soory, i have wasted your time ... i will inform myself more on this subject by myself :S

but yeah you're right, as a second year student, i was basically "teached" that resistors "lower" values, so there's a natural association in my brain that resistors are bad in amplifier, except for filtering signals
 
I think a good place to start would be to learn about the various parameters of opamps and what the differences are for a quality component.

I wouldn't use LM741 in a circuit even if it was designed to make noise.
I would be tempted to not even use one in a battery charger circuit!!!

The old tried and true TL072/082 would be a better place to start.
Especially in audio!!!
Or even better the ole NE5532 not to mention some of today's newer devices that are available.

You are on the right track as you can parallel opamp's but it takes a bit more circuitry in order to make them work properly and be stable without any oscillations.
The circuit you posted would not even come close to having a useable output, if any at all.

Keep reading as this is a wonderful hobby.
All you need to do is learn a few basics using opamp's and some general rules in how to make them work.

That would be the first place to start before you can even think about designing a power amplifier.

Get LTspice it is free and you can build circuits in it and see if it is going to work before you go end up spending a lot of money on parts that only produce some magic blue smoke!!

Circuitmaker2000 or the free student version Circuitmaker6 is another great aged piece of software that is easy to use and can be found on the web.
I still use the Circuitmaker stuff nearly everyday !!

FWIW

jer :)
 
Last edited:
I am soory, i have wasted your time ... i will inform myself more on this subject by myself :S

I can hope that the replies made you think a little bit.

I don't feel like my time is wasted if you learned something. No need for apologies.

It seems like you have a clue about putting different circuits together for a desired result. In fact custom circuits are basically just "building blocks" like buffers, non-inverting amps, etc configured together for a desired result.

What you are lacking is knowledge of these basic circuits. You can't build a bridge amp until you're solid on building the "gainclone" "building blocks" that comprise it. So build a single ended chip amp; tweak it, mod it, understand it. Then move on to the next step.