thebugger

modified 9 years ago

Beginners Amp

601

09:16:05

I'm sure any beginner started out with this type of amp. I know I did, and unsuccessfully If I may add. I didn't understand the amplifier classes back then and had it biased in a very ugly class B region (very cold). Anyway here you are, a very good (in regard to simplicity) class A amp with an output power of 3.5W. Not very much, but the output should be considerably clean and good-sounding. The transistors,  all but the two most right are BC550 for the NPN and BC560 for the PNP. The two most right transistors can be BD135 and BD136, but they'll be cutting real close to the maximum power dissipation, so more powerful transistors is beneficial but not necessary. To bias the amp correctly adjust the potentiometer until one of the output transistors draws around 1.1-1.2A. For the power supply I recommend using a laptop PSU, because they're regulated and quite resilient. That's it, plug and play

published 9 years ago

hurz

9 years ago

Plug and burn for beginner. More than 27/2 Watt in idle for BD's which are specified for max 12Watt and nothing said about a heatsink is a frustrating DIY project.

thebugger

9 years ago

You're mistaken, the power dissipation per device does not exceed 12W. It's around 11.5W, and with a sufficient heatsink a little overestimate won't hurt the devices. P.S. A heatsink for a 12W dissipation from such a small device should be considered by default

hurz

9 years ago

Wow, its 500mW below what the spec allows, LOL. All 4 BJTs at out stage are close to die. This to recommend for beginners is ridiculous. Why are you doing such nonsense?

hurz

9 years ago

Here your mistaken setup from yesterday, only to be precise http://everycircuit.com/circuit/4850407331594240 27Watt spillted on two BDs

thebugger

9 years ago

First of all, I'm beginning to think you completely lack practical experience and you're all about theory. Transistors can easily be pushed above their power rating without any problem whatsoever, that is, if proper heat extraction is present. Moreover the 2 driving transistors are well within proper levels dissipating no more than 160mW where the maximum dissipation is 500mW. The power transistors dissipate 11W out of the maximum 12.5W. With sufficient heatsink, the maximum ratings can be overstepped by a sufficient amount (up to 20-30%) without any problem whatsoever. So I suggest, you stop pulling shit out your ass, and give me some specific proof about your claims.

hurz

9 years ago

Build it and see what is does. You have no idea. You also missed a 22Ohm. The overall gain highly depends on input impedance. All this is nothing for a beginner! And you prove again that you are a beginner. At least you agree now that a heatsink is needed after i told you. Why are you doing this? And being rude doesn't help you to understand whats wrong with your circuit.

thebugger

9 years ago

Are you really this arrogant? Most of the users here hate you, cuz you only criticize, and most of the times it's just of of spite. The FACT is that all transistors are within operating parameters, and the heatsink is to be considered by default. There is absolutely nothing wrong with the circuit, and you know it :D You just can't accept the fact that people here don't like you, and you're constantly trying to take it out on the more advanced users, but this only serves to show just how pathetic you are. So yeah, I don't need to take your advices, they're only brought up by pure spite, and the circuit is perfect for a beginner, and well within parameters ;). The gain can be reduced further by an AC NFB but I chose not to complicate the circuit further.

thebugger

9 years ago

And P.S. I'm only being rude in response to your arrogance ;)

hurz

9 years ago

Most users like my circuits and only some idiots are jealous about my knowledge, right. The FACT you haven't said anything about the heatsinks shows you never build this circuit, or do you know you can use one big one? How arrogant a beginner must be to talk about a "beginner amp". You dont even see the problem with your strange NFB.

thebugger

9 years ago

I can't deal with you really! No one likes you because you're a complete stuck up. You're pulling shit out your ass, just to prove someone wrong, and when you're proven wrong, you just vanish out of the comments. Dude, I really don't want you to comment on my circuits, ok?

hurz

9 years ago

I cant see how you talking about electronic... Again, being rude wont help you.

Robert_Kidd

9 years ago

Hurz, NO ONE appreciates or is interested in your POINTLESS comments. You are SO insecure you try to big yourself up by making negative comments about other people's circuits. Most would know a heat sink was required and, if not, they'd soon realise it. IT'S CALLED LEARNING! And no, I'm not 'sucking up' to the Bug. He and I have differences of opinion but we remain civil and don't need to exchange insults. Why don't you learn?

thebugger

9 years ago

Hear hear!

hurz

9 years ago

Buggzy said "plug and play" and i just said "plug and burn". And who is not civil in this thread here? Anything constructive to tell/show us here Robbi_Kiddi?

hurz

9 years ago

Meanwhile the troll appears, i have put 18Watt load on a 400cm² and 2mm strong aluminium. This heatsup within a few minutes to 80°C -"beginner amps" does look different, and beginners do mistakes, but frauds do stupid "beginner" circuit-descriptions, like the troll.

hurz

9 years ago

That's it, plug and play

Robert_Kidd

9 years ago

First, I don't care if you refer to me as a troll. People can see I'm not. But, again you miss the point. I can tell the Bug that "Hear hear" in correct English is "Here here". He won't insult me for correcting him. He may even thank me for helping with his English (which is really very good) - I don't speak a word of his language. Your opening comment 'Plug & Burn', whether correct or not, is offensive. Possibly you do not mean it to be? But it is anyway! Can't you see how you immediately (often) offend people like this?

hurz

9 years ago

Trolls and bootlickers are not welcome.

hurz

9 years ago

BTW, "hear hear" does sounds for me better

Robert_Kidd

9 years ago

Then why are you on EC?

Robert_Kidd

9 years ago

BTW, it doesn't matter what you think sounds better! It's what is correct - after all you insist on telling everyone what's best - your opinion!!

thebugger

9 years ago

I think it's Hear Hear actually , but that's irrelevant. The fact is that 12W is not really that much actually, and a normal sized heatsink will easily dissipate it. Furthermore every single device I noted as appropriate, does in fact not exceed its datasheet specified ratings. And every sensible user will put a heatsink, I really didn't deem it necessary to note. So if there isn't anything else you need to say, I'd like to close the discussion

Robert_Kidd

9 years ago

I was jesting and using it to make a point that you wouldn't get upset about being corrected. It's of parliamentary origin, Hear him, Hear him. I agree with you on circuit but one day (don't hold your breath) I will build it and see what temperatures I get with a reasonable heat sink. Thread closed from here :-)

hurz

9 years ago

Setup from todays configuration burns 22W which a "sensible" beginner has to bring on a "reasonable" heat sink. Without heat sink this circuit description ends up in "plug and burn" Have fun with electronic. Thread closed

zorgrian

9 years ago

NO the thread is not closed as I must say that apart from the need for heat dissipation, this circuit could do with modification or a rethink. I say this bcuase it doesn't seem to be very efficient

zorgrian

9 years ago

I mean it will work but I would not pick BD135 transistors... this design might be better if the transistors were more hefty and if you are going to build this type of amplifier then maybe make it with decent transistors and a higher voltage or better split rail... just my thoughts on push pull amps - I have made a fair number of them

thebugger

9 years ago

Yeah, but the idea is to use the simplest materials you could find. That's why I noted in the description that with BD136 you'll be cutting close to the power ratings and you should use a little more powerful transistors, but it's not absolutely necessary, because even though you'll be close to the power maximum, you'll still be below it, and frankly, you can run transistors, at higher currents without a problem, as long as you cool it off nicely. And yeah it's not efficient, just the miserable 14%, but it's in class A and you can't really expect much more, unless tranaformer coupling is used. You can always improve the efficiency by pushing it in class B, where I measured efficiency of >50%, but that's just how I decided to present the circuit.

thebugger

9 years ago

And yeah zorg, I agree, split rail amps are the best. The output capacitor of single rail amps, shortens the bandwidth, induces distortion, and doesn't particularly like square wave signals.

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