OOMPH is power.
The output transistors in the class-AB circuit don't have enough base current to drive an 8 ohm speaker properly.

Electromaster fixed the software bug that caused the temporary attachment quota problem.

Class C is used in radio circuits where an LC tuned circuit removes the harmonics that are caused. Class-C would cause severe distortion (lots of harmonics) in an audio amplifier.
Class-D amplifiers have a very complicated high frequency pulse-width-modulation switching circuit.

There are sites that host your schematics and pictures. Some of them have horrible pop-up ads. Some of them take forever to wake up.

Here is a simulation of Hero's modifications:

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Uncle $crooge

 

Here's a slightly improved version, it's not perfect or efficient but it has lower bias resistors for more power and negative feedback (provided by R1 to R3) to remove the distortion.

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Attached Files

poweramp.asc (2.2 KB, 10 views)

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

Hi Hero,
Your modified amp is much better.
Except its voltage gain is very low (2.6) and its input impedance is very low (about 2k).

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Uncle $crooge

 

hi agu,
If you have not already got this link, I think you may find it useful.

INTRODUCTION TO DIGITAL FILTERS WITH AUDIO APPLICATIONS

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Eric " Good enough is Perfect "
I will NOT answer PM's requesting technical help, please use the Forum
PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/

 

Hi Eric,
Thanks but no thanks.
The article is for mathamaticians who are designing ICs. I haven't used math for many years and I have never designed an IC.

I designed audio filters with opamps. I worked with products with DSP ICs that had programmed filters.

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Uncle $crooge

 

That's what negative feedback does for you but at least it will drive the speaker, there's no distortion and you need to add a pre-amplifier to make this circuit useful.

You could make Q1 a darlington and R1 1M if you want more gain.

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Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

i have just downloaded the file couldnt get online all this time.listen here is a different transistor switch i found something like this in the forum.for the one on the left it was said that the led wud light if the base was driven low and for the right it was said that it would light when the base was driven high.i have measured the voltage and the currents as seen in the picture also can you tell me how its working.i understand the first one because npn sinks current correct me if i am wrong? and what is thje reason for the humangous current in the right hand side circuit??

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No. The LED and the transistor would burn out as shown without a current-limiting resistor. The 10k resistor applies base current to the transistor to turn it on. Then the base is about +0.7V. If you connect the base to 0V then the transistor will turn off.

You had the LED connected directly across the battery so it would burn out instantly. You had the transistor connected so that it shorts the battery and burns out.
My corrected circuit shows a current-limiting resistor in series with the LEDs.
The circuit on the right has the transistor connected as an emitter-follower so that its emitter is about +11V as shown and if the base is connected to 0V then the transistor turns off.

Did you notice that on my schematic there are no wires running all over the place and no wires cross?

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Uncle $crooge

 

I comfused, I thought this thread was supposed to be about an audio amplifier not switching LEDs?

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

Yeah, Wond3rboy hijacked Patroclus' thread, but he appears to have abandoned it.

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Ron

 

Hero999 sorry for that but since you didnt carry on with the thread so i thought why not continue to learn from it rather than starting a new thread

 

hey audioguru,can you tell me how did you calculate the i/p impedence of heros amp.i mean you cal the i/p impedence of the ce amp and then how did you calculate the ab amps i/p impedence and what about the o/p impedence of the ce amp cuase it is also seen by the power amp.

 

I just guessed. In the simulation the input impedance is 1360 ohms.

The input impedance of a common-emitter transistor is hFE times its internal re plus hFE times its RE, then any biasing resistors in parallel.
The internal re of a silicon transistor is 0.026/emitter current in milliamps.

The output impedance of a common emitter transistor is its collector resistor. The transistor itself is a current-sink with a very high impedance. Negative feedback from the output to the input reduces the input impedance and reduces the output impedance.

The output impedance of Hero's amplifier is so low that it cannot be measured on the simulation. Most good power amplifiers have an output impedance of 0.04 ohms or less at low frequencies.

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Uncle $crooge

 

thank you very much!
can you tell me some other things i am supposed to work at inorder to improve my electronic skills?

 

One more question:What is hte effect of bootstrapping an amplifier except reducing the impedence of an amplifier?